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Students can Download Chapter 6 Breathing and Exchange of Gases Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 6 Breathing and Exchange of Gases

What is respiration?
The process of exchange of O₂ from the atmosphere with CO₂ produced by the cells is called breathing, commonly known as respiration.

RESPIRATORY ORGANS:

Human Respiratory System:
The nostrils leads to a nasal chamber through the nasal passage. The nasal chamber opens into nasopharynx the common passage for food and air. Nasopharynx opens through glottis of the larynx region into the trachea.

Sound box in respiratory system:
Larynx is a cartilaginous box which helps in sound production called as the sound box. Glottis is covered by a thin elastic cartilaginous flap called epiglottis to prevent the entry of food into the larynx. Trachea is a straight tube which divides into a right and left primary bronchi.

Each bronchi undergoes repeated divisions to form the secondary and tertiary bronchi and bronchioles ending up in very thin terminal bronchioles.
Each terminal bronchiole gives rise to vascularised bag-like structures called alveoli. The branching network of bronchi, bronchioles and alveoli comprise the lungs.

The two lungs which are covered by a double layered pleura, with pleural fluid between them. It reduces friction on the lung surface. The conducting part transports the atmospheric air to the alveoli. Exchange part is the site of diffusion of O₂ and CO₂ between blood and atmospheric air.

Where is lung fitted in human body?
The lungs are situated in the thoracic chamber which is formed dorsally by the vertebral column, ventrally by the sternum, laterally by the ribs and on the lower side by the dome-shaped diaphragm. The anatomical setup of lungs in thorax is the arrangement essential for breathing, directly alterthe pulmonary volume.

Respiration involves the following steps:

• Breathing or pulmonary ventilation by which atmospheric air is drawn in and CO₂ rich alveolar air is released out.
• Diffusion of gases (O₂ and CO₂) across alveolar membrane.
• Transport of gases by the blood.
• Diffusion of O₂ and.CO₂ between blood and tissues.
• Utilisation of O₂ by the cells for catabolic reactions and resultant release of CO₂

MECHANISM OF BREATHING:
Breathing involves two stages:

1. Inspiration during which atmospheric air is drawn in and
2. Expiration by which the alveolar air is released out.

How does increase or decrease of pulmonary volume occur?
Inspiration is initiated by the contraction of diaphragm which increases the volume of thoracic chamber .The contraction of external inter-costal muscles lifts up the ribs and the sternum causing an increase in the volume of the thoracic chamber. It increase the pulmonary volume.

An increase in pulmonary volume decreases the intra-pulmonary pressure to less than the atmospheric pressure which forces the airfrom outside to move into the lungs,i.e., inspiration Relaxation of the diaphragm and the inter-costal muscles returns the diaphragm and sternum to their normal positions and reduce the thoracic volume.

It reduce the pulmonary volume. This leads to an increase in intra-pulmonary pressure to slightly above the atmospheric pressure causing the expulsion of airfrom the lungs, i.e., expiration.

Instrument used for measuring breathing movements:
A healthy human breathes 12 – 16 times/minute. The volume of air involved in breathing movements can be estimated by using a spirometer.

Respiratory Volumes and Capacities:

EXCHANGE OF GASES:
Alveoli are the sites of exchange of gases. O₂ and CO₂ are exchanged in these sites by simple diffusion.
Rate of diffusion:
Solubility of the gases and the thickness of the membranes are the important factors that affect the rate of diffusion.

Partial pressure of gases:
Pressure contributed by an individual gas in a mixture of gases is called partial pressure and is represented as pO₂ for oxygen and pCO₂ for carbon dioxide. As the solubility of CO₂ is 20 – 25 times higher than that of O₂, the amount of CO₂ that can diffuse through the diffusion membrane.

As the solubility of CO₂ is 20 – 25 times higher than that of O₂ the amount of CO₂ that can diffuse through the diffusion membrane.

The diffusion membrane is made up of three major layers such as

Its total thickness is much less than a millimetre.

TRANSPORT OF GASES:
Blood is the medium of transport for 02 and C02.

1. About 97 per cent of O₂ is transported by RBCs in the blood.
2. The remaining 3 per cent of O₂ is carried in a dissolved state through the plasma.
3. Nearly 20 – 25 per cent of CO₂ is transported by RBCs whereas 70 per cent of it is carried as bicarbonate.
4. About 7 per cent of CO₂ is carried in a dissolved state through plasma.

Transport of Oxygen:
O₂ bind with haemoglobin to form oxyhaemoglobin. Each haemoglobin molecule can carry a maximum of four molecules of O₂. Binding of oxygen with haemoglobin is related to partial pressure of O₂.

Oxygen dissociation curve is useful in studying the effect of factors like pCO₂, H⁺ concentration, etc., on binding of O₂ with haemoglobin.

Therefore O₂ gets bound to haemoglobin in the lung surface and gets dissociated at the tissues.

Transport of Carbon dioxide:
CO₂ is carried by haemoglobin as carbamino-haemoglobin (about 20 – 25 per cent). This binding is related to the partial pressure of CO₂. When pCO₂ is high and pO₂ is low as in the tissues, more binding of carbon dioxide occurs whereas, when the PCO₂ is low and pCO₂ is high as in the alveoli, dissociation of CO₂ from carbamino-haemoglobin takes place. RBCs contain a very high concentration of the enzyme, carbonic anhydrase which facilitates the reaction in both directions.

At the tissue site where partial pressure of CO₂ is high due to catabolism, CO₂ diffuses into blood (RBCs and plasma) and forms HCO₂ and H⁺. At the alveolar site where pCO₂ is low, the reaction proceeds in the opposite direction leading to the formation 0f CO₂ and H₂O. Every 100 ml of deoxygenated blood delivers approximately 4 ml of CO₂ to the alveoli.

Students can Download Chapter 13 Kinetic Theory Notes, Plus One Physics Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Physics Notes Chapter 13 Kinetic Theory

Summary
Introduction
The kinetic theory was developed in the nineteenth century by Maxwell, Boltzmann and other. It gives a molecular interpretation of pressure and temperature of a gas. It also explains gas laws and Avogadro’s hypothesis. It correctly explains specific heat capacities of many gases. It help us to find molecular sizes and masses.

Molecular Nature Of Matter
The scientific atomic theory is credited to John Dalton. Atomic theory is not the end of quest, but the beginning. Atoms consist of a nucleons and electrons. The nucleous itself is made up of protons and neutrons. The protons and neutrons are again made up of quarks. Even quarks may not be the end of the story.

There may be string-like elementary entities. In this chapter we shall limit ourselves to understanding the behavior of gases.

Behavior Of Gases
Gas Laws
1. Boyles law
The law states that at a given temperature, the volume of a given mass of gas varies inversely as its pressure.
It can be written as
\(P a \frac{1}{V}\) (at constant T)
PV = constant
PV = μ RT
μ → No. of moles, R → universal gas constant, T → temperature
Boyles law is not obeyed by gasses at all temperatures and pressure. Usually, Boyles, law is obeyed by gases at high temperature and low pressure (Graph is given below).

A real gas which obey this law is called ideal or perfect gas.

Variation of ‘R’ \(\left(=\frac{\mathrm{PV}}{\mathrm{T}}\right)\) with Pressure (for different temperatures)

Variation of R \(\left(=\frac{\mathrm{PV}}{\mathrm{T}}\right)\) with Pressure for temperature T₁ > T₂ > T₃ is shown in the above graph. The above graph shows that, all real gases approach ideal gas behavior at low pressure and high temperature.

At low pressure or high temperature, the molecules are for apart and molecular interactions are negligible. Without interactions the gas behaves like an ideal gas.

Note:
R = 8.324 J mol^-1 k^-1.
Variation of V with P for different temperature:

The above graph shows experimental PV curves for steam at three temperature The dotted line are the theoretical curves. (According to Boyles law). The theoretical value and experimental value comes in agreement at high temperatures and low pressures.

2. Charles law
Charles law states that the volume of a given mass of gas is proportional to its temperature when its pressure is kept constant.
V a T (P is constant)
i.e.,

The graph between V and T:

The above graph shows experimental T-V curves (solid lines) for Co₂ at three pressures compared with Charles law (dotted lines). T is in unit of 300 k and V in units of 0.13 litres.

Question 1.
Why theoretical value does not agree with experimental value?
Answer:
According to Charles law the graph between T and V is straight line. It means that when temperature decreases, the volume of gas decreases and finally becomes zero.

Practically volume will not be zero. Because the molecules require some finite space to exist. This implies that we cannot reduce its temperature to zero value. A zero kelvin temperature is only an idealized concept.

Dalton’s law of Partial Pressures:
It states that, the total pressure of a mixture of ideal gases is the sum of partial pressures.

Proof:
Consider a mixture of non-interacting ideal gases. μ₁, moles of gas 1, μ₂ moles of gas 2 etc. in a vessel of volume V at temperature T and pressure P. Using Boyles law, we can write
PV = (μ₁ + μ₂ +…………..)RT
P = \(\frac{\mu_{1} \mathrm{RT}}{\mathrm{V}}+\frac{\mu_{2} R T}{V}+\ldots \ldots \ldots\)
P = P₁ + P₂ +……………………

Kinetic Theory Of An Ideal Gas
The kinetic theory of gases has been developed by Clausius, Maxwell, Boltzmann and others. The theory is based on the following postulates.

• The gas is a collection of large number of molecules. The molecules are perfectly elastic hard spheres.
• The size of a molecule is negligible compared with the distance between the molecules.
• The molecules are always in random motion
• During their motion, the molecules collide with each other and with the walls of the containing vessel.
• The collisions are elastic and hence the total K.E energy and the total momentum of the colliding molecules before and after collisions are the same.
• The kinetic energy of a molecule is proportional to the absolute temperature of the gas.
• There is no force of attraction or repulsion between molecules.

The pressure of an ideal gas:

Consider molecules of gas in a container. The molecules are moving in random directions with velocity V. This is the velocity of a molecule in any direction. The velocity V can be resolved along x, y and z directions as V_x, V_y, and V_z respectively.

If we assume a molecule hits the area A of the container with velocity V_x and rebounds back with -V_x. (The velocities V_x and V_y do not change because this collision is perfectly an elastic one).

Therefore, the change in momentum imparted to the area A by the molecule
= mv_x^– – mV_x
= 2mV_x

To find the total number of collisions taking place in a time t, consider the motion of the molecules towards the wall. The molecules covers a distance V_xt along the x direction in a time t. All the molecules within the volume AV_xt will collide with the area in a time t.

If ‘n’ is the number of molecules per unit volume, the total number of molecules hitting the area A,
N = AV_xt n.

But on an average, only half of those molecules will be hitting the area, and the remaining molecules will be moving away from the area. Hence the momentum imported to the area in a time t
Q = 2mv_x × \(\frac{1}{2}\) AV_xtn.
= nmV_x²At
The rate of change of momentum,
\(\frac{Q}{t}\) = nmV_x²A
But rate of change of momentum is called force, ie. force F = nmV_x²A
∴ Pressure P = nmV_x² (P = \(\frac{F}{A}\))
Different molecules move with different velocities. Therefore, the average value V_x² is to be taken. If \(\overline{\mathbf{v}}_{\mathbf{x}}^{2}\) is the average value then the pressure.

\(p=n m \bar{v}_{x}^{2}\) ……………….. (1)

\(\overline{\mathbf{v}}_{\mathbf{x}}^{2}\) is known as the mean square velocity. Since the gas is isotropic (having the same properties in all directions), we can write

Kinetic Interpretation of gas laws:

Question 2.
Derive the ideal gas equation from P = \(\frac{1}{3} \mathrm{nm} \overline{\mathrm{v}}^{2}\)
Answer:
The average kinetic energy of the molecule is
KE = \(\frac{1}{2} m \bar{v}^{2}\) …………………….(3)
The eq (2) can be modified as

The average Kinetic energy of a molecule remains constant when the temperature is constant. That is when the temperature varies, \(\overline{\mathrm{KE}}\) also varies accordingly. The kinetic energy of a molecule is related to its absolute temperature by an equation
\(\overline{\mathrm{KE}}\) = \(\frac{3}{2}\)K_BT
Substitute equation (5) in equation (6); we get

N = μ N₀
P V = μ N₀K_BT
P V = μ R T…………………… (8)
(N_BK_B = R)
This is the ideal gas equation

Deduction of Boyles law:
If the temperature is constant for gas, the eq (8) can be written as
PV = Constant
This is called Boyles law

Deduction of Charles law:
If pressure of a gas is constant, the eq (8) can be written as
V a T

This is called Charles law.

Deduction of Avogadro’s Hypothesis:
If P₁, T₁, and V constant, N₀ will be constant, ie. equal Volumes of all gases, under the same conditions of pressure and temperature will contain the same number of molecules. This is known as Avogadro’s hypothesis.

Law Of Equipartion Of Energy
Degrees of freedom:
Degrees of freedom is number of independent ways by which a molecule can possess kinetic energy of translation, rotation and vibration.

Law of equipartition energy:
The total kinetic energy of a molecule is equally divided among the different degrees of freedom.

K.E. per degree of freedom:
The average energy per degree of freedom

Where K_B is Boltzman constant.

Degrees of freedom and energy of monoatomic gas:
A monoatomic atom has 3 degrees of freedom, ie; it can move in x, y and z-direction. The average energy of single monoatomic gas in the x-direction,

Note:
1. If a molecule is restricted to move in plane. It has 2 degrees of freedom.
2. If a molecule is restricted to move in a line, it has only 1 degrees of freedom.

Degrees of freedom and energy of single diatomic molecule (rigid rotator)

Consider a diatomic molecule as a rigid rotator (Rigid rotator means that the molecule does not vibrate). A rigid diatomic molecule has 3 translation degrees of freedom and 2 rotational degrees of freedom.
(Rotational degrees of freedom is shown in the above figure).
∴ Total average energy of diatomic rigid rotator,

Note:
A diatomic molecule has 3 rotational degrees of freedom. But we consider only 2 degrees of freedom. We neglect rotation along the line joining the atoms. Because it has very small moment of inertia.

Degrees of freedom and energy of single diatomic molecule of nonrigid rotator:
Molecules like ‘co’ even at moderate temperatures have a mode of vibration. The vibration energy of a diatomic molecule.

Where K is the force constant of the oscillator and y the vibrational coordinate. The vibration energy mode contain two terms (1) Kinetic energy (2) Potential energy. Hence a single mode of vibration of molecule is considered as 2 degrees of freedom (potential energy and kinetic energy)
∴ The total vibrational energy of a single-mode
= 2 × \(\frac{1}{2}\)K_BT
= K_BT
∴ The total energy of diatomic nonrigid rotator

Degrees of freedom and energy of polyatomic molecule, (non- rigid rotator):
If a polyatomic molecule has ‘f’ modes of vibration, total number of degrees freedom = 3 vibration + 3 rotator+f vibration.
∴ Total average energy of single polyatomic molecule,

Specific Heat Capacity
Monoatomic Gases (Molar specific heat capacity):
The energy of a single monoatomic gas = 3 × \(\frac{1}{2}\) K_BT
The energy of one mole monoatomic gas = 3 × \(\frac{1}{2}\) K_BT × N_A
[one-mole atom contain Avogadro number (N_A) of atoms]

A Diatomic Gas (Molar specific heat capacity):
A rigid diatomic molecule has 5 degrees of freedom : 3 translational and 2 rotational.
∴ energy of single diatomic (rigid) molecule = 5 × \(\frac{1}{2}\) K_BT
for one mole of diatomic molecule, energy U = 5 × \(\frac{1}{2}\) K_BT × N_A

Nonrigid diatomic molecule having a vibrational mode (Molar specific heat capacity):
If the diatomic molecule is not rigid but has a vibration mode. The energy of one mole,

Polyatomic Gas (Molar specific heat capacity):
In general a polyatomic molecule has 3 translational, 3 rotational degrees of freedom and a certain number (t) of vibrational modes.

The energy of one mole polyatomic gas,

Note: The experimental value of C_P and C_V of polyatomic gases are greater than the predicted values. The theoretical value and experimental value will be equal when we include vibrational modes of motion in the calculation.

Specific heat capacity of solids:
Consider a solid of N atoms. Each atom is vibrating about its mean position. Each vibration mode has two degrees of freedom (corresponding to potential energy and kinetic energy). Hence an oscillation in one dimension has average energy of

2 × \(\frac{1}{2}\) K_BT = K_BT
∴ Total energy in three dimension
= 3 × K_BT
= 3K_BT.

For one mole of solid, total energy,
U = 3K_BT × N_A
[N_A = Avagadro number]
= 3N_AK_BT
U = 3RT …………………. (1) [∴ R = K_BN_A].
We know specific heat capacity,

Note:
In solids, we do not consider the translational and rotational degrees of freedom. We consider only vibrational degrees of freedom.

Specific heat capacity of water:
We treat water like a solid. A water molecule has 3 atoms. Each atom in the molecule is vibrating about its mean position. A single vibration mode has 2 degrees of freedom (1) potential energy (2) kinetic energy.

ie; The energy of one atom in one dimensional vibration mode =
2 × \(\frac{1}{2}\) K_BT = K_BT

The energy of one atom having 3 dimensional vibration mode = 3 × K_BT
The energy of one H₂0 molecule having 3 dimension vibration mode
U = 3 × 3K_BT × N_A
U = 9RT [∵ R = K_B N_A]
∴ Specific heat capacity,
\(\mathrm{c}=\frac{\mathrm{dU}}{\mathrm{dT}}=\frac{\mathrm{d}}{\mathrm{dT}}(\mathrm{RT})\)
C = 9R.

Mean Free Path
Molecules in a gas have large speeds. Yet a gas leaking from a cylinder in a kitchen takes considerable time to diffuse to the other corners of the room. Why?

The molecules in a gas have a finite size. So they collide with other molecules during their motion. As a result, they cannot move straight like path. Their paths are continuously deflected.

Mean free path:
The mean free path is the average distance covered by a molecule between two successive collisions.

Expression for mean free path:

Suppose the molecules of a gas are spheres with diameterd. Let 〈v〉 be the average velocity of the molecule.
The volume covered by a molecule during its motion, in a time Δt = πd² 〈v〉 Δt.
If ‘n’ is the number of molecules per unit volume, the total number of molecules in the above volume
= πd² 〈v〉 Δt n.
The number collisions in a time Dt,
= πd² 〈v〉 Δt n.
Number of collisions in one second,
= n π d² 〈v〉
∴ The time between two successive collisions,
\(\tau=\frac{1}{n \pi d^{2}\langle v\rangle}\).
The average distance between two successive collisions,

In this derivation, we imagined the other molecules to be rest. But actually all other molecules are moving. Hence we must take relative velocity 〈v_r〉 instead of 〈v〉. A more exact treatment gives
\(\ell=\frac{1}{\sqrt{2} \mathrm{n} \pi \mathrm{d}^{2}} \dots(1)\)
The mean free path given by the above equation depends inversely on the number density and the size of the molecule.

Students can Download Chapter 5 Digestion and Absorption Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 5 Digestion and Absorption

What is digestion?
This process of conversion of complex food substances to simple absorbable forms is called digestion.

DIGESTIVE SYSTEM:
It includes

• Alimentary canal
• Associated glands.

Alimentary canal:

The human digestive system
1. The alimentary canal begins with the mouth, and it leadsto the buccal cavity or oral cavity.

2. The oral cavity has a number of teeth and a musculartongue. Each tooth is embedded in a socket of jaw bone. This type of attachment is called thecodont.

3. Human being forms two sets of teeth during their life, a set of temporary milk or deciduous teeth replaced by a set of permanent or adult teeth. This type of dentition is called diphyodont.

Dental formula of adult human
An adult human has 32 permanent teeth which are of four different types (Heterodont dentition).

• incisors (I)
• canine (C)
• premolars (PM)
• molars (M).

Arrangement of teeth in each half of the upper and lower jaw in the order I, C, PM, M is represented by a dental formula which in human is
\(\frac{2123}{2123}\)

• The hardest part of teeth is made up of enamel, helps in the mastication oWood.
• The tongue is attached to the floor of the oral cavity by the frenulum.
• The upper surface of the tongue has small projections called papillae, some of which bear taste buds.
• The oral cavity leads pharynx which serves as a common passage for food and air.
• The oesophagus and the trachea (wind pipe) open into the pharynx.
• A cartilaginous flap called epiglottis prevents the entry of food into the glottis – opening of the wind pipe – during swallowing.
• The oesophagus is a thin, long tube which passing through the neck, thorax and diaphragm and leads to a ‘J’ shaped bag like structure called stomach.
• A muscular sphincter (gastro-oesophageal) regulates the opening of oesophagus into the stomach.

The stomach, located in the upper left portion of The abdominal cavity, has three major parts:

1. A cardiac portion into which the oesophagus opens
2. A fundic region and
3. A pyloric portion which opens into the first part of small intestine

Small intestine is distinguishable into three regions:

1. A ‘U’ shaped duodenum
2. A long coiled middle portion jejunum and
3. A highly coiled ileum

The opening of the stomach into the duodenum is guarded by the pyloric A sphincter. Ileum opens into the large intestine.

Large intestine:
It consists of

• caecum
• colon
• rectum.

Caecum:
It is a small blind sac consists of some symbiotic micro-organisms. A narrow finger-like tubular projection, the vermiform appendix which is a vestigial organ, arises from the caecum. The caecum opens into the colon.

colon:
It is divided into three parts-an ascending, a transverse and a descending part. The descending part opens into the Rectum.

Rectum: It opens out through the anus.
Wall layers of alimentary canal:
It consists of four layers namely

1. Serosa
2. muscularis
3. sub-mucosa &
4. mucosa.

1. Serosa is the outermost layer and is made up of a thin mesothelium with some connective tissues.
2. Muscularis is formed by smooth muscles
3. The submucosal layer is formed of loose connective tissues containing nerves, blood and lymph vessels.
4. The innermost layer lining of the alimentary canal is the mucosa.
   • In duodenum, glands are also present in sub-mucosa.
   • Mucosa forms irregular folds (rugae) in the stomach and small finger-like foldings called villi in the small intestine
   • The cells lining the villi produce numerous projections called microvilli giving a brush border appearance.
   • These modifications increase the surface area.
   • Villi are supplied with a network of capillaries and a large lymph vessel called the lacteal.
   • Mucosal epithelium has goblet cells which secrete mucus that help in lubrication.
   • Mucosa also forms glands in the stomach (gastric glands) and crypts in between the bases of villi in the intestine (crypts of Lieberkuhn).

Digestive Glands:
It includes

1. salivary glands
2. liver
3. pancreas.

1. Salivary glands:
Saliva is mainly produced by three pairs of salivary glands

• parotids (cheek)
• sub-maxillary/sub-mandibular (lower jaw)
• sublinguals (belowthe tongue).

The duct systems of liver, gall bladder and pancreas These glands situated just outside the buccal cavity secrete salivary juice into the buccal cavity.

2. Liver:

• It is the largest gland of the body weighing about 1.2 to 1.5 kg in an adult human.
• It is situated in the abdominal cavity, just below the diaphragm and has two lobes.
• The hepatic lobules are the structural andfunctional units of liver containing hepatic cells arranged in the form of cords.
• Each lobule is covered by a thin connective tissue sheath called the Glisson’s capsule.
• The bile secreted by the hepatic cells passes through the hepatic ducts and is stored in gall bladder.
• The duct of gall bladder (cystic duct) along with the hepatic duct from the liver forms the common bile. duct
• The bile duct and the pancreatic duct open together into the duodenum which is guarded by sphincter of Oddi.

3. Pancreas:
It is a heterocrine (both exocrine and endocrine) elongated organ situated between the limbs of the ‘U’ shaped duodenum.

Secretions of exocrine and endocrine:

• The exocrine portion secretes an alkaline pancreatic juice containing enzymes
• The endocrine portion secretes hormones, insulin and glucagons.

DIGESTION OF FOOD:

1. The process of digestion is accomplished by mechanical and chemical processes.
2. The teeth and the tongue with the help of saliva masticate and mix up the food thoroughly. *Mucus in saliva helps in lubricating and adhering the masticated food particles into a bolus.

Contents of saliva:
It contains electrolytes (Na⁺, K+⁺, Cl^–, HCO^–“) and enzymes, salivary amylase and lysozyme.
The chemical process of digestion is initiated in the oral cavity by the carbohydrate splitting enzyme, the salivary amylase( pH 6.8).

Digestion of starch:
About 30 percent of starch is hydrolysed here by salivary amylase (optimum pH 6.8) into a disaccharide -maltose.

Enzyme for preventing infections:
Lysozyme present in saliva acts as an antibacterial agent that prevents infections.

• The bolus is then passed into the pharynx and then into the oesophagus by swallowing or deglutition.
• The bolus further passes down through the oesophagus by successive waves of muscular contractions called peristalsis.
• The gastro-oesophageal sphincter controls the passage of food into the stomach.

Mucosa of stomach and gastric glands:
Gastric glands have three major types of cells namely

Digestion in stomach:
1. The food mixes thoroughly with the acidic gastric juice of the stomach by the churning movements of its muscular wall and is called the chyme.

2. The proenzyme pepsinogen, in the presence hydrochloric acid gets converted into the active enzyme pepsin, the proteolytic enzyme of the stomach.

3. Pepsin converts proteins into proteoses and peptones (peptides).

4. The mucus and bicarbonates play an important role in lubrication and protection of the mucosal epithelium from concentrated hydrochloric acid- pH (pH 1.8).

Special type of proteolytic enzyme in infants:
Rennin is a proteolytic enzyme found in gastric juice of infants which helps in the digestion of milk proteins. The bile, pancreatic juice and the intestinal juice are the secretions released into the, small intestine.

Pancreatic juice:
It contains inactive enzymes

Trypsinogen is activated by an enzyme, enterokinase, secreted by the intestinal mucosa into aqtive trypsin.

Contents of Bile and functions:
The bile released into the duodenum contains bile pigments (bilirubin and bili-verdin), bile salts, cholesterol and phospholipids but no enzymes Bile helps in emulsification of fats, i.e., breaking down of the fats into very smalfmicelles.

Bile also activates lipases. The intestinal mucosal epithelium has goblet cells which secrete mucus. The secretions of the brush border cells of the mucosa alongwith the mucus constitute the intestinal juice or succu sentericus.

Intestinal juice/succus entericus:
It contains enzymes like

1. disaccharidases (eg: maltase)
2. dipeptidases
3. lipases,
4. nucleosidases etc.

How does the intestine protect itself from digestion?
1. The mucus alongwith the bicarbonates from the pancreas protects the intestinal mucosa from acid as well as provide an alkaline medium (pH 7.8) for enzymatic activities.

2. Sub-mucosal glands (Brunner’s glands) also help in this.

The breakdown of biomacromolecules occurs in the duodenum region of the small intestine. The simple substances thus formed are absorbed in the jejunum and ileum regions of the small intestine. The undigested and unabsorbed substances are passed on to the large intestine.

Functions of large intestine:

1. Absorption of some water, minerals and certain drugs
2. Secretion of mucus which helps in adhering the waste (undigested) particles together and lubricating it for an easy passage.

The undigested, unabsorbed substances called faeces enters into the caecum of the large intestine through ileo-caecal valve, which prevents the back flow of the faecal matter. It is temporarily stored in the rectum till defaecation.

• The sight, smell and the presence of food in the oral cavity can stimulate the secretion of saliva.
• Gastric and intestinal secretions are also stimulated by neural signals.
• The muscular activities of different parts of the alimentary canal controlled by neural mechanisms, both local and through CNS.

ABSORPTION OF DIGESTED PRODUCTS:

1. The end products of digestion passthrough the intestinal mucosa into the blood or lymph.
2. It is carried out by passive, active or facilitated transport mechanisms.
3. Small amounts of monosacharides like glucose, amino acids and some of electrolytes like chloride ions are generally absorbed by simple diffusion.
4. Fructose and some amino acids are absorbed with the help of the carrier ions like Na⁺. This mechanism is called the facilitated transport.
5. Transport of water depends upon the osmotic gradient.
6. Various nutrients like amino acids, monosacharides like glucose,electrolytes like Na⁺ are absorbed into the blood by active transport and hence requires energy.

How does fat absorption occur?
Fatty acids and glycerol being insoluble, cannot be absorbed into the blood. They are first incorporated into small droplets called micelles which move into the intestinal mucosa. Then, the fat globules are coated with small protein called as chylomicrons which are transported into the lymph vessels (lacteals) in the villi.

These lymph vessels ultimately release the absorbed substances into the blood stream. The maximum absorption occurs in the small intestine. The absorbed substances finally reach the tissues which utilise them for their activities. This process is called assimilation.

The digestive wastes, solidified into faeces in the rectum initiate a neural reflex causing an urge for its removal. The egestion of faeces to the outside through the anal opening (defaecation) is a voluntary process and is carried out by a mass peristaltic movement.

DISORDERS OF DIGESTIVE SYSTEM:
Jaundice:
The liver is affected, skin and eyes turn yellow due to the deposit of bile pigments.

Vomiting:
It is the ejection of stomach contents through the mouth. This reflex action is controlled by the vomit centre in the medulla. „

Diarrhoea:
The abnormal frequency of bowel movement and increased liquidity of the faecal discharge is known as diarrhoea. It reduces the absorption of food.

Constipation:
In constipation, the faeces are retained within the rectum as the bowel movements occur irregularly. ‘

Indigestion:
In this condition, the food is not properly digested leading to a feeling of fullness. The causes are inadequate enzyme secretion, anxiety, food poisoning, overeating, and spicy food.

NCERT SUPPLEMENTARY SYLLABUS
Calorific value of carbohydrate, protein and fat:
Carbohydrates, proteins and fats are chief sources of energy in humans. These are oxidized and released energy stored in ATP, it is used for many activities of the cell.

calorific value kcal = 4.184kJ):
It is defined as the amount of heat produced in calories (cal) or in joules (J) from complete combustion of 1 gram food in a bomb calorimeter (a closed metal chamber filled with 02). One kilocalorie is the amount of heat energy needed to raise the temperature of one kilogram of water through 100C(1.80F).

The calorific values of carbohydrates, proteins and fats are 4.1 kcal /g, 5.65 kcal /g and 9.45 kcal/g, respectively. The actual amounts of energy liberated in the body by these nutrients referred to as the physiologic value of the food, and are 4.0 kcal /g, 4.0 kcal Ig and 9.0 kcal /g respectively.

DEFICIENCY DISEASES:
The low amount of nutrients (Vitamin A, iron and iodine) in the diet cause deficiency disorders The important among them is protein energy malnutrition (PEM). lt is major health and nutritional problems in India.

Young children (0-6 years) require more protein for each kilogram of body weight than adults. So they are more vulnerable to malnutrition. Malnutrition leads to permanent impairment of physical and mental growth and childhood mortality and morbidity. The details of the disorders are given below.

The child suffering from PEM can recover if adequate quantities of protein and carbohydrate rich food are given.

Students can Download Chapter 3 Structural Organisation in Animals Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 3 Structural Organisation in Animals

What is a tissue?
In multicellular animals, a group of similar cells along with intercellular substances perform a specific function. Such an organization is called tissue.

ANIMAL TISSUES:
The tissues are different and are broadly classified into four types:

• Epithelial
• Connective
• Muscularand
• Neural.

Epithelial Tissue:
This tissues are found in the covering ora lining for some part of the body. The cells are compactly packed with little intercellular matrix.
There are two types of epithelial tissues namely:

1. SIMPLE EPITHELIUM
2. COMPOUND EPITHELIUM

1. Simple epithelium:

• Squamous
• Cuboidai
• Columnar

1. Squamous epithelium:
It forms single thin layer of flattened cells with irregular boundaries. They are found in the walls of blood vessels and air sacs of lungs and are involved in a functions like forming a diffusion boundary.

2. Cuboidai epithelium:
It is composed of a single layer of cube-like cells. This is commonly found in ducts of glands and tubular parts of nephrons in kidneys. Its main functions are secretion and absorption.

3. Columnar epithelium:
It is composed of a single layer of tall and slende cells. Their nuclei are located at the base. Free surface may have microvilli. They are found in the lining of stomach and intestine and help in secretion and absorption.

Ciliated epithelium:
If the columnar or cuboidai cells bear cilia on their free surface they are called ciliated epithelium Their function is to move particles or mucus in a specific direction overthe epithelium. They are present in bronchioles and fallopian tubes.

Glandular epithelium:
The modified columnar or cuboidal cells perform secretion and are called glandular epithelium.
They are mainly of two types:

• Unicellular (goblet cells of the alimentary canal)
• Multicellular(salivary gland).

On the basis of the mode of pouring of their secretions, glands are divided into two categories namely exocrine and endocrine glands.
Exocrine glands:
They secrete mucus, saliva, earwax, oil, milk, digestive enzymes and other cell products. These products are released through ducts or tubes.

Endocrine glands:
They do not have ducts. Their products called hormones are secreted directly into the blood.

2. Compound epithelium:
It is multi-layered of cells.
a. Their main function is to provide protection against chemical and mechanical stresses.

b. They cover the dry surface of the skin, the moist surface of buccal cavity, pharynx, inner lining of ducts of salivary glands and of pancreatic ducts.

Three types of cell junctions are found in the epithelium and other tissues. These are called as tight, adhering and gap junctions.

1. Tight junctions help to stop substances from leaking across a tissue.
2. Adhering junctions perform cementing to keep neighbouring cells together.
3. Gap junctions facilitate the cells to communicate with each other by connecting the cytoplasm of adjoining cells for rapid transfer of ions and molecules.

Connective Tissue:
Connective tissues helps to linking and supporting othertissues/organs of the body. They include

• cartilage
• bone
• adipose
• blood.

Collagen or elastin:
In all connective tissues except blood, the cells secrete fibres of structural proteins called collagen or elastin.
The fibres provide strength, elasticity and flexibility to the tissue.
These cells also secrete modified polysaccharides, which accumulate between cells and fibres and act as matrix (ground substance).
Connective tissues are classified into three types:

• Loose connective tissue
• Dense connective tissue and
• Specialised connective tissue

Loose connective tissue:
They are loosely arranged in a semi-fluid ground substance. For example,
Areolar tissue:
It is present beneath the skin. It contains fibroblasts (cells that produce and secrete fibres),macrophages and mast cells.

Adipose tissue:
It is the loose connective tissue located mainly beneath the skin. The cells of this tissue are specialised to store fats.

Dense connective tissues.
In this Fibres and fibroblasts are compactly packed and are called dense regular and dense irregular tissues. In the dense regular connective tissues, the collagen fibres are present injows between bundles of fibres.
eg:

• Tendons, which attach skeletal muscles to bones
• ligaments which attach one bone to another.

Dense irregular connective tissue has fibroblasts and many fibres (mostly collagen) that are present in the skin.

Specialized connective tissues: They are Cartilage, bones and blood.

Cartilage:
Cells of this tissue (chondrocytes) are enclosed in small cavities within the matrix. Most of the cartilages in vertebrate embryos are replaced by bones in adults. Cartilage is present in the tip of nose, outer ear joints, between adjacent bones of the vertebral column, limbs and hands in adults.

Bones:
They have a hard ground substance rich in calcium salts and collagen fibres which give bone its strength. Bones support and protect softer tissues and organs. The bone cells (osteocytes) are present in the spaces called lacunae.

Limb bones, such as the long bones of the legs, serve weight-bearing functions. They also interact with skeletal muscles attached to them to bring about movements. The bone marrow in some bones is the site of production of blood cells.

Blood:
It is a fluid connective tissue containing plasma, red blood cells (RBC), white blood cells (WBC) and platelets. It also helps in the transport of various substances.

Muscle Tissue:
It consists of long, cylindrical fibres arranged in parallel arrays. These fibres are composed of numerous fine fibrils, called myofibrils. Muscle fibres contract (shorten) in response to stimulation, then relax (lengthen) and in their uncontracted state. Muscles play an active role in all the movements of the body Muscles are of three types, skeletal, smooth, and cardiac.
1. Skeletal muscle:
It is the tissue is closely attached to skeletal bones. In a typical muscle such as the biceps, striated (striped) skeletal muscle fibres are bundled together in a parallel fashion.

2. Smooth muscle:
These fibres taper at both ends (fusiform) and do not show striations. The wall of internal organs such as the blood vessels, stomach and intestine contains this type of muscle tissue. Smooth muscles are ‘involuntary’ as their functioning cannot be directly controlled.

3. Cardiac muscle tissue:
It is a contractile tissue present only in the heart. Cell junctions fuse the plasma membranes of cardiac muscle cells and make them stick together In Communication when one cell receives a signal to contract, its neighbours are also stimulated to contract.

Neural Tissue:
Neurons, the unit of neural system are excitable cells The neuroglial cell which constitute the rest of the neural system protect and support neurons. Neuroglia make up more than one half the volume of neural tissue in our body.

Nerve impulse transmisssion:
When a neuron is suitably stimulated, an electrical disturbance is generated which swiftly travels along its plasma membrane and reaches at the neuron’s endings, or output zone, triggers events that may cause stimulation or inhibition of adjacent neurons and other cells.

ORGAN AND ORGAN SYSTEM:
Each organ in our body is made of one or more type of tissues. For example, our heart consists of all the four types of tissues, i.e., epithelial, connective, muscular and neural. In animals morphology refers to the external appearance of the organs or parts of the body.

EARTHWORM:
Earthworm is a reddish brown terrestrial invertebrate The common Indian earthworms are Pheretima and Lumbricus.

Morphology:
They have long cylindrical body.lt is divided into more than hundred short segments which are similar. The dorsal surface of the body is marked by a dark median mid dorsal line (dorsal blood vessel). The ventral surface is distinguished by the presence of genital openings (pores).

Anterior end consists of the mouth and the prostomium, a lobe which serves as a covering for the mouth . The prostomium is sensory in function. The first body segment is called the peristomium (buccal segment) which conjoins the mouth.

In a mature worm, segments 14-16 are covered by a prominent dark band of glandular tissue called clitellum. Thus the body is divisible into three prominent regions.

• preclitellar
• clitellar &
• postclitellar segments

Four pairs of spermathecal apertures are situated 5^th – 9^th segments. A single female genital pore is present in the mid-ventral line of 14^th segment. A pair of male genital pores are present on 18th segment.

Numerous minute pores called nephridiopores open on the surface of the body. In each body segment, except the first, last and clitellum, there are rows of S-shaped setae, Setae plays an important role is in locomotion.

Anatomy:
The body wall of the earthworm is covered externally by a thin non-cellular cuticle below which is the epidermis, two muscle layers and an innermost coelomic epithelium. The epidermis is made up of a single layer of columnar epithelial cells which contain secretory gland cells. A terminal mouth opens into the

1. buccal cavity (1 – 3 segments) which leads into muscular pharynx.
2. Oesophagus (5 – 7 segments), continues into a muscular gizzard (8 – 9 segments).

It helps in grinding the soil particles and decaying leaves etc. The stomach extends from 9 – 14 segments. The food of the earthworm is decaying leaves and organic matter mixed with soil. Calciferous glands, present in the stomach, neutralise the humic acid present in humus.

Intestine starts from the 15^th segment onwards and continues till the last segment. A pair of short and conical intestinal caecae project from the intestine on the 26^th segment. The characteristic feature of the intestine between 26 – 35 segments is the presence of internal median fold of dorsal wall called typhlosole.

This increases theeffective area of absorption in the intestine. The alimentary canal opens to the exterior by a small rounded aperture called anus. These simpler molecules are absorbed through intestinal membranes and are utilised. Pheretima shows closed type of blood vascular system, consisting of blood vessels, capillaries and heart.

Blood glands are present on the 4^th, 5^th and 6^th segments. They produce blood cells and haemoglobin which is dissolved in blood plasma. Blood cells are phagocytic in nature.

In Earthworms respiratory exchange occurs through moist body surface into their blood stream. The excretory organs occur as segmentally arranged coiled tubules called nephridia They are of three types:

• septal nephridia, present on both the sides of intersegmental septa of segment 15 to the last that open into intestine,
• integumentary nephridia, attached to lining of the body wall of segment 3 to the last that open on the body surface and
• pharyngeal nephridia, present as three paired tufts in the 4^th, 5^th and 6^th segments

Nephridia:
It regulate the volume and composition of the body fluids. A nephridium starts out as a funnel that collects excess fluid from coelomic chamber. The funnel connects with a tubular part of the nephridium which delivers the wastes.

Nervous system:
It is represented by ganglia arranged segment wise on the ventral paired nerve cord (3^rd and 4^th segments). The cerebral ganglia along with other nerves in the ring integrate sensory input as well as command muscular responses of the body.

Sensory system does not have eyes but does possess light and touch sensitive organs to distinguish the light intensities and to fee the vibrations in the ground. Worms have specialised chemoreceptors (taste receptors) which react to chemical stimuli. Earthworm is hermaphrodite (bisexual), i.e., testes and ovaries are present in the same individual.

There are two pairs of testes present in the 10^th and 11^th segments. Their vasa deferentia run up to the 18^th segment where they join the prostatic duct. Two pairs of accessory glands are present one pair each in the 17^th and 19^th segments. The common prostrate and spermatic duct opens to the exterior by a pair of male genital pores on the ventro-lateral side of the 18^th segment.

Four pairs of spermathecae are located in 6^th – 9^th segments (one pair in each segment).They receive and store spermatozoa during copulation. One pair of ovaries is attached at the 12^th and 13^th segments. Ovarian funnels are present beneath the ovaries which continue into oviduct, join together and open on the ventral side as a single median female genital pore on the 14^th segment.

A mutual exchange of sperm occurs between two worms during mating. Mature sperm and egg cells and nutritive fluid are deposited in cocoons produced by the gland cells of clitellum.

Fertilisation:
Fertilisation and development occur within the cocoons which are deposited in soil. The ova (eggs) are fertilised by the sperm cells within the cocoon. The cocoon holds the worm embryos. After about 3 weeks, each cocoon produces two to twenty baby worms. Earthworms development is direct, i.e., there is no larva formed.

Earthworms are known as ‘friends of farmers’ because they make burrows in the soil and make it porous which helps in respiration and penetration of the developing plant roots. The process of increasing fertility of soil by the earthworms is called vermicomposting. They are also used as bait in game fishing

COCKROACH:
Cockroaches are are included in class Insecta of Phylum Arthropoda. They are nocturnal omnivores that live in damp places throughout the world. They are found in human homes and thus are serious pests and vectors of several diseases.

Morphology:
The adults of the common species of cockroach, Periplaneta americana are about 34 – 53 mm long with wings that extend beyond the tip of the abdomen in males. The body of the cockroach is segmented and divisible into three distinct regions – head, thorax and abdomen. The body is covered by a hard chitinous exoskeleton.

Exoskeleton has hardened plates called sclerites that are joined to each other by a thin and flexible articular membrane (arthrodial membrane). Head is formed by the fusion of six segments and shows great mobility in all directions due to flexible neck It has compound eyes. A pair of antennae arise from sockets lying in front of eyes. They help in monitoring the environment.

Anterior end of the head bears appendages forming biting and chewing type of mouth parts. It consists of a labrum (upper lip), pair of mandibles, a pair of maxillae and a labium (lower lip). A median flexible lobe, acting as tongue (hypopharynx), lies within the cavity enclosed by the outhparts.
Thorax consists of three parts:

1. prothorax
2. mesothorax
3. metathorax.

Each thoracic segment bears a pair of walking legs. The first pair of wings arises from mesothorax and the second pair from metathorax. Forewings (mesothoracic) called tegmina are opaque dark and leathery and cover the hind wings when at rest. The hind wings are transparent, membranous and are used in flight.

The abdomen in both males and females consists of 10 segments. In females, the 7^th sternum is boat shaped and together with the 8^th and 9^th sterna forms a genital pouch whose anterior part contains female gonopore, spermathecal pores and collateral glands.

In males, genital pouch lies at the hind end of abdomen bounded dorsally by 9^th and 10^th terga and ventrally by the 9^th sternum. It contains dorsal anus, ventral male genital pore and gonapophysis. Males bear a pair of short, threadlike anal styles which are absent in females. In both sexes, the 10^th segment bears a pair of jointed filamentous structures called anal cerci.

Anatomy:
The alimentary canal is divided into three regions: foregut, midgut and hindgut The mouth opens into a short tubular pharynx, leading to a narrow tubular passage called oesophagus.

Oesophagus opens into a sac like structure called crop used for storing of food. The crop is followed by gizzard or proventriculus. Gizzard helps in grinding the food particles. A ring of 6 – 8 blind tubules called hepatic or gastric caecae is present at the junction of foregut and midgut, which secrete digestive juice.

At the junction of midgut and hindgut is present another ring of 100 – 150 yellow coloured thin filamentous Malphigian tubules. They help in removal of excretory products from haemolymph. The hindgut is differentiated into ileum, colon and rectum. The rectum opens out through anus.

Blood vascular system of cockroach is an open type Blood vessels are open into space (haemocoel). Visceral organs located in the haemocoel are bathed in blood (haemolymph).The haemolymph is composed of colourless plasma and haemocytes.

Heart of cockroach consists of elongated muscular tube lying along mid dorsal line of thorax and abdomen. Blood from sinuses enter heart through ostia and is pumped anteriorly to sinuses again. The respiratory system consists of a network of trachea, that open through 10 pairs of small holes called spiracles present on the lateral side of the body.

Thin branching tubes carry oxygen from the airto all the parts. Exchange of gases take place at the tracheoles by diffusion. During excretion Malpighian tubules absorb nitrogenous waste products and convert them into uric acid which is excreted out through the hindgut. Therefore, this insect is called uricotelic.

In addition, the fat body, nephrocytes and urecose glands also help in excretion. The nervous system of cockroach consists of segmentally arranged ganglia joined by paired longitudinal connectives. Three ganglia lie in the thorax, and six in the abdomen.


The nervous system of cockroach is spread throughout the body. If the head of a cockroach is cut off, it will still live for as long as one week. In the head region, the brain is represented by supra-oesophageal ganglion which supplies nerves to antennae and compound eyes. In cockroach, the sense organs are antennae, eyes, maxillary palps, larfial palps, anal cerci, etc.

Compound eves of cockroach:
The compound eyes are situated at the dorsal surface of the head. Each eye consists of about 2000 hexagonal ommatidia. With the help of several ommatidia, a cockroach can receive several images of an object. This kind of vision is known as mosaic vision with more sensitivity but less resolution, being common during night (hence called nocturnal vision).

Cockroaches are dioecious Male reproductive system consists of a pair of testes lying one on each lateral side in the 4^th – 6^th abdominal segments. From each testis arises a thin vas deferens, which opens into ejaculatory duct through seminal vesicle. The ejaculatory duct opens into male gonopore situated ventral to anus.

A characteristic mushroom shaped gland is present in the 6^th – 7^th abdominal segments which functions as an accessory reproductive gland. The external genitalia are represented by male gonapophysis or phallomere The sperms are stored in the seminal vesicles and are glued together in the form of bundles called spermatophores which are discharged during copulation.

The female reproductive sysytem consists of two large ovaries, lying laterally in the 2^nd – 6^th abdominal segments. Each ovary is formed of a group of eight ovarian tubules or ovarioles, containing a chain of developing ova. Oviducts of each ovary unite into a single median oviduct (also called vagina) which opens into the genital chamber.

Sperms are transferred through spermatophores. Their fertilised eggs are stored in capsules called oothecae. On an average, females produce 9 – 10 oothecae, each containing 14 – 16 eggs. The development of P. Americana is paurometabolous, meaning there is development through nymphal stage.

The nymph grows by moulting about 13 times to reach the adult form. The next to last nymphal stage haswing pads but only adult cockroaches have wings.

FROGS:
Frogs are belong to class Amphibia of phylum Chordata. The most common species of frog found in India is Rana tigrina. Their body temperature varies with the temperature of the environment. Such animals are called cold blooded or poikilotherms They have the ability to change the colour to hide them from their enemies (camouflage).

This protective coloration is called mimicry. During peak summer and winterthey take shelter in deep burrows to protect them from extreme heat and cold. This is called as summer sleep (aestivation) and wintersleep (hibernation).

Morphology:
The skin is maintained in a moist condition. The frog never drinks water but absorb it through the skin. Body of a frog is divisible into head and trunk. A neck and tail are absent. Above the mouth, a pair of nostrils is present. Eyes are bulged and covered by a nictitating membrane that protects them while in water.

On either side of eyes a membranous tympanum (ear) receives sound signals. The forelimbs and hind limbs help in swimming, walking, leaping and burrowing. The hind limbs end in five digits and they are larger and muscular than fore limbs that end in four digits.

Feet have webbed digits that help in swimming. Frogs exhibit sexual dimorphism. Male frogs can be distinguished by the presence of sound producing vocal sacs and also a copulatory pad on the first digit of the fore limbs which are absent in female frogs.

Anatomy:
The body cavity consists of organ systems such as digestive, circulatory, respiratory, nervous, excretory and reproductive systems. The digestive system consists of alimentary canal and digestive glands. The alimentary canal is short because frogs are carnivores and hence the length of intestine is reduced.

The mouth opens into the buccal cavity that leads to the oesophagus through pharynx. Oesophagus is a short tube that opens into the stomach which in turn continues as the intestine,rectum and finally opens outside by the cloaca. Liver secretes bile that is stored in the gall bladder. Pancreas, a digestive gland produces pancreatic juice containing digestive enzymes.

Digestion of food takes place by the action of HCI and gastric juices secreted from the walls of the stomach. Partiailv digested food called chyme is passed from stomach to the first part of the intestine, the duodenum. The duodenum receives bile from gall bladder and pancreaticjuicesfrom the pancreas through a common bile duct.

Bile emulsifies fat and pancreatic juices digest carbohydrates and proteins. Final digestion takes place in the intestine. Digested food is absorbed by the numerous finger-like folds in the inner wall of intestine called villi and microvilli. The undigested solid waste moves into the rectum and passes out through cloaca.

In water, skin acts as aquatic respiratory organ (cutaneous respiration). Dissolved oxygen in the water is exchanged through the skin by diffusion. On land, the buccal cavity, skin and lungs act as the respiratory organs. The respiration by lungs is called pulmonary respiration.

The lungs are a pair of elongated, pink coloured sac- like structures present in the upper part of the trunk region (thorax). Air enters through the nostrils into the buccal cavity and then to lungs. During aestivation and hibernation gaseous exchange takes place through skin. The blood vascular system involves heart, blood vessels and blood.

The lymphatic system consists of lymph, lymph channels and lymph nodes. Heart is a muscular structure situated in the upper part of the body cavity. It has three chambers, two atria and one ventricle and is covered by a membrane called pericardium. Atriangularstructure called sinus venosus joins the right atrium.

It receives blood through the major veins called vena cava. The ventricle opens into a saclike conus arteriosus on the ventral side of the heart. The blood from the heart is carried to all parts of the body by the arteries (arterial system).The veins collect blood from different parts of body to the heart and form the venous system.

Special venous connection between liver and intestine as well as the kidney and lower parts of the body are present in frogs. The former is called hepatic portal system and the latter is called renal portal system.

The blood is composed of plasma and cells. The blood cells are RBC (red blood cells) or erythrocytes, WBC (white blood cells) or leucocytes and platelets. RBC’s are nucleated and contain red coloured pigment namely haemoglobin. The lymph is different from blood. It lacks few proteins and RBCs.

The excretory system consists of a pair of kidneys, ureters, cloaca and urinary bladder. Each kidney is composed of several structural and functional units called uriniferous tubules or nephrons. Two ureters emerge from the kidneys in the male frogs. The ureters act as urinogenital duct which opens into the cloaca.

In females the ureters and oviduct open seperately in the cloaca. The thin-walled urinary bladder is present ventral to the rectum which also opens in the cloaca. The frog excretes urea and thus is a ureotelic animal.

The chemical coordination of various organs of the body is achieved by hormones which are secreted by the endocrine glands. The endocrine glands found in frog are pituitary, thyroid, parathyroid, thymus, pineal body, pancreatic islets, adrenals and gonads.

The nervous system is organized into a central nervous system (brain and spinal cord), a peripheral nervous system (cranial and spinal nerves) and an autonomic nervous system (sympathetic and parasympathetic). There are ten pairs of cranial nerves arising from the brain. Brain is enclosed in a bony structure called brain box(cranium).

The brain is divided into fore-brain, mid-brain and hind-brain. Forebrain includes olfactory lobes, paired cerebral hemispheres and unpaired diencephalon. The midbrain is characterised by a pair of optic lobes. Hind-brain consists of cerebellum and medulla oblongata.

The medulla oblongata passes out through the foramen magnum and continues into spinal cord, which is enclosed in the vertebral column. Frog has different types of sense organs, namely organs of touch (sensory papillae), taste (taste buds), smell (nasal epithelium), vision (eyes) and hearing (tympanum with internal ears).

Eyes in a frog are a pair of spherical structures situated in the orbit in skull. External ear is absent in frogs and only tympanum can be seen externally. The ear is an organ of hearing as well as balancing (equilibrium).

Male reproductive organs consist of a pair of yellowish ovoid testes which are found adhered to the upper part of kidneys by a double fold of peritoneum called mesorchium. Vasa efferentia are 10 – 12 in number that arise from testes. They enter the kidneys on their side and open into Bidder’s canal.

Finally it communicates with the urinogenital duct that comes out of the kidneys and opens into the cloaca. The cloaca is a small, median chamber that is used to pass faecal matter, urine and sperms to the exterior.

The female reproductive organs include a pair of ovaries. They are situated near kidneys and there is no functional connection with kidneys. A pair of oviduct arising from the ovaries opens into the cloaca separately. A mature female can lay 2500 to 3000 ova at a time.

Fertilisation is external and takes place in Water. Development involves a larval stage called tadpole. Tadpole undergoes metamorphosis to form the adult. Frogs are beneficial for mankind because they eat insects and protect the crop.

Frogs maintain ecological balance because these serve as an important link of food chain and foodweb in the ecosystem. In some countries the muscular legs of frog are used as food by man.

Students can Download Chapter 12 Thermodynamics Notes, Plus One Physics Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Physics Notes Chapter 12 Thermodynamics

Summary
Thermo dynamics is the branch of Physics that deals with concept of heat and temperature, their inter-conversions and other forms of energy. In thermo dynamics state of system is specified by macroscopic variables such as pressure, temperature, volume, mass, composition… etc.

Thermo Equilibrium
Thermo dynamic equilibrium:
A system is said to be in thermodynamic equilibrium if the macroscopic variables used to describe the system does not change with time.
Eg: Agas enclosed in a rigid container (characterized by P, V, T, m, and composition) The equilibrium of a thermodynamic system depends on surroundings and nature of wall that separates the system from surroundings. The wall can be

• Adiabatic wall – It does not allow flow of heat (energy).
• Diathermic wall – It allows the flow of heat (so that it can comes to thermal equilibrium).

Zeroth Law Of Thermodynamics
Zeroth law of thermodynamics gives concept of temperature. R.H Fowler formulated this law in 1931. According to Zeroth law of thermodynamics, the systems in thermal equilibrium with a third system separately are in thermal equilibrium with each other.

Let A & B are in thermal equilibrium with each other. If they are separately in thermal equilibrium with C, then the three systems are in thermal equilibrium
(T_A = T_B = T_C).

Heat, Internal Energy And Work
Internal Energy (U):
internal energy of a gas is the sum of potential energy and kinetic energy (translational kinetic energy, rotational kinetic energy and vibrational energy) Internal energy is a thermodynamic variable and hence it depends on state of the thermodynamic system.

Heat and Work:
The internal energy of a system can be changed either by heat or by work. Heat is energy transfer between a system and surroundings due to temperature difference. Work is mode of energy transfer brought about by means like moving piston (it is not due to temperature difference)

First Law Of Thermodynamics
According to first law of thermodynamics, heat supplied to a system is used to increase its internal energy and to do work.
If ∆Q is heat supplied to the system, ∆W is work done by the system and Au is change in internal energy, then ∆Q = ∆U + AW
Note:

• If the entire heat supplied to the system is used to do work, then ∆Q = ∆W
• The work done against constant pressure, ∆W = P∆V, ∆Q = ∆U + P∆V.

Specific Heat Capacity
Molar specific heat capacity of solid:
Consider a solid consisting of N atoms. Each atom have an average energy 3K_BT, where K_B is Botlzman constant. Total energy for one,mole
U = 3K_BT × N_A
N_A is avagadro number.
At constant pressure, ∆Q = ∆U + P∆V
For solid ∆V is negligible ∆Q = ∆U
Molar specific heat capacity

Thus molar specific heat capacity of solids is found to be 3R. But at low temperature molar specific heat capacity is not a constant.
Specific heat capacity of water:
The specific heat capacity of water is 4186 J Kg-‘K1. But the specific heat capacity of water changes with temperature as shown.

Mayor’s Relation; C_p – C_v = R
If molar specific heat capacity of constant pressure is C_p and that at constant volume is C_v then C_p – C_v = R, for an ideal gas.
Proof:
According to 1^st law of thermodynamics
∆Q = ∆U + P∆V
If ∆Q heat is absorbed at constant volume (∆V = 0)

From ideal gas equation for one mole PV = RT Differentiating w.r.t. temperature (at constant pressure)

Substituting in equation (2)

Equation (4) – Equation (1), we get C_p – C_v = R.

Thermodynamic State Variable And Equation Of State
Extensive and Intensive variables:
Thermodynamic variables can be extensive or intensive. Extensive variables depend on size of the system.
Eg: mass, internal energy, volume.
Intensive variables are independent of size of system.
Eg: Pressure, temperature, density.
Equation of state:
The relation between state variables of a system is called equation of state. For an ideal gas equation of state is PV = µRT

Thermodynamic process
1. Quasi-static process:
The thermodynamic process in which thermo dynamic variables (P, V, T… etc) changes so slowly that the system remains in thermal and mechanical equilibrium is called quasi static (nearly static) process. In quasi-static process change in temperature or pressure will be infinitesimally small. The different types of quasi static process are listed in the above table.

2. Work done in isothermal process:
For an isothermal process, the equation of state is
PV = constant = µRT
P = \(\frac{\mu \mathrm{RT}}{\mathrm{V}}\)
Let a system undergoes an isothermal process at temperature T, from the state (P₁, V₁) to (P₂, V₂). Let ‘DV’ be a small charge in volume due to pressure P.
Then work done (for ∆V)
∆W = P∆V

3. Work done by adiabatic process:
Let an ideal gas undergoes adiabatic charge from (P₁, V₁) to (P₂, V₂). The equation for adiabatic charge is PV^γ = constant = k

from equation (a) P₁V₁^γ = P₂V₂^γ = k

Substituting ideal gas equation.

Note:

1. The graph connecting P and V of isothermal process is called isotherm.
2. In adiabatic process
   • T₁ < T₂, then work is done on gas (w < 0)
   • T₁ > T₂, then work is done by gas (w > 0)
3. For Isothermal process
   • V₁ < V₂, w > 0 work is done by gas
   • V₁ > V₂, w < 0 work is done on gas.
4. In isochoric process no work is done on or by gas because volume is constant.

Cyclic process:
In cyclic process, the system returns to its initial state such that change in internal energy is zero. The P – V diagram for cyclic process will be closed loop and area of this loop gives work done or heat absorbed by system.

Heat Engines
Heat engines converts heat energy into mechanical energy. Heat engine is a device by which a system is made to undergo a cyclic process that results in conversion of heat to work.
Heat engines consists of:

1. Working substance (the system which undergoes cyclic process) eg: mixture of fuel vapor and air in diesel engine, steam in steam engine.
2. An external reservoir at a high temperature (T₁) – it is the source of heat.
3. An external reservoir at low temperature (T₂) or sink

Working:
The working substances absorbs an energy Q₁ from source reservoir at a temperature T₁. It undergoes cyclic process and releases heat Q₂ to cold reservoir. The change in heat (Q₁ – Q₂) is converted in to work (mechanical energy).
Efficiency of heat engine (η):
The efficiency of heat engine is the ratio of work done to input heat.

Note:

• Q₂ = 0, η = 1. When entire heat input is converted into work heat engine is 100% efficient. But practically 100% efficiency cannot be achieved. It is limited by second law of thermodynamics.
• Heat engine can be external combustion engine or internal combustion engine.

In external combustion engine, the fuel (system) is heated by external furnace.
Eg.: Steam engine.
In internal combustion engine, fuel is heated internally by exothermic chemical reactions.
Eg: Diesel engine, Patrol engine.

Refrigerators And Heat Pumps
Refrigerator is reverse of heat engine, the device used to cool a portion of space (inside a chamber) is refrigerator. The device used to pump heat into a portion of space (to warm-up room) is called heat pump.

In both devices, the working substance absorbs heat Q₂ from cold reservoir at temperature T₂. Some external work (by compression of gas by electric means) is done on it and heat Q₁ is supplied to hot reservoir at T₁.

The working cycle of refrigerator:
In refrigerator the working substance is a gas (freon)

Step1: The gaseous working substance is converted into vapor- liquid mixture at lower temperature (T₂)
Step 2: The cold fluid absorbs heat from region to be cooled (cold reservoir) and convert it into vapor.
Step 3: The vapor is heated by external work.
Step 4: The vapor release heat to surroundings and then comes to initial temperature T₂.

The coefficient of performance (α):
The coefficient of performance of refrigerator is defined as
α = \(\frac{Q_{2}}{W}\)
where Q₂ is heat extracted from cold reservoir and W is work done on system.
Note:

• The working substance in refrigerator is termed as refrigerant.
• For heat engine η can not exceed 1. But α can be greater than one.

Second law of Thermo dynamics
Kelvin – Plank statement:
No process is possible whose sole result is the absorption of heat from a reservoir and complete conversion of heat into work.
Clausius statement:
No process is possible whose sole result is the transfer of heat from a colder object to hotter object.

Reversible And Irreversible Processes
A themodynamic process is said to be reversible if the process can bring both system and surrounding back to the original state without any change.

A reversible thermodynamic process is ideal case. Most thermodynamic processes are irreversible because the process involves dissipative effects like friction, viscous force etc. and during such process, system passes through non-equilibrium states.
Note: Condition for a thermodynamic process to be reversible is

1. Quasi static
2. non-dissipative

Question 1.
What is the importance of reversibility in thermo dynamics?
Answer:
The main concern of thermodynamics is efficiency with which heat can be converted into work. According to second law of thermodynamics, the efficiency can not be 100%. The heat engine can have highest efficiency only if the cyclic process is reversible.

Carnot’S Engine
Carnot’s theorem:
Sadi carnot proposed Carnot’s theorem. According to Carnot’s theorem

1. No engine operating between two temperature can have efficiency more than that of Carnot’s engine,
2. The efficiency of Carnot’s engine is independent of nature of working substance.

Carnot’s engine:
A reversible heat engine operating between two temperatures is called Carnot’s engine.
Carnot’s cycle:
The Carnot cycle consists of two isothermal processes and two adiabatic processes.

The cylindar is placed on the source. The gas expands and temperature increases. This is the first stroke of the heat engine. The expansion is an isothermal expansion.

During this expansion the working substance originally at the state A (P₁, V₁, T₁) has new variable (P₂, V₂, T₁). The variation A to B is shown byAB in v-p graph.

During the second stroke, the cylinder is placed on the stand and the gas is allowed to expand further and reaches the state C. The new Co-ordinate are (P₃, V₃, T₂).

This expansion is adiabatic expansion. The third stroke is carried out when cylinder is placed on the zink. The cylinder undergoes for isothermal compression and coordinate becomes (P₄, V₄, T₂).

In the fourth and final stroke, the cylinder is placed on the non conducting stand. The gas is compressed back to state A. This is adiabatic compression.

1. The work done by gas in one Carnot cycle
Step 1: Isothermal expansion : The gas absorbs heat Q, from hot reserviorand undergoes Isothermal expansion.
[(P₁, V₁, T₁) → (P₂, V₂, T₂)]

Step 2: Adiabatic expansion
[(P₂, V₂, T₁) → (P₃, V₃, T₂)]

Step 3: Isothermal compression: The gas releases heat Q₂ to cold reservoir at T₂.
[(P₃, V₃, T₂) → (P₄, V₄, T₂)]

Step 4: Adiabatic compression
[(P₄, V₄, T₂) → (P₁, V₁, T₁)]

2. Efficiency of Carnot’s engine:

In adiabatic expansion from
(P₂, V₂, T₁) to (P₃, V₃, T₂)

In adiabatic compression
(P₄, V₄, T₂) to (P₁, V₁, T₁)

Thus equation (b) becomes η = 1 – \(\frac{T_{2}}{T_{1}}\) ……..(3)
Comparing this with equation (a)

Note:

• The equation
• Shows that efficiency of heat engine is independent of nature of working substance.

Students can Download Chapter 11 Thermal Properties of Matter Notes, Plus One Physics Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Physics Notes Chapter 11 Thermal Properties of Matter

Summary
Temperature And Heat
Temperature is a measure of hotness of a body. Heat is a form of energy transferred between two system (or system and surrounding) by virtue of temperature difference. The SI unit of heat is Joule (J) and that of tempera-ture is Kelvin (K).

Measurement Of Temperature
The instrument used to measure temperature is thermometer. The different temperature scales are Kelvin scale, Degree Celsius scale, and Fahrenheit scale. If t₁ and t_c are temperature in Fahrenheit scale and Celsius scale, then their linear relationship is given by

This relation can be graphically represented as shown

If T is temperature in kelvin scale, then
T = t_c + 273.15.
A comparison of the three temperature scales is shown

Ideal Gas Equation & Absolute Temperature Boyle’s law:
At constant temperature, pressure is inversely proportional to volume.
p α \(\frac{1}{V}\)
PV = constant _______(1)
Charle’s law: At constant pressure, volume is directly proportional to temperature
v α T
\(\frac{V}{T}\) = constant ______(2)
Combining (1) and (2), we get PV
\(\frac{PV}{T}\) = constant T
This is called ideal gas law. Generally, the law can be expressed for any quantity of dilute gas as

µ is the number of moles in given gas and R is universal gas constant.
The value of R is 8.31 J mol^-1 k^-1.
Absolute Temperature:
The minimum value of temperature for ideal gas is – 273.15°C (OK). This temperature is called absolute zero. On kelvin scale -273.15°C is taken as zero point.
Note:
The absolute temperature for a gas can be obtained by extrapolating the pressure versus temperature graph as shown below.

Thermal Expansion
The change in temperature of a body may change its length, area or volume. The fractional change in dimension [ratio of change in dimension to original dimension] is proportional to change in temperature.

The corresponding proportionally constant is called coefficient of thermal expansion or thermal expansivity. Thermal expansion can be defined as ratio of increase in dimension of body to increase in temperature.

There are different three types of thermal expansion, which are shown in the table given below
Note: (1)
Show that the coefficient of volume expansion for ideal gas is reciprocal of temperature
(α_v = 1/T)
Proof: Ideal Gas Equation is

At constant pressure P∆V = µR∆T ______(2).
Dividing we get

Anomalous behavior of water:
Generally volume of liquid increases with temperature .When water is heated, its volume starts to decrease from 0°C and reaches minimum at 4°C. Hence density of water is maximum at 4°C.

Question 1.
Derive the following relations

1. α_a = 2α_l
2. α_v = 3α_l

Answer:
Consider a cube of length ‘l’. Due to the increase in temperature ‘∆T’, length of cube increases by ∆l in all directions.
Coefficient of linear expansion, α_l = \(\frac{\Delta \ell}{\ell \Delta \mathrm{T}}\)
1. Increase in area of cube ∆A
= Final area – initial area
= (l + ∆l)² – l² = 2 × l × ∆l
[Neglecting ∆l²]
Area expansivity

Therefore, α_a = 2 . α_l.

2. Due to ‘∆T ’ the increase in volume of cube,
∆V = (l + + ∆l)³ – l³
= 3l²∆l²
[Neglecting ∆l² & ∆l³]

Therefore, α_v = 3 . α_l.

Specific Heat Capacity
Heat capacity:
Heat capacity (S) of substance is the quantity of heat required to increase the temperature of whole substance.
If ∆Q is the amount of heat required to increase the temperature by ∆T the heat capacity.

Specific heat capacity:
Specific heat capacity of a substance is defined as amount of heat required to increase temperature of unit mass of substance by one unit.
If ∆Q is amount of heat absorbed by substance of mass m and ∆T is change in temperature, then specific heat capacity is

The SI unit of specific heat capacity is J Kg^-1K^-1.
Molar specific heat capacity (C):
Molar specific heat capacity of a substance is the amount of heat required to increase the temperature of 1 mole of substance by one unit.
Its unit is J mol^-1 K^-1.
If a sample has ‘µ’ moles of substance, then its molar specific heat capacity is given by

Molar specific capacity are of two types:

• molar specific capacity at constant volume (CV)
• molar specific heat capacity at constant pressure (CP).

Note:

• Water has high specific heat capacity. So it is used as coolant in automobile radiators and as a heater in hot water bags.
• Due to high specific heat capacity of water, land is more warmer than water during daytime.

Calorimetry
Calorimetry means measurement of temperature. Calorimeter is a device used to measure heat. Calorimeter consists of a metallic vessel and a stirrer of same type. The vessel is kept inside a wooden jacket.

The wooden jacket contains insulating mate-rials like glass, wool etc. and hence it prevent heat loss. This jacket has a small opening at top and a thermometer is inserted into this hole.

Change Of State
A transition from one state (solid, liquid or gas) to another state is called change of state. There are four such transitions of state.

During change of state, the two different state coexist in thermal equilibrium and temperature remains constant until the completion of change of state.

Melting point:
The temperature at which solid and liquid coexist in thermal equilibrium with each other is called melting point. The melting point decreases with pressure

Boiling point.
The temperature at which liquid and vapour state of substance coexist in thermal equilibrium with each other is called boiling point. The boiling point increases with increase in pressure and it decreases with decrease in pressure.

Regelation

Take an ice block. Put a metal wire over the ice block and attach 5 kg. blocks at the two ends of wire as shown. Then we can see that the metal wire passes through the ice block to the other side without splitting it.

Explanation: The melting point of ice just below the wire decreases due to increase in pressure. As ice melts wire passes and refreeze (due to decrease in pressure). This process is called regelation.

Question 2.
Cooking is difficult at high altitude. Why?
Answer:
At high altitude, pressure is low. Boiling point decreases with decrease in pressure.

Question 3.
For cooking rice pressure cooker is preferred. Why?
Answer:
In pressure cooker, boiling point of water is increased by increasing pressure. Thus rice can be cooked at high temperature.

Question 4.
You might have observed the bubbles of steam coming from bottom of vessel when water is heated. These bubbles disappear as it reaches top of liquid just before boiling and they reach the surface at the time of boiling. Explain the reason?
Answer:
Just before boiling, the bottom of liquid will be warm and at the top, liquid will be cool. So the bubbles of steam formed at bottom rises to cooler water and condense, hence they disappear. At the time of boiling, temperature of entire mass of water will be 100°C. Now the bubbles reaches top and then escape.

1. Latent Heat:
The amount of heat per unit mass transferred during change of state of substance is called latent heat of substance for the process.
Eg: Latent heat of vaporization (L_v), Latent heat of fusion (L_f).
If ‘m’ is quantity of substance which undergoes change of state and Q is amount of heat required, then latent heat
L = \(\frac{Q}{m}\)
Latent heat is characteristic of substance and it depends on pressure. Its unit is JKg^-1.

Question 5.
Draw the temperature versus heat diagram for water. Mark the three phases of water (including its change of state).
Give reasons forthe following

1. The slope of phase line during change of state iszero.
2. The slope of phase line forthe three phases are different.

Answer:

1. During change of state temperature remains constant.
2. Specific heats of different phases are different.

Question 6.
Burns from steam are usually more serious than boil-ing water. Why?
Answer:
Latent heat of vaporization for water is 22.6 × 10⁵J Kg^-1 (ie; 22.6 × 10⁵J heat is required to convert 1 kg of water into steam at 100°C). So at 100°C, steam carries 22.6 × 10⁵J. (more heat than water).

Heat Transfer
Heat transfer occurs due to temperature difference. The three modes of heat transfer are

1. conduction
2. convection
3. radiation.

1. Conduction:
In conduction, heat transfers between two adjacent parts of a body due to temperature difference. Heat conduction can be considered as time rate of heat flow (heat current). At steady state the time rate of heat flow (H) is proportional to temperature difference ∆T area of cross section (A) and inversely proportional to length of conductor (L).

K is called thermal conductivity.
Its unit is JS^-1m^-1K^-1 or Wm^-1K^-1.

Question 7.
Some cooking pots have copper coating on its bottom. Why?
Answer:
Because of high thermal conductivity of copper, it distributes heat over the bottom of pot very quickly and promotes uniform cooking.

Note: In the house with concrete roof, a layer of insulatiori is made on the ceiling to prevent heat transfer and hence to keep the room cooler.

2. Convection:
In convection, different parts of fluid moves from one point to other. Convection can be natural of forced.
In natural convection when fluid is heated, it expands and becomes less dense. It then rises up and colder part replaces it. This process goes on as a cycle.

Question 8.
Explain the reason for sea breeze
Answer:
During the day, land heats up more quickly than water in lake (due to high specific heat capacity of water). The air on the surface of earth gets heated, expands, becomes less dense and rises up. The colder air (wind) replaces the space created by hot air. It creates a sea breeze. At night the land loses its heat very quickly than water. So water remains more warmer at night.

Note: In forced convection, material is forced to move by pump or by other physical means. Some examples are cooling system of automobile engines, heart that circulate blood throughout our body.

3. Radiation:
In radiation, energy is transferred in the form of electromagnetic radiation called heat radiation. Medium is not required for heat transfer. Earth receives energy from sun by means of radiation.

Thermal radiation:
The electromagnetic radiation entitled by a body by virtue of its temperature is called thermal radiation.

Question 9.
The untensils for cooking purpose are blackened at the bottom. Why?
Answer:
This is to absorb maximum heat from fire and hence to fast up cooking.

4. Black body radiation:
Black body:
A black body is one which absorbs radiations of all wavelengths incident on it. When a black body is heated it will emit radiations of all possible wavelengths. The wavelengths emitted by a perfect black body are called black body radiations.
Energy distribution in a black body radiation:

Lummer and Pringsheim performed an experiment to study the distribution of energy (among the radiation emitted by a black body) at different temperatures.
Result of experiment:
1. Fora given temperature the energy distribution is not uniform.

2. The energy associated with both longer and shorter wavelength of radiation emitted is small.

3. For each temperature there exists a particular wavelength corresponding to which the energy associated is maximum (λm).

4. This maximum energy carrying wavelength (λm) decreases with an increase in temperature of the black body.

5. The area under each curve represents the total energy emitted by the body at a particular temperature.

This area increases with increase of temperature. It is found that area is directly proportional to the fourth power of absolute temperature,
ie. E a T⁴
Wein’s displacement law:
Wein’s displacement law states that the product of the wavelength corresponding to maximum energy (λm) and the absolute temperature of black body is constant.
ie. λmT = constant
The value of the constant (Wein’s constant) is 2.9 × 10^-3mK.
This law explains why the colour of a piece of iron heated in a hot flame first becomes dull red, then reddish yellow and finally white hot.

Wein’s law is useful for estimating the surface temperatures of moon, sun and other stars. If red and blue stars emit radiations of continuous wavelengths, then blue star is hotter than red star.

Stefan’s law of radiation:
Stefan’s law states that the total radiant energy emitted persecond from unit area of the surface of a black body is directly proportional to the fourth power of its absolute temperature.
E a T⁴
E = sT⁴

Green house effect:
The earth surface is a source of thermal radiation because it absorbs energy received from sun. The wavelength of this radiation lies in the infrared region. But a larger portion of this radiation is absorbed by greenhouse gases, (CO₂, CH₄, etc).

This heats up the atmosphere. The net result is heating up of earths surface and atmosphere. This is known green house effect.

Newtons laws of cooling
According to Newton’s law of cooling the rate of loss of heat is directly proportional to difference of temperature between the body and its surroundings.

T₁ is temperature of surrounding medium and T₂ is temperature of body. K is constant that depends on nature of surface and area of exposed surface.
Note:

• The law is applicable for small temperature difference.
• For small temperature difference, cooling occurs due to a combination of conduction, convection, and radiation.
• The graph between difference in temperature and time is as shown in figure.

Students can Download Chapter 2 Animal Kingdom Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 2 Animal Kingdom

BASIS OF CLASSIFICATION:
The fundamental features used in animal classification are:

1. Arrangement of cells
2. body symmetry
3. nature of coelom
4. patterns of digestive
5. circulatory or reproductive systems.

Levels of Organisation:

For example, the digestive system in Platyhelminthes has only a single opening to the outside of the body that serves as both mouth and anus, and is hence called incomplete. A complete digestive system has two openings, mouth and anus.
The circulatory system are of two types:

Symmetry:
Animals can be categorised on the basis of their symmetry.

Diploblastic and Triploblastic Organisation:

Coelom:
The body cavity, which is lined by mesoderm is called coelom. Animals possessing coelom are called coelomates e.g.annelids, molluscs, arthropods, echinoderms, hemichordates and chordates. In some animals, the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm.

Such animals are called pseudocoelomates, eg: aschelminthes. The animals in which the body cavity is absent are called acoelomates, eg: platyhelminthes

Segmentation:

Notochord:
Notochord is a mesodermally derived rod-like structure formed on the dorsal side during embryonic development in some animals. Animals with notochord are called chordates and those animals which do not form this structure are called non-chordates, eg: porifera to echinoderms.

CLASSIFICATION OF ANIMALS:

Phylum – Porifera:
Members are commonly Known as sponges. They are marine and asymmetrical animals. These are primitive multicellular animals and have cellular level of organisation.

1. Sponges have a water transport or canal system. Water enters through minute pores (ostia) in the body wall into a central cavity, spongocoel (Choanocytes or collar cells line the spongocoel and the canals), from where it goes out through the osculum.
2. This pathway of water transport is helpful in food gathering, respiratory exchange and removal of waste.
3. Digestion is intracellular. The body is supported by a skeleton made up of spicules or spongin fibres.
4. Sexes are not separate (hermaphrodite)
5. Sponges reproduce asexually by fragmentation
6. Fertilisation is internal and development include larval stage which is.morphologically distinct from the adult.

Examples: Sycon (Scypha), Spongilla (Fresh water sponge) and Euspongia (Bath sponge).

Phylum – Coelenterata (Cnidaria):
They are aquatic, marine and radially symmetrical animals
1. The name cnidaria is derived from the cnidoblasts or cnidocytes present on the tentacles and the body. Cnidoblasts are used for anchorage, defense and for the capture of prey.

2. Cnidarians are dipioblastic animals. They have a central gastrovascular cavity with a single opening, hypostome.

3. Digestion is extracellular and intracellular. For example , corals have a skeleton composed of calcium carbonate.

4. Cnidarians exhibit two basic body forms called polyp and medusa

Structure of polyp and medusa:
Polyps are sessile and cylindrical form eg: Hydra, Adamsia, etc. whereas, medusa are umbrella-shaped and free-swimming like Aurelia or jelly fish. They exhibit alternation of generation (Metagenesis), i.e. polyps produce medusae asexually and medusae form the polyps sexually (eg: Obelia).

Examples: Physalia (Portuguese man-of-war), Adamsia (Sea anemone),Pennatula (Sea-pen), Gorgonia (Sea-fan) and Meandrina (Brain coral).

Phylum – Ctenophora:
They incude sea walnuts or comb jellies are marine, radially symmetrical, dipioblastic organisms with tissue level of organisation.

1. The body bears eight external rows of ciliated comb plates, which help in locomotion
2. Digestion is both extracellular and intracellular.
3. Bioluminescence is well-marked in ctenophores.
4. Sexes are not separate. Reproduction takes place only by sexual means.
5. Fertilisation is external with indirect development.

Examples: pleurobrachia and ctenoplana.

Phylum – Platyhelminthes:

1. They have flattened body and called as flatworms
2. Flatworms are bilaterally symmetrical, triploblastic and acoelomate animals with organ level of organisation.
3. Hooks and suckers are present in the parasitic forms. Some of them absorb nutrients from the host directly through their body surface.
4. Specialised cells called flame cells help in osmoregulation and excretion.
5. Sexes are not separate.
6. Fertilisation is internal and development is through many larval stages. Some members like Planaria possess high regeneration capacity.

Examples: (a) Taenia (Tapeworm), (b) Fasciola (Liver fluke).

Phylum – Aschelminthes:
The body is circular and called as roundworms. They may be freeliving, aquatic and terrestrial or parasitic in plants and animals.

1. Roundworms have organ-system level of body organisation.
2. They are bilaterally symmetrical, triploblastic and pseudocoelomate animals.
3. Alimentary canal is complete and called as muscular pharynx. An excretory tube removes body wastes from the body cavity through the excretory pore.
4. Sexes are separate (dioecious)
5. Fertilisation is internal and development may be direct or indirect.

Examples Ascaris (Round Worm), Wuchereria (Filaria worm), Ancylostoma (Hookworm).

Phylum – Annelida:
They may be aquatic (marine and fresh water) orterrestrial; free-living, and sometimes parasitic.

1. They exhibit organ-system level of body organisation and bilateral symmetry. They are triploblastic, metamerically segmented and coelomate animals.
2. Their body surface is distinctly marked out into segments or metameres and hence, the phylum called as Annelida.
3. Aquatic annelids like Nereis possess lateral appendages, parapodia, which help in swimming.
4. A closed circulatory system is present.
5. Nephridia help in osmoregulation and excretion.
6. Neural system consists of paired ganglia connected by lateral nerves to a double ventral nerve cord.
7. Nereis, an aquatic form, is dioecious, but earthworms and leeches are monoecious.
8. Reproduction is sexual. Examples: Nereis, Pheretima (Earthworm) and Hirudinaria (Blood sucking leech).
   

Phylum – Arthropoda:
This is the largest phylum includes insects.

1. They have organ-system level of organisation.
2. They are bilaterally symmetrical, triploblastic. segmented and coelomate animals.
3. The body of arthropods is covered by chitinous exoskeleton.
4. The body consists of head, thoraxand abdomen. They have jointed appendages (arthros-joint, poda-appendages).
5. Respiratory organs are gills, book gills, book lungs or tracheal system.
6. Circulatory system is of open type. Sensory organs like antennae, eyes (compound and simple),
7. statocysts or balance organs are present.
8. Excretion takes place through malpighian tubules. They are mostly dioecious.
9. Fertilisation is usually internal.
10. They are mostly oviparous.

Example:

1. Economically important insects: Apis (Honey bee), Bombyx (Silkworm), Laccifer(Lac insect)
2. Vectors: Anopheles, Culexand Aedes(Mosquitoes)
3. Gregarious pest: Locusta (Locust)
4. Living fossil: Limulus (King crab).

Phylum – Mollusca:
This is the second largest animal phylum

1. Molluscs are terrestrial or aquatic (marine or freshwater) having an organ- system level of organisation.
2. They are bilaterally symmetrical, triploblastic and coelomate animals.
3. Body is covered by a calcareous shell and is unsegmented with a distinct head, muscular foot and visceral hump.
4. The space between the hump and the mantle is called the mantle cavity in which feather-like gills are present. They have respiratory and excretory functions.
5. The anterior head region has sensory tentacles. The mouth contains a file¬like rasping organ for feeding, called radula.
6. They are usually dioecious and oviparous with indirect development.

Examples: Pila (Apple snail), Pinctada (Pearl oyster), Sepia (Cuttlefish), Loligo (Squid), Octopus (Devil fish), Aplysia (Seahare), Dentalium (Tusk shell) and Chaetopleura (Chiton).

Phylum – Echinodermata:

1. These animals have an endoskeleton of calcareous ossicles,
2. All are marine with organ-system level of organisation.
3. The adult echinoderms are radially symmetrical but larvae are bilaterally symmetrical.
4. They shows water vascular system which helps in locomotion, capture and transport of food and respiration.
5. They are triploblastic and coelomate animals.
6. Digestive system is complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side.
7. An excretory system is absent. Sexes are separate.
8. (Reproduction is sexual. Fertilisation is usually external.
9. Development is indirect with free-swimming larva.

Examples: Asterias (Starfish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber) and Ophiura (Brittle star).

Phylum – Hemichordata:
Hemichordata is placed as a separate phylum under non-chordata.

1. This phylum consists of a small group of worm-like marine animals with organ-system level of organisation.
2. They are bilaterally symmetrical, triploblastic and coelomate animals.
3. The body is cylindrical and is composed of an anterior proboscis, a collar and a long trunk.
4. Circulatory system is of open type.
5. Respiration takes place through gills.
6. Excretory organ is proboscis gland. Sexes are separate.
7. Fertilisation is external. Development is indirect. Examples: Balanoglossus and Saccoglossus.

Phylum – Chordata:
It is characterised by the presence of a notochord, a dorsal hollow nerve cord and paired pharyngeal gill slits These are bilaterally symmetrical, triploblastic, coelomate with organ- system level of organisation. They possess a post anal tail and a closed circulatory system.
Comparison of Chordates and IMon-chordates:

Phylum Chordata is divided into three subphyla:

1. Urochordata or Tunicata
2. Cephalochordata &
3. Vertebrata.

Subphyla Urochordata and Cephalochordata are often referred to as protochordates and are exclusively marine. In Urochordata, notochord is present only in larval tail, while in Cephalochordata, it extends from head to tail region. Examples: Urochordata – Ascidia, Salpa.Doliolum; Cephalochordata – Branchiostoma (Amphioxus or Lancelet).

All vertebrates are chordates but all chordates are not vertebrates.why?
The members of subphylum Vertebrata possess notochord during the embryonic period. The notochord is replaced by a cartilaginous or bony vertebral column in the adult. Thus all vertebrates are chordates but all chordates are not vertebrates.

Vertebrates have a ventral muscular heart with two, three or four chambers, kidneys for excretion and osmoregulation and paired appendages which may be fins or limbs.
The subphylum Vertebrata is further divided as follows:

Class – Cyclostomata:

1. All living members of the class Cyclostomata are ectoparasites on some fishes. They have gill slits for respiration.
2. Cyclosiomes have a sucking and circular mouth without jaws
3. Their body is devoid of scales and paired fins
4. Cranium and vertebra! column are cartilaginous. Circulation is of closed type.
5. Cyclostomes are marine but migrate for spawning to freshwater. After spawning, within a few days, they die. Their larvae, after metamorphosis, return to the ocean.

Examples: Petromyzon (Lamprey) and Myxine (Hagfish).

Class – Chondrichthyes:

1. have cartilaginous endoskeleton Mouth is located ventrally.
2. Notochord is persistent throughout life.
3. Gil! slits are separate and without operculum (gill cover).
4. The skin is tough, containing minute placoid scales.
5. Teeth are modified placoid scales
6. These animals are predaceous.
7. Due to the absence of air bladder, they have to swim constantly to avoid sinking.
8. Heart is two-chambered (one auricle and one ventricle). ,
9. Some of them have electric organs (e.g., Torpedo) and some possess poison sting (e g., Trygon).
10. They are cold-blooded (poikilothermous) animals, i.e., they lack the capacity to regulate their body temperature.
11. Sexes are separate.
12. In males pelvic fins bearclaspers.
13. They have internal fertilisation and many of them are viviparous.

Examples: Scoliodon (Dog fish), Pristis (Sawfish), Carcharodon (Great white shark), Trygon (Sting ray).

Class- Osteichthyes:
It includes both marine and fresh water fishes with bony endoskeleton.

1. They have four pairs of gills which are covered by an operculum on each side.
2. Skin is covered with cycloid/ctenoid scales.
3. Air bladder is present which regulates buoyancy.
4. Heart is two chambered (one auricle and one ventricle).
5. They are cold-blooded animals. Sexes are separate.
6. Fertilisation is usually external.
7. They are mostly oviparous and development is direct.

Examples: Marine – Exocoetus (Flying fish), Hippocampus (Sea horse); Freshwater – Labeo Rohu), Catla (Katla), Clarias (Magur); Aquarium – Betta (Fighting fish), Pterophyllum (Angel fish).

Class – Amphibia:
Amphibians can live in aquatic as well as terrestrial habitats.

1. Most of them have two pairs of limbs. Body is divisible into head and trunk.
2. The amphibian skin is moist (without scales). The eyes have eyelids.
3. A tympanum represents the ear.
4. Alimentary canal, urinary and reproductive tracts open into a common chamber called cloaca which opens to the exterior.
5. Respiration is by gills, lungs and through skin.
6. The heart is three chambered (two auricles and one ventricle).
7. These are cold-blooded animals.
8. Sexes are separate. Fertilisation is external.
9. They are oviparous and development is direct or indirect.

Examples: Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia).

Class-Reptilia:
The class name represents crawling mode of locomotion.(Latin, repere or reptum, to creep or crawl).

1. They are mostly terrestrial animals and their body is covered by dry and cornified skin, epidermal scales or scutes.
2. They do not have external ear openings.
3. Tympanum represents ear.
4. Heart is usually three-chambered, but four-chambered in crocodiles.
5. Reptiles are poikilotherms.
6. Snakes and lizards shed their scales as skin cast.
7. Sexes are separate. Fertilisation is internal.
8. They are oviparous and development is direct.

Examples: Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard),Calotes (Garden lizard), Crocodilus (Crocodile), Alligator (Alligator). Hemidactylus (Wall lizard), Poisonous snakes – Naja (Cobra), Bangarus (Krait), Vipera (Viper).

Class-Aves:

The characteristic features of Aves (birds) are:

1. The forelimbs are modified into wings.
2. They possess beak
3. The hind limbs have scales and are modified for walking, swimming or clasping the tree branches.
4. Skin is dry without glands except the oil gland at the base of the tail.
5. Endoskeleton is fully ossified (bony) and the long bones are hollow with air cavities (pneumatic).
6. The digestive tract of birds has additional chambers, the crop and gizzard.
7. Heart is completely four chambered.
8. They are warm-blooded (homoiothermic) animals, i.e.,they are able to maintain a constant body temperature.
9. Respiration is by lungs.
10. Air sacs connected to lungs supplement respiration.
11. sexes are separate. Fertilisation is internal.
12. They are oviparous and development is direct.

Example: Corvus (Crow), Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock), modytes (Penguin), Neophron (Vulture).

Class – Mammalia:

1. 1. The characteristic is the presence of milk producing glands (mammary glands) They have two pairs of limbs, adapted for walking, running, climbing, burrowing, swimming or flying
2. The skin of mammals is unique in possessing hair
3. extemal ears or pinnae are present.
4. Different types of teeth are present in the jaw.
5. Heart is four chambered. They are homoiothermous.
6. Respiration is by lungs. Sexes are separate and fertilisation is internal.
7. They are viviparous with few exceptions and development is direct.

Examples: Oviparous – Ornithorhynchus{Platypus)\Viviparous – Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Macaca(Monkey), Rattus (Rat), Canis (Dog), Fells (Cat), Elephas (Elephant), Equus (Horse), Delphinus (Common dolphin), Balaenoptera (Blue whale), Panthera tigris(Tiger), Panthera leo(Lion).

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Kerala Plus One Accountancy Chapter Wise Questions and Answers Chapter 12 Accounting System Using Database Management System

Plus One Accountancy Accounting System Using Database Management System One Mark Questions and Answers

Question 1.
Reports, the need for which is not anticipated is called_______reports.
Answer:
Casual

Question 2.
_______query does not involve use of any query function to produce a summary of data.
Answer:
Simple

Question 3.
_______query prompts the user to enter criteria for selecting a set of records.
Answer:
Parameter

Question 4.
______clause is used to specify the fields to display data or information.
Answer:
SELECT

Question 5.
______is meant to include page number, data and time of report.
Answer:
Design view

Question 6.
The purpose of______is to organise the information of report into categories whereas______arranges information into numerical or alphabetical order.
Answer:
Sorting, sorting order

Question 7.
When saved as_______,the contents of reports can not be modified by the user.
Answer:
Snap shot

Plus One Accountancy Accounting System Using Database Management System Two Mark Questions and Answers

Question 1.
List out the ways in which quarries may be created in MS-access.
Answer:

1. Wizard method
2. Design method
3. SQL view method

Question 2.
List the structure of a good report created in Access.
Answer:
A good report created in Access may be designed using seven sections which taken together constitutes the structure of report design. The structure of a good report should have the following sections in it.

1. Report Header
2. Page Header
3. Group Header
4. Details
5. Group Footer
6. Page Footer
7. Report Footer

Question 3.
List the ways to refine the design of a report.
Answer:
The design of the report created by any methods can be improved upon by making the following additions and modifications to the report.

1. Adding Dates and Page Numbers
2. Adding and Deleting Report Controls
3. Conditionally Formatting Report Controls
4. Grouping Levels and Sorting Order

Question 4.
What do you understand by saving a report as snap-shot?
Answer:
When a report is created it become important to save it in such a manner so that it can be viewed whenever the user feel like doing so. In this context through a snapshot a report may be saved in such a manner so as to be viewed by others without the help of Access. This becomes possible by saving the report as a snapshot file.

As a result, a high quality picture image of each page of report is created with Adobe Acrobat sofware. Other users of the report can then view the report and print any of its pages without being able to modify its contents.

Plus One Accountancy Accounting System Using Database Management System Three Mark Questions and Answers

Question 1.
State what do you understand by accounting reports?
Answer:
An accounting report is basically the physical form of accounting information. Accounting reports are reports which display information that is acquired from data processing and transformed in an organised manner. Here it is worth mentioning that a report is prepared with a definite objective.

Every report is a collection of related information for a particular need and purpose and must meet the twin objectives of reporting; First to reduce the level of uncertainty that is faced by a decision-maker; second to influence the behaviour (or positive actions) of the decision-maker.
Reports can be classified into two broad categories.

Question 2.
Discuss the capabilities of MS Access
Answer:
Capabilities of MS Access are as follows:

1. Storing the data in an organised manner.
2. Enforcing data integrity constraints.
3. Representing complex relationship among data.
4. Restricting unauthorised assess to database.
5. Allowing fast retrieval of data with or without processing by using SQL.
6. Flexibility to create multiple user interface.

Question 3.
What do you mean by Query in Access. Name the types of queries.
Answer:
A query is a request for data or information from a database table. This data may be generated as results returned by structured query language (SQL) or as pictorials, graphic or complex results.
A query is used to extract data from a database in a readable format according to the users request.
Types of queries:
There are several types of queries in access that are used to generate information. Such queries are called “select queries” because they are used to “select” records with a given set of fileds. There are three types of queries.

1. Simple query
2. Parameter queries
3. Summary queries

Question 4.
With the help of an example, briefly state the meaning of parameter queries.
Answer:
A parameter Query is a query that asks you for one or more pieces of information before displaying the data sheet. A parameter query prompts the user to enter Parameters, or criteria through an input box, for selecting a set of records.

A parameter query is useful when there is a need to repeat the same query with different criteria. The criteria, is not constant as in the case of the simple query. While extracting the transactions to prepare ledger accounts, the same set of queries need to be executed for different account codes. Consider the following SQL statement.

In the above query, the PARAMETERS clause is meant to declare the variable Account No. This SQL statement, when executed, prompts the user to provide the value of Account No.

Question 5.
Briefly state the purpose of functions in SQL environment.
Answer:
SQL (Structured Query Language) is the most popular query language for relational DBMS, and most of the commercial relational database management system use SQL or a variant of SQL.

The original version of SQL was called SEQUEL. SEQUEL is a relational Query Language based on neither relational algebra nor relational calculus. It is a non-procedural language where the concept of universal quantifiers is not used.

A block-structured format of English key words is used in this query language. It is intended for interactive use by people who are not specialists in computers. There are three types of functions that are used in SQL statements.

Plus One Accountancy Accounting System Using Database Management System Four Mark Questions and Answers

Question 1.
What do you mean by programmed and casual reports?
Answer:
Accouting information, generated by processing accounting data is gathered to generate an accounting report. An accounting report, in order to be useful, must display information context in such a manner so as to give confidence to the user, influence his behaviour and prompt him to take positive action. Accounting reports can be classified into two broad categories ie. Programmed Report and Casual Report.
1. Programmed Reports:
Programmed reports are reports which contain information useful for decision making in those situations which the users have anticipated to occur. There are two types of reports within this report type.

a. Scheduled Reports:
The reports, which are produced according to a given time frame, are called scheduled reports. The time frame may be daily, weekly, monthly, quarterly or yearly. Some Statement of Cash transactions (Cash book), Statement of Ageing Accounts, Closing Stock Report, Profit and Loss Account and Balance Sheet, etc.

b. On-Demand Reports:
The reports, which are generated only on the triggering of some event, are called on demand reports. Some examples of an demand reports are a Customer’s Statement of Account, Inventory Reorder Report, Stock in hand Report for a Selected Group of items, etc.

2. Casual Reports:
Casual reports are those reports, the need for which is not anticipated, the information content of which may be useful but casually required. These adhoc reports and are generated casually by executing some simple queries without requiring much of professional assistance. As opposed to programmed reports, casual reports are generated as and when required.

Question 2.
Describe and discuss the procedure of creating the receipts side of a cash book.
Answer:
As it is known to all a Cash book is a type of accounting report. The procedure of creating the receipts side of cash book is same as reports generation. In the process of producing receipts side of a cash book, it is necessary to retrieve a set of processed data records which provide information on code (Account Number), Name of Account, Particulars and credit Balance with reference of each account where cash account is debited.

Receipt side of cash book deals with the cash receipts. In the process of creating receipts side we have to find out the amount and particulars of the transaction in which cash is received ie. cash account is debited. For creating it, first we have to find out these amounts and a particular set of SQL statement and save them into Database after giving particular name to each query.

After creating the SQL statement now we will start the process of MS Access Database. Select create report in design view and query (Last Saved). This respond to give blank report design dividend into three sections page header, detail and page footer and of available fields of Query.

Here, we design our report with the tools provided by Access like giving name to the report, defining its size and colour. After this we select the all fields from our Query and drag and drop them into the Detail section. By applying some arithmetical calculations provided by Access we get the receipt, side of cash book.

Plus One Accountancy Accounting System Using Database Management System Five Mark Questions and Answers

Question 1.
“MS-Access supports different data types”. What are the different data types?
Answer:
The following are the different data types:

1. Text: It is used for a string of character: Words or numbers that are not to be used in arithmetic calculations. The maximum length for a text field is 255 characters. It is the default data type. For example – Job name, Job department, Job type.
2. Memo: It is used for storing comments and is capable of accommodating 65,536 characters.
3. Number: It is meant to store numbers, which could be integers, long integers, bytes, single, double or decimal types. For example – Job unit, Job ID.
4. Date / Time: It is used to store dates, time or a combination of both. For example – Job time.
5. Currency: It is used for storing numbers in terms of Dollars, Rupees or other currencies.
6. Auto Number: It is a numeric data automatically entered by access.
7. Yes / No: It is to declare a logical field which may have only one of the two opposite values alternatively given as: Yes or No, On or Off, True or False.
8. OLE object: OLE stands for Object Linking and Embedding. It refers to an object that could be a photograph, barcode image or another document created in another software application.
9. Hyperlink: This data type is meant to store a Universal Resource Locator (URL) and e-mail addresses.

Question 2.
Briefly explain in steps the method of creating a query, using wizard.
Answer:
In order to create a query using Wizard, the following steps are required.
1. Select Queries from Objects list given in LHS (Left Hand Side) of Database window.

2. Double click at Create Query by Using Wizard given on the RHS (Right Hand Side). Immediately, there is a window titled ‘Simple Query Wizard’ that prompts the user to select a field from a table or an existing query that is to be included in the query being created. Many such fields may be selected according to the information requirement of the query.

The tables (or queries) being chosen represents the data source of the query being created. The fields being selected imply the data items to be displayed by the query. Use arrow buttons or double click at the list of fields on LHS of this window to select fields.

3. Click at Next after the desired fields have been selected. If the selected fields include a number or currency field, the designer is prompted to choose an option button to specify whether the query to be created is a summary or detail query.

• If details option is chosen, the execution of query results in displaying records from data source.
• If summary option is selected, the user is prompted to indicate the type of summarisation required: Sum, Average, Minimum and Maximum with respect to the field of summarisation. Clicking at check boxes against different types of summarisation specifies this. Click OK.

4. Click at Next and specify the name of the query being created % Finish to save and execute the query. The results of the query are displayed in datasheet view.

Question 3.
State the procedure for creating ledger in MS Access.
Answer:
Financial Accounting Reports can be generated in MS Access easily. Ledger is one of the financial reports through which accounting transactions are shown in a particular account, during a given period of time. A ledger contains eight columns as follows:

For creating a ledger in MS Access it is necessary to retrieve a set of processed data recordes each of which provide information code (Account Number), Name of Account, Particulars, Date Debit Balance and Credit Balance with reference to each particular account.

For creating Ledger in MS Access we have to take the following steps: First of all, we will selecte the Design View method to generate a Ledger as follows:
1. Select Reports from the object list in Database window.

2. Click at New Button. This displays the New Report Windows.

3. Select Design view and Query L from combo control.

4. Click OK,
Now, the Access will display a blank report which will be there in three sections as Page header, Detail, and Page Footer. The above blank report will be displayed horizontally. Now it will show a list of available fields of Query L for embedding on to this blank design report.

5. Now it’s time to Click at properties of report and select data tab to define the record sources as Query L. This gives a list of available fields of Query L.

6. Now page header and footer will be choose by clicking at the part of report design. As we click, access will provide two more sections ie. Page header and Page footer.

7. Now we will describe the specifications by clicking at the icon of toolbar and pick up a label control to be placed at Page Header section and assign set it caption property to (Account name), Font size to 12. Font colour to Back, Text align to left and Font weight to Bold.

8. Select all the fields of Query L by clicking at every field while keeping the Ctrl key pressed. Drag and Drop the selected field on Details Section.

9. Select the label control of all the six fields by clicking at each while keeping the shift key pressed. Right click at select label control and choose Cut. Place the mouse at Page Header Section and paste these Control.

10. Choose the properties provided by Access.

11. Align the test controls in Detail section.

12. Select the text controls and Amount field and modify their properties.

The above mentioned is the simple procedure through which we can create Ledger in MS Access.

Question 4.
Discuss with a set of inter-related data tables, the basics of creating queries in MS Access?
Answer:
It is a well know fact that Relational Database management system stores data in different table (relations) so that there is no or minimum data redundancy. But for a complete view of data stored across various tables is achieved only by executing Queries based on SQL. A query is capable of displaying record containing field from across a number of data tables.

In other words SQL has statement for data defini-tion, query and update. Besides this, it has the ca-pability to define user oriented views of database; specify security and authorisation, define integrity constraints and various other operations. Various SQL statements are used to create queries for inter-related data tables.

Some of the basics of creating queries in MS Access with a set of inter related data table are here with the help of the following statements.

If we talk about the above query the vouchers table has been joined with Accounts table on the basis of Code field of Accounts and Debit field of Vouchers. The result record set has been grouped on the basis of Code and name of accounts. The sum of amount of each group has been ascertaining and displayed.

We can take another example to understand it better:

In the above query, vouchers table, Account table and Account type table are joined on the basis of Debit Field, code field respectively to retrieve Code, Name, and Category of Expense account which have been debited.

Question 5.
Explain the data base design for Model-I for produc-ing the receipts the series of SQL statements for producing the payment side of cash book for Model- II.
Answer:
The following series of SQL Statement retrieve a record set of producing the payment side of cash . book of Model II.
1. SQL Statement

2. SQL Statement

3. SQL Statement

This SQL Statement is source as Query D1.

4. SQL Statement

This SQL Statement is saved as Query D2.

5. SQL Statement

Plus One Accountancy Accounting System Using Database Management System Six Mark Questions and Answers

Question 1.
Briefly explain the set of SQL statements to produce the receipts side of a cash book for ModeII.
Answer:
The following series of SQL statement retrieve a record set for producing the receipts side of cash book for ModeII.
1. To find the total amount by which the cash account is debited. In order to ascertain the total amount by which every transaction cash account has been debited, the following SQL statement is formed.

This SQL statement gives the code and amount from which cash is received. This SQL statement is saved as Query Cl.

2. To generate the total of Receipt side. The following SQL Statement is formed.

This SQL statement is save as Query C2.

3. To find the record set which consist of account code, Name of account, credit amount and date. The following SQL statement is formed.

Question 2.
Describe in steps the design view method to create a query in MS Access?
Answer:
Design Method:
In order to create a query by design method, the following steps are required.
1. Select Queries from Objects list given in LHS of database window. Double click at Create Query by Using Design View given on the RHS.

2. Access responds by displaying a Select Query and Show Tables Window. The select query window is vertically divided into two panes, upper pane and lower pane. The upper pane is meant to display data sources (Tables or Existing Queries) and the lower pane, which is also called Query By Example (QBE) grid, has one column each for field to be included in query being created.

The row of this grid shows field name, table (or query), sort order, whether the selected field is shown in the query results or not and also the criteria that have been applied to the field or fields to restrict the query results.

The Show Table Window is meant to add tables, queries or both to the upper pane of Select Query Window. If closed, the show Table Window can be recalled by a right click at upper pane % show table.

3. Click at View item of Menu bar % Total and then % Table Names.

4. Click at field row of first column of QBE grid to select the fields to be included in the query. The process is repeated for second and subsequent columns of grid to include more fields in the query. This process of selection constitutes the data items to be displayed by SELECT clause of SQL statement.

5. The name of table or query is displayed, in accordance with selection of fields. Such tables or queries constitute the data sources shown after FROM clauses of SQL statement. However, the initial selection a table/ query in the second row of QBE grid restricts the choice of fields to the selected table/query only.

6. Click at row of grid to specify the Group by clause and aggregate functions so that a summary query is created.

7. Click at row of grid to specify the sort order (Ascending or descending) on field(s). The selected fields for sort order are shown after ORDER BY clause of SQL statement in which ascending order is the choice of default.

8. Click at row to check for the selected field to be displayed in the query result. The field(s) may be selected only for the purpose of specifying the sort order or criteria.

9. Click at row ofthe grid to specify the criteria to limit the records to be displayed by the query being created. The specified criteria result in a conditional expression, which is shown after the WHERE clause of SQL statement.

10. Click File % Save (or Press Ctrl + S) to save a query. A dialog box prompts the user to specify the name of the query being created. By default a generic name appears which can be accepted or rewritten with a desired name.

Question 3.
Explain MS Access and its components.
Answer:
MS Access is one of the popularly used Database Management System (DBMS) to create, store and manage database. It is popularly called Access. Access is functionally available with the following seven object classes. Each of these object classes is capable of creating their respective object replicas.

1. Tables: This object class allows a database designer to create the data tables with their respective field names, data type, and properties.
2. Queries: The stored data is processed using the query facility to produce desired information.
3. Forms: This object class allows the designer to create an appropriate user interface to formally interact with back end database defined by the tables and queries.
4. Reports: This object class is used to create various reports. Such reports are designed in access according to the requirement of end user.
5. Pages: This object class is meant to create data access pages which can be posted on a website of an organisation using internet.
6. Macros: A macro is a list of macro-oriented actions that runs as a unit.
7. Modules: These are the foundation of any application and allow the designer to create a set of programming instructions called functions or sub-routines that can be used throughout the application.

Plus One Accountancy Accounting System Using Database Management System Eight Mark Questions and Answers

Question 1.
Discuss the SQL view method of creating a query.
Answer:
SQL View Method:
A query may be directly specified in Select Query Pane by a right click at table pane % SQL view. The upper and lower panes of selected query window are substituted by a pane to specify the SQL Statement that is written by using keyboard.

The desired SQL statement is directly okeyed in on this pane and saved in the same manner as described for design method. While forming the SQL statement, the following clauses are normally used for generating information (or Select) queries.

1. SELECT:
This clause is used to specify the fields to display data or information. Consider the following SQL statement segment.
SELECT code, Name, Amount
The fields Code, Name and Amount after SELECT clause indicate the data items to be displayed by the query statement.

2. FROM:
This clause is meant to indicate the source of data in terms of tables or queries or a combination of both. Two tables are joined by specifying a JOIN Clauuse based on a condition of Join. There can be three types of Join, Inner, Left and Right.

3. INNER:
This join clause is meant to display only exactly matching records between two data sources. Consider the following SQL statement segment.
FROM Accounts INNER JOIN Account Type
ON (Catld = Type)
In the above statement, only those records of Accounts and Account Type table constitute the source of query data, which match exactly on Catld = Type.

4. LEFT:
With this Join, all the records in the primary table in the relationship are displayed irrespective whether there are matching records in the related table or not. Consider the following SQL statement segment.
FROM Accounts LEFT JOIN Account Type
ON (Catld = Type)
In the above statement, all records of Accounts along with matching records of Account Type table constitute the source of query data, the matching condition is Catld = Type.

5. RIGHT:
With this join, all the records of related table in the relationship are displayed irrespective whether there are matching records in the primary table or not. Consider the following SQL statement.
FROM Accounts RIGHT JOIN Account Type
ON (Catld = Type)
In the above statement, all records of Account Type along with matching records of Accounts table constitute the source of query data. The matching condition is Catld = Type.

6. WHERE:
This clause in SQL statement is used to provide the condition to restrict the records to be returned by query. The resultant records of query must satisfy the condition which is specified after WHERE clause. This is meant to filter records returned by the query.

7. ORDER BY:
This clause is meant to specify the order in which the resultant records of query are required to appear. The basis of ordering is determined by the list of fields specified after the order by clause. Consider the following SQL statement segment.
ORDER BY Type, Code
The above statement in the context of Accounts table implies that the resultant record set is ordered by the Type field of Accounts and within Type, by Code field of Accounts.

8. GROUP BY:
The group by clause is used in the SQL statement to enable grouping of records for creating summary query. The fields after GROUP BY clause constitute the basis of grouping for owhich summary results are obtained. Consider the following SQL statement.

In the above SQL statement, the GROUP BY clause uses Debit account codes as the basis for computing the sum of amount of voucher. The total amount, by which every transacted account has been debited, is given by this SQL statement. In this statement, sum of amount is found for each group of records formed using GROUP BY clause.

Question 2.
Describe the series of SQL statements to produce trial balance data base design for Model-ll is used.
Answer:
Model II:
The following series of SQL statements retrieve the record set for producing trial balance when database design for Model-ll is used. In addition to this, the accounts have been categorised within the trial balance according to the Account Type: Expenses, Revenues, Assets, and Liabilities.

1. To find the Total Amount by which the Accounts have been Debited:
The transacted accounts in design of Model-ll have been stored in AccCode of Vouchers Main and Code of Vouchers Detail:
The following SQL statement is formed to generate the relevant information from Vouchers Details.

voucherMain.Vno= VouchersDetails.Vno

Similarly, the following SQL statement is formed to generate the required information from Vouchers Main table.


voucherMain.Vno= VouchersDetails.Vno
WHERE Type = 1
GROUP BY AccCode;
Both the SQL statements are meant to extract similar sets of records, but from different sources. Therefore, the resultant record set of these SQL statements have been horizontally merged using UNION clause as shown below.

The above SQL statement is saved as Query 101 for its subsequent use. The total of debit amount in this query represents the Total with positive amounts.

2. To find the Total Amount by which the accounts have been credited:
In order to ascertain the total amount by which every transacted account has been credited, a query similar to that in (a) need to be formed.

This is achieved by substituting Debitfield in SELECT and GROUP BY clause by Credit field and the sum of amount generated by sum(Amount) is multiplied by -1 so that the final amount assigned to Total field is always negative. Accordingly, the following SQL statement is formed.

In the above SQL statement, the sum of amount has been multiplied by -1 to ensure that the amount of credit is always negative just as amount of debit is taken as positive. This query is saved as Query 102 for its subsequent use.

3. To find a collective record set of Accounts with their Debit and Credit totals:
A collective record set is generated by forming a union query between Query 101 and Query 102 to ensure that the debit and credit amount with respect to each account becomes available for generating the net amount.
Accordingly, the following SQL statement is formed.

The above SQL statement causes horizontal merger of record sets returned by Query101 and Query102. This SQL statement is saved as Query103 for its subsequent use in next query.

4. To find the Net Amount with which an account has been Debited or Credited:
To generate the net amount, an SQL statement similar to Query04 (designed for query(d) of Model-1) above, is formed as shown below, except that its source of data is Query103 instead of Query03.

This query is save as Query104 for its subsequent use in generating a record set, giving details of information for trial balance.

5. To find the Record set which consists of Account Code, Name of Account Debit Amount and Credit Amount:
This query, which is meant to provide relevant information to the trial balance report, is similar to Query 05 (designed and discussed in (e) of Model-1). Accordingly, the following SQL statement is formed by changing the source of data from Query 05 to Query 105 as shown below.

In above SQL statement, the results of Query104 and data stored in accounts table has been used. This SQL statement is saved as Queryl05 for providing source of information to Trial Balance Report.

Trial Balance with Sorting and Grouping Levels:
In order to prepare a trial balance with all the account duly grouped by and sorted within category of accounts, two additional queries (vi) and (vii) are required.

6. To Find the Record Set of Accounts with their Category and Category ID:
Accounts table is related to Account Type table vide Type field. The following SQL statement, using INNER JOIN clause, is formed to retrieve the relevant fields of various accounts.
SELECT Accounts.Code, Accounts. Name, Category, Catld FROM Accounts
INNER JOIN AccountType ON
Accounts.Type = Account type.Catld;
This SQL statement is saved as Query 106 for its subsequent use in next query.

7. To Find the Record Set consisting of Account Code, Name of Account, Debit Amount and Credit Amount along with Category Details:
This query, when compared with (v) above, reveals that two additional fields Category and Catld are required. Accordingly, the SQL statement stored as Query105 is modified by substituting Accounts table with Query106 to form the following statement.

SELECT a.Code, b.name AS (Name of Account), IIF (a.Net>0, a.Net, null) AS Debit, IIF (a.Net<0, abs(a.Net), null) AS Credit, Category, Catld FROM Queryl 04 AS a. Query106 AS b WHERE a.code = b.code;
This SQL statement is saved as Query107 to provide information details for designing trial balance with grouping and sorting of the accounts.

Question 3.
Using Model-III discuss the series of SQL statements to produce a trial balance up to a particular date.
Answer:
The following series of SQL statement retrieves a record set for producing trial balance when data base is design for ModeII.
1. To find the total amount by which the account have been debited. The following SQL statement will be formed.

GROUP BY clause retrieves the rows of vouchers table accounts wise because the debit field refers to account code. This SQL statement is saved as Query 01. The total of debit amount in this query is given by total yield with positive amounts.

2. To find the total amount by which the accounts have been credited. The following SQL statement will be formed.

The sum of amount generated by Sum(amount) is multiplied by -1 so that the final amount assigned to total field is always negative. The purpose of using negative values is to differentiate between debit and credit totals for each account and also to facilitate the simple arithmetic summation for obtaining the net amount. This SQL statement is saved as Query 01.

3. To generate a collective record set of accounts with their debit and credit totals. Well this collective record set will be generated by executing a union query between Query01 and Query 02. The following SQL statement will be followed in this case.
SELECT*
FROM Query01
UNION SELECT*
FROM Query 02
This SQL statement is saved as Query 03.

4. To generate the net amount with which an account has been debited and credited. The following SQL statement will be formed
SELECT Code, Sum(Total) AS Net
FROM Query 03
GROUP BY Code
A positive net amount implies a debit and negative amount means a credit balance corresponding to an account code. This SQL statement is saved as Query 04 used in generating record set for trial balance.

5. To find that record set which consists of account code, name of account, debit amount and credit amount. The following SQL statement will be formed
SELECT a.Code, b. Name AS (Name of Account),
IIF (a.Net>0, a.Net, null) AS Debit,
IIF (a.Net>0, abs(a.Net), null) AS Credit,
FROM Query 04 AS a, Accounts ASb
WHERE a.code=b.code;
This SQL statement is saved as Query05 for providing the necessary information content for Trial Balance Report.

Students can Download Chapter 1 The Living World Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 1 The Living World

WHAT IS ‘LIVING’?
The features of living organisms are

All living organisms grow, increase the mass and increase the number of individuals are the characteristics of growth.

• In plants, growth by cell division occurs continuously throughout their life span.
• In animals, growth is seen only up to a certain age.
• Unicellular organisms also grow by cell division it can be seen in in-vitro cultures by simply counting the number of cells under the microscope.

• In multicellular organisms, reproduction refers to the production of progeny possessing features more or less similar to those of parents.
• Fungi multiply and spread due to the millions of asexual spores they produce.
• In lower organisms like yeast and hydra reproduce by budding.
• In Planaria (flatworms) a fragmented organism regenerates the lost part of its body and becomes a new organism.
• The fungi, the filamentous algae, the protonema of mosses etc multiply by fragmentation.

All living organisms are made of chemicals. These chemicals are constantly being made and changed into some other biomolecules. There are thousands of metabolic reactions occurring simultaneously inside all living organisms.

Metabolism is a defining feature of all living organisms without exception, isolated metabolic reactions in vitro are not living things but surely living reactions.

• All organisms, from the prokaryotes to the most complex eukaryotes can sense and respond to environmental cues.
• Photoperiod affects reproduction in seasonal breeders, both plants and animals.
• All organisms are ‘aware’ of their surroundings.
• Human being is the only organism who is aware of himself, i.e. self-consciousness.

Living organisms are self-replicating, evolving and self-regulating interactive systems capable of responding to external stimuli. All living organisms are linked to one another by the sharing of the common genetic material, but to varying degrees.

DIVERSITY IN THE LIVING WORLD:

Nomenclature:
There are millions of plants and animals in the world; their names need to be standardised all overthe world. This process is called nomenclature.

Identification:
Nomenclature or naming is only possible when the organism is described correctly and the name is attached to. This is identification.

For plants, scientific names are based on agreed principles and criteria, which are provided in International Code for Botanical Nomenclature (ICBN). For animals International Code of Zoological Nomenclature (ICZN). Biologists follow universally accepted principles to provide scientific names.

For example the scientific name of mango is written as Mangifera indica. In this name Mangifera represents the genus while indica, is a particular species, or a specific epithet Other universal rules of nomenclature are as follows:

Classification:
It is the process by which anything is grouped into categories based on some easily observable characters. Hence, based on characteristics, all living organisms can be classified into different taxa. This process of classification is taxonomy.

Hence, characterisation, identification, classification and nomenclature are the processes that are basic to taxonomy. Sytematics include identification, nomenclature and classification. It also takes into account evolutionary Ktogdom relationships between organisms.

The word systematics is derived from the Latin word ‘systems’ which means systematic arrangement of organisms. Linnaeus used Systems Naturae as the title of his publication.

TAXONOMIC CATEGORIES:
It involves hierarchy of steps that represents a rank or category. Since all categories together constitute the taxonomic hierarchy. Each category, referred to as a unit of classification termed as taxon Insects represent a group of organisms sharing common features like three pairs of jointed legs. It means insects are recognisable give the rank. Each rank or taxon represents a unit of classification.

Common categories as kingdom, phylum or division (for plants), class, order, family, genus and species. In the plant and animal kingdoms species is lowest category.This helps in identifying similarities and dissimilarities among the individuals of the same kind of organisms as well as of Other kinds of organisms.

Species:
The group of individual organisms with fundamental similarities are called species. The species distinguish from other closely related species based on the distinct morphological differences.

For example Mangifera indica, Solanum tuberosum (potato) and Panthera leo (lion). All the three names, indica, tuberosum and leo, represent the specific epithets, while the first words Mangifera, Solanum and Panthera are genera.

Genus:
Genus comprises a group of related species which has more common characters For example, potato, tomato and brinjal are three different species but all belong to the genus Solanum. Lion (Panthera leo), leopard (P pardus) and tiger (P. tigris) with several commodes features are all species of the genus Panthera.

Family:
Family, has a group of related genera with number of similarities. Families are characterised on the basis of both vegetative and reproductive features of plant species.

Solanum, Petunia and Datura are placed in the family Solanaceae. Genus Panthera, comprising lion, tiger, leopard is put along with genus, Fells (cats) in the family Felidae

Order:
Order is the assemblage of families which exhibit a few similar characters. The similar characters are less in number as compared to different genera included in a family.

Plant families like Convolvulaceae, Solanaceae are included in the order polymoniales mainly based on the floral characters. The animal order, Carnivora, includes families like Felidae and Cancidae.

Class:
This category includes related orders. For example, order Primata comprising monkey, gorilla and gibbon is placed in class Mammalia The order Carnivora that includes animals like tiger, cat and dog belongs to the Class Mammalia also.

Phylum:
It includes animals like fishes, amphibians, reptiles, birds along with mammals.

In the case of plants, classes with a few similar characters are placed in the category called Division.

Kingdom:
All animals belonging to various phyla are assigned to the highest category called Kingdom Animalia The Kingdom Plantae, comprises all plants from various divisions.

The taxonomic categories starting with species and ends in kingdom are arranged in ascending order. From species to kingdom, the number of common characteristics goes on decreasing.

TAXONOMICAL AIDS:
The collection of specimens of plant and animal species is essential for taxonomic studies. These are also fundamental to systematics.

Herbarium:
It is a store house of collected plant specimens that are dried, pressed and preserved on sheets. These sheets are arranged according to a universally accepted system of classification. The descriptions on herbarium sheets, become a store house or repository for future use.

The herbarium sheets also carry a label providing information about date and place of collection. Herbaria also serve as quick referral systems in taxonomical studies.

Botanical Gardens:
These are the collections of living plants for reference. Plant species in these gardens are grown for identification purposes. and each plant is labelled indicating its botanical/scientific name and its family.

The famous botanical gardens are at Kew (England), Indian Botanical Garden, Howrah (India) and at National Botanical Research Institute, Lucknow (India).

Museum:
Museums have collections of preserved plant and animal specimens for study and reference. Specimens are preserved in the containers or jars in preservative solutions. Plant and animal specimens may also be preserved as dry specimens.

Insects are preserved in insect boxes after collecting, killing and pinning. Larger animals like birds and mammals are usually stuffed and preserved. Museums have collections of skeletons of animals also.

Zoological Parks:
These are the places where wild animals are kept in protected environments under human care that helps to learn about their food habits and behavior.

Key:
It is used for identification of plants and animals based on the similarities and dissimilarities. The keys are based on the contrasting characters in a pair called couplet. The choice made between two opposite options results in the acceptance and rejection.

Each statement in the key is called a lead. Separate taxonomic keys are required for each taxonomic category such as family, genus and species for identification purposes. Flora, manuals, monographs and catalogues help in correct identification.

Students can Download Chapter 12 International Business – II Notes, Plus One Business Studies Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Business Studies Notes Chapter 12 International Business – II

Contents

• Export procedure – Export documents
• Import procedure – import documents
• Foreign Trade Promotion Measures
• International trade Institutions
• World Bank – IDA – IFC – MIGA – IMF – WTO

Export Procedure:
1. Receipt of enquiry and sending quotations:
The prospective buyer of a product sends an enquiry to different exporters requesting them to send information about price, quality, terms of payment etc. The exporter sends a reply to the enquiry in the form of a quotation referred to as proforma invoice.

2. Receipt of order or indent:
If the buyer is satisfied with the export price and other terms and conditions, he places the order or indent for the goods.

3. Assessing importer’s creditworthiness and securing a guarantee for payments:
After receipt of the indent, the exporter makes necessary enquiry about the creditworthiness of the importer. To mimimise the risk, most exporters demand a letter of credit from the importer.

4. Obtaining export license:
The exporter must apply for export license to the appropriate authority. The following procedure is followed for obtaining the export license.

1. Opening a bank account in any bank authorised by the Reserve Bank of India
2. Obtaining Import Export Code (IEC) number
3. Registration cum Membership Certificate (RCMC) from appropriate export promotion council
4. Registering with Export Credit and Guarantee Corporation (ECGC) in order to safeguard against risks of non payments.

5. Obtaining pre-shipment finance:
After obtaining the export license, the exporter approaches his banker in order to obtain pre-shipment finance for carrying out production.

6. Production or procurement of goods:
Exporter, after obtaining the pre-shipment finance from the bank, proceeds to get the goods ready as per the orders of the importer.

7. Pre-shipment inspection:
Quality control and pre shipment inspection is compulsory in India as per Quality Control and Inspection Act. Inspection certificate is provided by Export Inspection Council. The customs authority permits the shipment of goods only if there is inspection certificate.

8. Excise clearance:
According to Central Excise Tariff Act, excise duty on the material used in manufacturing goods is to be paid. For this purpose exporter apply to the concerned Excise Commissioner in the region with an invoice.

But in many cases the government exempts payment of excise duty or later on refunds it if the goods so manufactured are meant for exports. The refund of excise duty is known as duty drawback.

9. Obtaining certificate of origin:
In order to obtain Tariff concessions or other exemptions, the importer may ask the exporter to send certificate of origin.

10. Reservation of shipping space:
The exporting firm applies to the shipping company for provision of shipping space. Then the shipping company issues a shipping order. A shipping order is an instruction to the captain of the ship that the specified goods after their customs clearance at a designated port be received on board.

11. Packing and forwarding:
The goods are then properly packed and marked with necessary details such as name and address of the importer, gross and net weight, port of shipment and destination, country of origin, etc. The exporter then makes necessary arrangement for transportation of goods to the port,

12.Insurance of goods:
In order to protect the goods against the risk of loss or damage the exporter gets the goods insured with an insurance company.

13.Customs clearance:
The goods must be cleared from the customs before these can be loaded on the ship. For obtaining customs clearance, the exporter prepares the shipping bill. Shipping bill contains particulars of the goods being exported, the name of the ship, the port at which goods are to be discharged, exporter’s name and address, etc. Five copies of the shipping bill along with the following documents are then submitted to the Customs Appraiser at the Customs House.

• Export Contract or Export Order
• Letter of Credit
• Commercial Invoice
• Certificate of Origin
• Certificate of Inspection, where necessary
• Marine Insurance Policy

14. Obtaining mates receipt:
A mate receipt is a receipt issued by the commanding officer of the ship when the cargo is loaded on board, and contains the information about the name of the vessel, berth, date of shipment, description of packages, condition of the cargo at the time of receipt on board the ship etc.

15. Payment of freight and issuance of bill of lading:
The clearing & forwarding agent (C&F agent) hands overthe mate s receipt to the shipping company for the computation of freight. After receipt of the freight, the shipping company issues a bill of lading which serves as an evidence that the shipping company has accepted the goods for carrying to the designated destination.

16. Preparation of invoice:
The exporter prepares an invoice for the dispatched goods. Invoice contains information regarding the quantity of goods sent & the amount to be paid by the importer. It is duly attested by the customs.

17.Securing payment:
After the shipment of goods, the exporter informs the importer about the shipment of goods. Various documents like certified copy of invoice, bill of lading, packing list, insurance policy, certificate of origin and letter of credit are sent by the exporter through his bank.

These documents are required by the importer for getting the goods cleared from customs. The exporter get payment from his bank on the submission of necessary documents called negotiations of the documents.

Documents for Export Transaction:
A. Documents related to goods:
1. Export Invoice:
It is a seller’s bill which contains information about goods like quantity, number of packages, marks on packing, name of ship, port of destination, terms of delivery &, payments etc.

2. Packing List:
A packing list is a statement of the number of cases or packs and the details of the goods contained in these packs.

3. Certificate of Origin:
This is a certificate which specifies the country in which the goods are being produced. This certificate enables the importer to claim tariff concessions or other exemptions.

4. Certificate of Inspection:
For ensuring quality, the government has made inspection of certain goods compulsory by some authorised agency like export Inspection council of India (EICI) etc. After inspecting the goods, the agency issues a certificate of inspection that the consignment has been inspected as required under the export (Quality Control & Inspection) Act, 1963.

B. Documents Related to Shipment:
1. Mate’s Receipt:
A mate receipt is a receipt Issued by the commanding officer of the ship when the cargo is loaded on board, and contains the information about the name of the vessel, berth, date of shipment, description of packages, condition of the cargo at the time of receipt on board the ship etc.

2. Shipping Bill:
The shipping bill is the main document on the basis of which customs office grants permission for the export. It contains full details regarding the goods being exported name of the vessel, exporter s name & address, country of final destination etc.

3. Bill of lading:
It is a document issued by the shipping company after the cargo is loaded on the ship. It is an acknowledgement of goods by the shipping company. It is a document which shows the title to the goods and is freely transferable by endorsement and delivery.

4. Airway Bill:
It is a document issued by the airline company acknowledging the receipt of goods for transshipment through air carriage.

5. Marine Insurance Policy:
It is a certificate of insurance contract whereby the insurance company agrees in consideration of premium to indemnify the insured against loss incurred by perils of the sea.

6. Cart Ticket:
It is also known as cart chit or gate pass. It is prepared by the exporter and contains details regarding export cargo like number of packages, shipping bill number, port of destination etc.

C. Document related to payment:
1. Letter of credit:
A letter of credit is a guarantee issued by the importer’s bank that it will honour up to a certain amount the payment of export bills to the bank of the exporter.

2. Bill of Exchange:
In export & import transaction, exporter draws the bill on the importer asking him to pay a specified amount to a certain person or the bearer of the instrument. The documents required by the importer for claiming title of exported goods are passed on to him only when the importer accepts this bill.

3. Bank Certificate of Payment:
It is a certificate that the necessary documents relating to the particular export consignment have been negotiated and payment has been received in accordance with the exchange control regulations.

Import Procedure:
1. Trade enquiry:
It is a written request by the importer to the exporters for supply of relevant information regarding the price, quality, quantity and various terms and conditions of export etc. Then, the exporter prepares the quotation and sends it to the importer. The quotation is known as proforma invoice.

2. Obtaining import license:
In India it is compulsory to get the IEC number from the Directorate General Foreign Trade ( DGFT).

3. Obtaining foreign exchange:
As foreign exchange transactions are controlled by Reserve Bank of India, the importer has to submit an application along with necessary documents to the RBI to issue foreign exchange.

4. Placing order or indent:
After obtaining the import license, the importer places an import order or indent with the exporter for supply of the specified products. It contains information about the price, quality, quantity of goods ordered, ports of shipment and destination etc..

5. Obtaining letter of credit:
The importer must obtain letter of credit from his bank and send it to the exporter.

6. Arranging for finance:
The importer should make arrangements in advance to pay to the exporter on arrival of goods at the port.

7. Receipt of shipment advice:
After loading the goods on the ship, exporter dispatches the shipment advice to the importer. A shipment advice contains information about the shipment of goods.

8. Retirement of import documents:
After shipping the goods, the overseas supplier prepares necessary documents and hands overto his banker for their onward transmission to the importer when he accepts the bill of exchange. The acceptance of bill of exchange for the purpose of getting delivery of the documents is known as retirement of import documents.

9. Arrival of goods:
When the goods arrive in the importer’s country, the person in charge of the carrier informs the officer in charge at the dock or the airport about it. He provides a document called import general manifest for unloading of cargo. Import general manifest is a document that contains the details of the imported goods.

10. Customs clearance and release of goods:
All the goods imported into India have to pass through customs clearance after they cross the Indian borders. The importer must fulfill the following formalities for clearing the goods.

• Endorsement for delivery
• Payment of dock charges
• Bill of entry

Documents used in an Import Transaction:

1. Trade enquiry:
2. Proforma invoice
3. Import order or indent
4. Letter of credit
5. Shipment advice
6. Bill of lading
7. Airway Bill
8. Bill of entry

Bill of entry:
It is a form supplied by the customs office to the importer who filled it at the time of receiving the goods. It has to be in triplicate and is to be submitted to the customs office. It contains information such as name and address of the importer, name of the ship, number of packages, description of goods, quantity and value of goods, name and address of the exporter, port of destinations, customs duty payable etc.

Foreign Trade Promotion Measures and Schemes:
1. Duty drawback scheme: it refers to the refund of customs and excise duties paid on imported inputs used in the manufacture of export goods.

2. Export manufacturing under bond scheme:
Under this facility firms can produce goods without payment of excise and other duties. The firms can avail this facility after giving an undertaking (i.e. bond) that they are manufacturing goods for export purposes.

3. Exemption from payment of sales taxes:
Goods meant for export purposes are not subject to sales tax. Income derived from export operations had been exempt from payment of income tax. Now this benefit of exemption from income tax is available only to 100 per cent Export Oriented Units (100 per cent EOUs) and units set up in Export Processing Zones (EPZs) or Special Economic Zones (SEZs) for selected years.

4. Advance license scheme:
It is a scheme under which an exporter is allowed duty free supply of domestic as well as imported inputs required for the manufacture of export goods.

5. Export Promotion Capital Goods Scheme (EPCG):
The main objective of this scheme is to encourage the import of capital goods for export production. This scheme allows export firms to import capital goods at zero or concessional rate of import duty.

6. Scheme of recognising export firms as export house, trading house and superstar trading house:
The registered exporters having a record of export performance over a number of years are granted the status of export houses/ trading houses/star trading houses/super star trading houses subject to the fulfillment of annual average export performance.

7. Export of Services:
In order to boost the export of services, various categories of service houses have been recognised, i.e. Service Export House, International Service Export House, International Star Service Export House.

8. Export finance:
Two types of export finances are made available to the exporters by authorised banks. They are termed as pre-shipment finance and post shipment finance. Pre shipment finance is provided to an exporter for financing the purchase, processing, manufacturing or packaging of goods for export purpose. Post-shipment finance is provided to the exporter from the date of extending the credit after the shipment of goods to the export country.

9. Export Processing Zones (EPZs):
They are industrial estates, which form special enclaves separated from the domestic tariff areas. These are usually situated near seaports or airports. They are intended to provide an internationally competitive duty free environment for export production at low cost. They can import capital goods and raw materials for production of export goods without license.

10. 100 percent Export Oriented Units (100 percent EOUs):
These units are established with the main purpose of exporting their entire production except those which are specifically permitted to be sold in the domestic market.

11 .Special Economic Zone (SEZ):
It is specifically a delineated duty free enclave, which is deemed to be a foreign territory for the purpose of trading and imposing duties. It provided an internationally competitive and duty free environment for the production of export of goods.

International Trade Institutions:
Government has set up from time to time various institutions in order to facilitate the process of foreign trade. The Department of Commerce in the Ministry of Commerce is the apex body responsible for regulation and administration of the country’s external trade.
Other organizations are:

1. Export Promotion Councils
2. Commodity Boards
3. Export Inspection Council
4. Indian Institute of foreign trade
5. State Trading Organisation.

All these organizations help exporters by way of promotion of specific export products, quality inspection, participation in trade fairs and exhibitions, conducting training programmes, carrying out overseas researches, disseminating product and market information, and providing packaging consultancy and testing.

Trade Agreements:
At the international level, there are various international organisations such as the World Bank, IMF and WTO for fostering economic cooperation, trade and investments . among the countries.
1. World Bank:
The International Bank for reconstruction and development i.e. World Bank was established in 1945, whose main objectives were to aid the task of reconstruction of the war affected economies of Europe and assist in the development of the underdeveloped nations of the world.
Functions:

• To bring about economic growth and widen the scope of international trade.
• To develop infrastructural facilities such as ‘ energy, transportation etc.
• To help different countries for raising cash crops so that their income rises.
• In addition to providing financial assistance for infrastructure development, agriculture, industry, health etc.

2. International Development Association (IDA):
International Development Association (IDA) was set up in 1960 as a part of the World Bank. IDA was established soft loans primarily to provide soft loans to the poorest countries. So it is called the Soft Loan Window of the IBRD.
Objectives of IDA:

1. To provide development finance on easy terms to the less developed countries
2. To provide assistance for poverty eradication in the poorest countries
3. To provide finance at concessional interest rates in order to promote economic development, raise productivity and living standards in less developed nations
4. To extend macro economic management services relating to health, education, nutrition, human resource development and population control.

3. International Finance Corporation (IFC):
IFC was established in July 1956 in orderto provide finance to the private sector of developing countries. All the members of the World Bank are eligible to become members of IFC.

4. The Multinational Investment Guarantee Agency (MIGA)
The Multinational Investment Guarantee Agency was established in April 1988 to supplement the functions of the World Bank and IFC.
Objectives of MIGA:

• To encourage direct foreign investment into the developing countries
• To. provide insurance cover to investors against political risks
• To provide guarantee against noncommercial risks
• To insure new investments and expansion of existing investments
• To provide promotional and advisory services
• To establish credibility.

5. International Monetary Fund (IMF) International Monetary Fund:
it is the second international organization next to the World Bank. It came into existence in 1945 and its objective is the maintenance of exchange rates and providing short term loans to the countries facing short term foreign exchange problems.
Objectives of IMF:

1. To provide international monetary cooperation through a permanent institution.
2. To facilitate expansion of balanced growth of international trade and to promote and maintain high levels of employment.
3. To promote exchange rate stability among member countries.
4. To help in the establishment of International Payment System.

World Trade Organisation:
The General Agreement for Tariffs and Trade (GATT) was transformed into World Trade Organisation (WTO) with effect from 1 st January 1995. The headquarters of WTO are situated at Geneva, Switzerland.

The World Trade Organization deals with the global rules of trade between nations. Its main function is to ensure that trade flows as smoothly, predictably and freely as possible.

It is concerned with solving trade problems between countries and providing a forum for multilateral trade negotiations. It has a global status similar to that of the IMF and the World Bank. India is a founding member of WTO.
Objectives of WTO:

1. To ensure reduction of tariffs and other trade barriers imposed by different countries
2. To engage in activities which improve the standards of living, create employment, increase Income, facilitate higher production and trade
3. To facilitate the optimal use of the world’s resources
4. To promote an integrated, more viable and durable trading system.

Functions of WTO:

1. To remove barriers of International trade.
2. To Act as a dispute settlement body.
3. To ensure that all the rules regulations prescribed in the Act are duly followed by the member countries for the settlement of their disputes.
4. Laying down a commonly accepted code of conduct for international trade.
5. To consult with IMF, IBRD and its affiliated agencies to bring better understanding and cooperation in global economic policy making.

Benefits of WTO:

1. It helps to promote international peace and facilitates international business
2. All disputes between member nations are settled with mutual consultations
3. It makes international trade and relations very smooth and predictable.
4. Free trade improves the standard of living of the people by increasing the income level
5. Free trade provides an opportunity for getting varieties of qualitative products
6. Economic growth has been increased
7. The system encourages good government.

Students can Download Chapter 11 Structuring Database for Accounting Questions and Answers, Plus One Accountancy Chapter Wise Questions and Answers helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Chapter Wise Questions and Answers Chapter 11 Structuring Database for Accounting

Plus One Accountancy Structuring Database for Accounting One Mark Questions and Answers

Question 1.
_______are known facts that can be recorded and which have implicit meaning.
Answer:
Data.

Question 2.
Data transformation is called_______.
Answer:
Information

Question 3.
Anything in the real world with independent existence is called______.
Answer:
Entity

Question 4.
______represents the database at collection of tables comprising different volumes.
Answer:
Relational Data Model (RDM)

Question 5.
_______is a collection of concepts used to describe the structure of a database.
Answer:
Data Model

Question 6.
A______does not have key attributes of its own.
Answer:
Weak entity

Question 7.
Each simple attribute of an entity type is associated with a value set called______of values.
Answer:
Time ware

Question 8.
When structure of AIS is based on both human and computer resources, it is called______AIS.
Answer:
Liveware

Question 9.
SQL stands for_______.
Answer:
Structured Query Language

Question 10.
_______is a collection of all entity instances of a particular entity type.
Answer:
Entity Set

Question 11.
Qualification of a person is a______attribute.
Answer:
Multi-valued

Question 12.
Height of a person is______attribute.
Answer:
Single valued

Plus One Accountancy Structuring Database for Accounting Two Mark Questions and Answers

Question 1.
What is Database?
Answer:
Database can be defined as “any organised collection of information. It is a centrally controlled integrated collection of logically organised data.
For example: a data regarding purchase order may be required by accountants, financial manager, and purchase managers. In such a case, interrelated data should be properly organised and stored. Such a collection of interrelated data are called ‘database’.

Question 2.
What do you mean by DBMS?
Answer:
A Database Management system is a software system that manages the creation and use of databse. It is a general purpose software system which helps the users in the process of defining, creating, updating, reading, maintaining and protecting the database. All access to the database is through the database management system. It helps the users to obtain data in a more orderly and logical fashion.

Question 3.
What are the functions of DBMS in a supermarket?
Answer:
With the help of DBMS the present volume of sales is known and this information together with past records and perhaps statistics obtained from market research, forms some of the data needed for sales forecasting which in turn influence stock control. Computers are widely used in everyday cash transactions. Computer help to minimise excess stock and release money for other purpose.

Question 4.
What is meant by Null value? What-are the reasons that lead to their occurrence in database relations?
Answer:
Absence of a data item is represented by a special value called null value. There are three situation which may require the use of null values.

• When a particular attributes doesnot apply to an entity.
• Value of an attribute is unknown, although it exists.
• Unknown because it does not exist.

Question 5.
What do you mean by Multi-valued attribute? How is it different from complex and composite attribute?
Answer:
An attribute with multiple values for an entity is called multivalued attributes. For example the qualifications of a person.
The composite attributes can be divided into smaller sub-parts to represent some more basic attributes with independent meanings. For example – Name of a person that is normally subdivided into First name, Middle name, and Last name is a composite attribute.

The composite and Multi-valued attributes may be grouped into constitute “Complex ones”. The paren-thesis () are used for showing grouping of components of composite attributes. The braces {} are used for showing the multi-valued attributes.

Question 6.
State main categories of data model.
Answer:

1. Relational Data Model
2. Hierarchical model
3. Network model

Question 7.
What is a participation role? State the circumstances under which the use of role names becomes necessary in description of relationship types.
Answer:
Each entity type that participates in a relationship type plays a particular role in the relationship. The role name signifies the role that a participating entity of an entity type plays in each relationship instance.

In PREPARED BY relationship type, EMPLOYEE plays the role of document creator and voucher plays the role of document created. Entity TEACHER and Entity STUDENT are related with a relationship TEACHER – teach – STUDENT. The teaches is a participating role in the entity set TEACHER and STUDENT.

Question 8.
Distinguish between stored and derived attribute.
Answer:
Two or more attributes may be related in such a way that one or more becomes basic while other becomes dependent on that basic attribute.
E.g.:- Date of birth of a person is a stored attribute while age of that person is derived attribute.

Plus One Accountancy Structuring Database for Accounting Three Mark Questions and Answers

Question 1.
What are the functions of DBMS in the following organisations?

1. Insurance
2. Railway
3. Bank
4. Telecom department
5. Payroll department

Answer:

1. Insurance – To enter the data relating to the amounts of insurance premium paid, date of payment, date of maturity, etc. and to retrieve the same.
2. Railway – For reservation of railway tickets.
3. Bank – Money can be deposited in one bank and be withdrawn from another bank.
4. Telecom department – Enter customers details, amount of bill, date of payment, etc.
5. Payroll department – To enter the name of the employee, amount and date of payment and type of employees.

Question 2.
What is meant by Key attributes of an Entity type?
Answer:
Every entity has one of its attributes, which contains unique values for identifying the entity instances is called identifier or key attributes of an entity type.
For example, “RollNo” as attribute of Entity type ‘Student’ has unique values through which a student instance can be identified. Similarly, code is a key attribute of entity type ‘Accounts’ because its data values are required to be unique.

Question 3.
What do you understand by relationship type? How is it different from relationship instance and relationship set?
Answer:
Whenever entities from different entity types are related to one another in a particular manner, they constitute a relationship type. The relationship prepared by between the two entity types vouchers and employees associates each voucher with the employees who prepared it.

Similarly, the relationship authorised by between the two entity types, vouchers and employees associate each voucher with the employee who authorises it.

The degree of a relationship type is the number of participating entity types. A relationship type of de-gree two is called binary and that of degree three is called ternary. AVOUCHER (entity), Authorised by (relationship) and EMPLOYEES (entity) together signify a binary relationship.

ASUPPLIER (entity) SUPPLY (relationship) PARTS (entity) to PROJECT (entity) signify a ternary relationship because three entities, namely supplier, parts, and projects are participating in supply relationship in any transaction.
Relationship sets

• 1: 1 (one to one relationship set)
• 1: M (one to many relationship set)
• M: M (Many to many relationship set)

Question 4.
What do you understand by the concept of weak entity used in data modelling? Explain the relevance of owner entity type, partial key and identifying relationship in the context of such modelling.
Answer:
Weak Entity Types:
Entity Types, which do not have identifier (or key attributes) of their own are, called weak entity types. Such entity types are identified by some of their attribute values. These other entity types are called identifying or owner entity type. Accordingly, the relationship type that relates a weak entity type to its owner is called identifying relationship of the weak entity.

A weak entity type always has a total participation constraint (existence dependency) with respect to its identifying relationship because it cannot be identified without its owner entity, eg. a voucher may be accompanied by a set of support documents such as bills, issued by other parties to the transaction, details of which need to be stored. Such SUPPORT DOCUMENT entity type which is used to keep track of support documents attached to each voucher via 1:N relationship is a weak entity.

This is because they are identified as distinct entities only after determining the particular voucher. A weak entity type normally has a partial key, which is a set to attribute that can uniquely identify weak entities that are related to the same owner entity.

Assuming that two support documents of a voucher do not have the same document Id, the said id can be a good partial key. Otherwise a composite attribute of all the weak entity’s attributes will be the partial key.

Question 5.
Define foreign key. How is this concept useful in relational data model? Illustrate with suitable example.
Answer:
While key and entity constraints are specified on individual relation, the referential integrity constraints is specified between two or more relations. This constraint is specified to maintain consistency among the typles of such relations.

Accordingly, a tuple in one relation that refers to another relation must refer to an existing tuple in that other relation. In referencing Accounts type, Accounts relation uses its attributes Type, which acts as foreign key to reference the tuples of relation Accounts type through its primary key Catld.

The value of Type cannot be null because of total participation of Accounts in classify relationship.
Say e.g. there are two tables EMP (EMPNO, ENM, SAL, DPTNO (Foreign key)
DEPT (DPTNO (Primary key), DNM, LOC)
The foreign key DPTNO of EMP table takes its value as a reference from DEPT TABLE DPTNO.

Question 6.
What integrity constraints are specified on database scheme? Why each is considered important?
Answer:
While key and entity constraints are specified on invidividual relation, the referential integrity is specified between two or more relations. This constraint is specified to maintain consistency among the tuples of such relations.

Accordingly, a tuple in one relation that refers to another relation must refer to an existing tuple in that other relation. In referencing Accounts Type, Accounts relation uses its attribute Type, which acts as foreign key to reference the tuples of relation Accounts Type through its primary key Catld. The value of Type cannot be null because of total participation of Accounts in classify relationship.

For example, there are two tables EMP (EMPNO, ENM, SAL, DPTNO (Foreign Key) DEPT (DPTNO {Primary key}, DNM, LOC). The foreign key DPTNO of EMP table takes its value as a reference from DEPT TABLE DPTNO.

Question 7.
In relational data model, a row is called______,a column header is called on_____and the table as
such is called a______.
Answer:

• a row is called a tuple
• a column header is called an attribute
• The table is called a relation.

Plus One Accountancy Structuring Database for Accounting Four Mark Questions and Answers

Question 1.
Explain Entities and Attributes.
Answer:
Entities
Anything in the real world with independent existence is called entity such as an object with physical existence (example – car, person, house) or conceptual existence (example – job, university, account, voucher, a company). In accounting reality, there exist five entities – Accounts, vouchers, employees, accounts type and support documents.

Attributes
Attributes are some properties of interest or characteristics that further describe the entity such as height, weight and date of birth in case of a person and code and name in case of accounts. An entity has a value for each of its attributes, which is the data stored in the database.

In the context of the accounting reality, the following, attributes specific to each entity types have been stated below as:

Question 2.
Discuss the process of designing a Database for Accounting.
Answer:
The process of designing a database for accounting is described below:
1. Reality:
It refers to some aspect of real world situation, for which database is to be designed. In the case of accounting, it is accounting reality that is to be expressed with complete description.

2. ER Design:
This is formal blue print, a pictorial presentation, in which Entity Relations Model concepts are used to represent description of reality.

3. Relational Data Model:
It represents a collection of related data values and hence typically corresponds to real world entity or relationship. It consists of rows and columns.

The table name and column name are used to help in interpreting the meaning of volumes of each rows. Each row of a table is called a data record. All values in a column, which belongs to a particular domain, are of same data type.

4. Normalisation:
This is the process of refining a database design through which the possibility of duplicate or redundant data items is reduced or eliminated.

5. Refinement:
This is the outcome of the process of normalisation. The final database design is arrived at after the process of normalisation is completed. The following chart showing the process of designing a Database for Accounting:

Question 3.
What do you mean by Entity Type? How it is different from entity set?
Answer:
Entity Types and Entity Sets
An entity type is defined as a collection of entities, which share a common definition in terms of their attributes. Each entity type is assigned a name for its subsequent identification. The attributes of entity type are used to describe it in the database. The value of attributes of an entity belonging to entity type are known as “Entity Instance”.

An entity set is a collection of all entity instances of a particular entity type. An entity type is described by a set of attributes called “Schema”. The set of entities pertaining to a particular entity type share the same set of attributes. The collection of entities of a particular entity type is grouped into entity set, called the extension of the entity type.
For example: Entity type: Accounts

Entity set: Collection of entity instances of an entity
Extension or Instances of entity type:

Question 4.
Discuss the basic concepts of Entity Relationship (ER) Model. Illustrate as to how an ER model is diagrammed.
Answer:
It is a popular conceptual data model, which is mostly used in database-oriented applications. The major elements of ER model are entities, attributes, identifiers and relationships that are used to express a reality for which a database is to be designed.

The model is best depected with the help of ER symbols, the list and description of which is shown in figure below. The formal blue print with a pictorial presentation of ER model is called as ER Diagram. While preparing an ER Diagram, the following symbols are used to represent different types of entities, attributes, identifiers, and relationships.

The elements of ER model that are meant to describe and display the reality are discussed in the context of an accounting reality given below.

Question 5.
Discuss the different types of update operations in relation to the integrity constraints which must be satisfied in a relational database model.
Answer:
The following are the update operations in a relation base model. The three basic types of updates are as given below:
1. insert:
This operation is performed to add a new tuple in a relation, eg. an attempt to add another record of an account with data values corresponding to Code, Name and its Type to Accounts relation shall be made by performing insert operation. The insert operation is capable of violating any of the four constraints.

2. Delete:
This operation is carried out to remove a tuple from a relation. A particular data record from a table can be removed by performing such a operation. The delete operation can violate only referential integrity, if tuple being removed is referred by foreign key from other tuples in the database.

3. Modify:
The operation aims at causing a change in the values of some attribute in existing tuples. This is useful in modifying existing values of an accounting record in a data table. Usually, this operation does not cause problems provided the modification is directed on neither primary key or foreign key.

Whenever applied, these operations must enforce integrity constraints specified on relational database schema. Retrieval operation on Relational Data Model does not cause violation of any integrity constraints.

Plus One Accountancy Structuring Database for Accounting Eight Mark Questions and Answers

Question 1.
Discuss the steps you would take to transform an ER Model into various relations of Relational Data Model. Give suitable examples.
Answer:
The rules or guidelines required to design the relational database scheme attempt to provide a step by step procedure that transforms ER design into Relational Data Model design to constitute the desired database.
The following specific steps are required to cause its transformation into relational data model.
1. Create a Relation for Every Strong Entity:
For each strong entity type (which has primary key) in ER schema, a separate relation that includes all the simple attributes of that entity is created.

Either choose bn of the key attributes of such an entity as the primary key for this relation, or choose a set of simple attributes that uniquely identify this entity as the primary key of the relation so created,

eg. employee entity is strong because its finds its primary key in Empld which is one of its unique attribute. Therefore, a separate relation for employee has been created as shown below.

Employee (Empld, Fname, Minit, Lname, Address, PhoneNo, Superld). Similarly, separate relations need be created for the following strong entities whose Primary key attribute have been underlined.

• Accounts (Code, Name, Type)
• Vouchers (VNo, vDate, amount, narration)
• Accounts Type (Catld, Category)

2. Create a separate relation for each weak entity type:
Every weak entity has an owner entity and an identifying relationship through which such weak entity type is identified. For every weak entity type, a separate relation is created by including its attributes. The primary key of this new relation is the combination of its unique attribute(s) for a particular tuple of the owner relation along with primary key attribute of such owner relation.

Furthermore, the primary key of owner entity is included as foriegn key in such a relation key of owner entity and the partial key of weak entity, eg. Support entity, with Vouchers as its owner Entity, does not have a primary key of its own.

It has partial key which is the Sno assigned to each document. Therefore, the Primary key of Vouchers, Vno along with Sno is designed as composite key for support entity and the relation so formed is shown below as
Support (vNo, Sno, dName, sDate)

3. Identify Entity Types Participating in Binary 1: N Relationship Type:
Identify the first relation on n-side of relationship and second on 1-side of such relationship. The primary key of second relation should be included in first relation as its foreign key. eg. An employee can authorize a number of vouchers. It implies that Vouchers entity participates in Auth.

By relationship on n-side while Employees entity participates in same relationship on 1-side. Therefore, the vouchers relation as already formed above in step 1, must also include as foreign key the primary key of Employees, which is Empld.

4. Identify Entity Types Participating in Binary M: N Relationship Type:
For each binary M: N relationship type, create a new relation to represent such relationship. This new relation should include as foreign keys, the primary keys of the relations that represent the participating entity types.

Students can Download Chapter 14 Environmental Chemistry Notes, Plus One Chemistry Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Chemistry Notes Chapter 14 Environmental Chemistry

Introduction
Environmental chemistry deals with various chemical phenomena occurring in the environment. Environmental chemistry deals with the study of the origin, transport, reactions, effects and fates of chemical species in the environment.

Environmental Pollution
The undesirable changes which have harmful effect on plants, animals and human beings is called environmental pollution. A substance, which causes pollution, is known as pollutant.

Atmospheric Pollution
The atmosphere that surrounds the earth is not of ‘ the same thickness at all heights. There are concentric layers of air or regions and each layer has different density. The lowest region of atmosphere in which the human beings along with other organisms live is called troposphere. Above the troposphere, lies stratosphere. Troposphere is a turbulent, dusty zone containing air, much water vapour and clouds. This is the region of strong air movement and cloud formation. The stratosphere, on the other hand, contains dinitrogen, dioxygen, ozone and little water vapour. Atmospheric pollution is generally studied as tropospheric and stratospheric pollution. The presence of ozone in the stratosphere prevents about 99.5 per cent of the sun’s harmful ultraviolet (UV) radiations from reaching the earth’s surface and thereby protecting humans and other animals from its effect.

Tropospheric Pollution
Tropospheric pollution occurs due to the presence of undesirable solid or gaseous particles in the air. The following are the major gaseous and particulate pollutants present in the troposphere:
1) Gaseous air pollutants:
These are oxides of sulphur, nitrogen and carbon, hydrogen sulphide, hydrocarbons, ozone and other oxidants.
2) Particulate pollutants:
These are dust, mist, fumes, smoke, smog, etc.

1. Gaseous air pollutants
a) Oxides of Sulphur:
Oxides of sulphur are produced when sulphur containing fossil fuel is burnt. It has been reported that even a low concentration of sulphur dioxide causes respiratory diseases e.g., asthma, bronchitis, emphysema in human beings. Sulphur dioxide causes irritation to the eyes, resulting in tears and redness. High concentration of SO₂ leads to stiffness of flower buds which eventually fall off from plants.
2SO₂ (g) + O₂ (g) → 2SO₃ (g)
The reaction can also be promoted by ozone and hydrogen peroxide.
SO₂ (g) + O₃ (g) → SO₃ (g) + O₂ (g)
SO₂(g) + H₂O₂(l) → H₂SO₄(aq)

b) Oxides of Nitrogen :

NO reacts instantly with oxygen to give NO₂
2NO(g) + O₂ (g) → 2NO₂ (g)

Rate of production of N02 is faster when nitric oxide reacts with ozone in the stratosphere.
NO(g) + O₃ (g) → NO₂ (g) + O₂ (g)

The irritant red haze in the traffic and congested places is due to oxides of nitrogen. Higher concentrations of NO₂ damage the leaves of plants and retard the rate of photosynthesis. Nitrogen dioxide is a lung irritant that can lead to an acute respiratory disease in children. It is toxic to living tissues also. Nitrogen dioxide is also harmful to various textile fibres and metals.

c) Hydrocarbons:
Hydrocarbons are composed of hydrogen and carbon only and are formed by incomplete combustion of fuel used in automobiles. Hydrocarbons are carcinogenic, i.e., they cause cancer. They harm plants by causing ageing, breakdown of tissues and shedding of leaves, flowers and twigs.

d) Oxides of Carbon :
i) Carbon monoxide:
Carbon monoxide is mainly released into the air by automobile exhaust. Other sources, which produce CO, involve incomplete combustion of coal, firewood, petrol, etc. Many vehicles are poorly maintained and several have inadequate pollution control equipment resulting in the release of greater amount of carbon monoxide and other polluting gases. CO binds to haemoglobin to form carboxyhaemoglobin, which is about 300 times more stable than the oxygen-haemoglobin complex. In blood, when the concentration of carboxyhaemoglobin reaches about 3-4 per cent, the oxygen carrying capacity of blood is greatly reduced. This oxygen deficiency results into headache, weak eyesight, nervousness and cardiovascular disorder. This is the reason why people are advised not to smoke. In pregnant women who have the habit of smoking the increased CO level in blood may induce premature birth, spontaneous abortions and deformed babies.

ii) Carbon dioxide:
Carbon dioxide (CO₂) is released into the atmosphere by respiration, burning of fossil fuels for energy, and by decomposition of limestone during the manufacture of cement. It is also emitted during volcanic eruptions. Carbon dioxide gas is confined to troposphere only. Normally it forms about 0.03 per cent by volume of the atmosphere. With the increased use of fossil fuels, a large amount of carbon dioxide gets released into the atmosphere. Excess of CO₂ in the air is removed by green plants and this maintains an appropriate level of CO₂ in the atmosphere. Green plants require CO₂ for photosynthesis and they, in turn, emit oxygen, thus maintaining the delicate balance. As you know, deforestation and burning of fossil fuel increases the CO₂ level and disturb the balance in the atmosphere. The increased amount of CO₂ in the air is mainly responsible for global warming.

Global Warming and Greenhouse Effect
Greenhouse effect:
Though carbon dioxide is not toxic, the excess concentration of it can lead to changes in climatic conditions, especially by raising the global tempreature. Greenhouse ef- feet is the phenomenon in which earth’s atmosphere traps the heat from the sun and prevents it from escaping into outer space resulting in the rise of atmospheric temperature.

The earth’s atmosphere allows most of the sunlight that falls on it to pass through and heats the surface of the earth. But the heat radiated by the heated surface in the form of infrared radiation is absorbed by greenhouse gases such as CO₂, CH₄, O₃, chlorofluoro carbon compound, water vapour etc. Thus these gases prevent the heat radiation of the earth to go out in space.

As more and more infrared, radiations are trapped, the atmosphere becomes hotter and the global temperature rises up. This is known as global warming. There has been a marked increase in the levels of carbon dioxide in the atmosphere due to severe deforestation and burning of fossil
fuels. An increase in average global temperature is likely to increase infectious diseases such as yellow fever, dengue fever etc. Global warming leads to heating up of water which in turn results in an increase of water level in oceans, lakes, etc.

Acid Rain
Rain water has a pH of 5.6 due to the presence of H⁺ ions formed by the reaction of rainwater with carbon dioxide present in the atmosphere.
H₂P(l) + CO₂(g) \(\rightleftharpoons \) H₂CO₃(aq)
H₂CO₃(aq) \(\rightleftharpoons \) H⁺(aq) + HCO₃^–(aq)

When the pH of the rain water drops below 5.6, it is called acid rain. Acid rain is a byproduct of a variety of human activities that emit the oxides of sulphur and nitrogen in the atmosphere. As mentioned earlier, burning of fossil fuels (which contain sulphur and nitrogenous matter) such as coal and oil in power stations and furnaces or petrol and diesel in motor engines produce sulphur dioxide and nitrogen oxides. SO₂ and NO₂ after oxidation and reaction with water are major contributors to acid rain because polluted air usually contains particulate matter that catalyse the oxidation.
2SO₂(g) + O₂ (g) + 2H₂O(I) 2H₂SO₄(aq)
4NO₂(g) + O₂(g) + 2H₂O(I) 4HNO₃(aq)

Ammonium salts are also formed and can be seen as an atmospheric haze (aerosol of fine particles). Aerosol particles of oxides or ammonium salts in raindrops result in wet deposition. S02 is also absorbed directly on both solid and liquid ground surfaces and is thus deposited as dry-deposition. Acid rain is harmful for agriculture, trees and plants as it dissolves and washes away nutrients needed for their growth. It causes respiratory ailments in human beings and animals. When acid rain falls and flows as ground water to reach rivers, lakes etc. it affects plants and animal life in aquatic ecosystem. It corrodes water pipes resulting in the leaching of heavy metals such as. iron, lead arid copper into the drinking water. Acid rain damages buildings and other structures made of stone or metal. The Taj Mahal in India has been affected by acid rain.

2. Particulate pollutants
The term particulate refers to finely divided solid or liquid particles suspended in air. The particulates usually present in atmosphere are fly ash, soot, dust, metal particles, asbestos dust, solid hydrocarbons, smoke, sulphuric acid and nitric acid mists.

Minute living organisms such as fungi, moulds, algae etc. dispersed in air are called viable particulates. Particles formed either by breakdown of larger materials or by condensation of minute particles are called non-viable particulates, eg: Mists, fumes, smoke, dust etc.

Smog
The word smog is derived from smoke and fog.
This is the most common example of air pollution that occurs in many cities throughout the world. There are two types of smog:

a) Classical smog
occurs in cool humid climate. It is a mixture of smoke, fog and sulphur dioxide. Chemically it is a reducing mixture and so it is also called as reducing smog.

b) Photochemical smog
occurs in warm, dry and sunny climate. The main components of the photochemical smog result from the action of sunlight on unsaturated hydrocarbons and nitrogen oxides produced by automobiles and factories. Photochemical smog has high concentration of oxidising agents and is, therefore, called as oxidising smog. Formation of photochemical smog – When fossil fuels are burnt, a variety of pollutants are emitted into the earth’s troposphere. Two of the pollutants that are emitted are hydrocarbons (unburnt fuels) and nitric oxide (NO). When these pollutants build up to sufficiently high levels, a chain reaction occurs from their interaction with sunlight in which NO is converted into nitrogen dioxide (NO₂). This NO_{2, in turn,} absorbs energy from sunlight and breaks up into nitric oxide and free oxygen atom.

Ozone is a toxic gas and both NO₂ and O₃ are strong oxidising agents and can react with the unburnt hydrocarbons in the polluted air to produce chemicals such as formaldehyde, acrolein and peroxyacetyl nitrate (PAN).

Effects of photochemical smog
Both ozone and PAN act as powerful eye irritants. Ozone and nitric oxide irritates the nose and throat and their high concentration causes headache, chest pain, dryness of the throat, cough and difficulty in breathing. Photochemical smog leads to cracking of rubber and extensive damage to plant life. It also causes corrosion of metals, stones, building materials, rubber and painted surfaces. Catalytic converters are used in the automobiles, which prevent the release of nitrogen oxide and hydrocarbons to the atmosphere. Certain plants e.g., Pinus, Juniparus, Quercus, Pyrus and Vitis can metabolise nitrogen oxide and therefore, their plantation could help in this matter.

Stratospheric Pollution
Formation and Breakdown of Ozone

The main reason of ozone layer depletion is believed to be the release of chlorofluorocarbon compounds (CFCs), also known as freons. These compounds are non-reactive, non-flammable, non-toxic organic molecules and therefore used in refrigerators, air conditioners, in the production of plastic foam and by the electronic industry for cleaning computer parts etc. Once CFCs are released in the atmosphere, they mix with the normal atmospheric gases and eventually reach the stratosphere. In stratosphere, they get broken down by powerful UV radiations, releasing chlorine free radical.

The chlorine radicals are continuously regenerated and cause the breakdown of ozone. Thus, CFCs are transporting agents for continuously generating chlorine radicals into the stratosphere and damaging the ozone layer. Antarctica reported about depletion of ozone layer commonly known as ozone hole over the South Pole. It was found that a unique set of conditions was responsible for the ozone hole. In summer season, nitrogen dioxide and methane react with chlorine monoxide and chlorine atoms forming chlorine sinks, preventing much ozone depletion, whereas in winter, special type of clouds called polar stratospheric clouds are formed over Antarctica. These polar stratospheric clouds provide surface on which chlorine nitrate formed gets hydrolysed to form hypochlorous acid. It also reacts with hydrogen chloride produced as per reaction to give molecular chlorine.

When sunlight returns to the Antarctica in the spring, the sun’s warmth breaks up the clouds and HOCl and Cl₂ are photolysed by sunlight, as given in reactions.

Water Pollution
Causes of Water Pollution
(i) Pathogens:
The most serious water pollutants are the disease causing agents called pathogens. Pathogens include bacteria and other organisms that enter water from domestic sewage and animal excreta. Human excreta contain bacteria such as Escherichia coli and Streptococcus faecalis which cause gastrointestinal diseases.

Dissolved oxygen (DO) in water:
The concentration of dissolved oxygen in water is of vital importance to aquatic life. Growth of fish is inhibited if the dissolved oxygen level in waterfalls below 6 ppm. Pollution causes decrease in DO level.

Dissolved oxygen (DO) in water is consumed by micro-organisms to oxidise organic matter in sewage. Deoxygenation of water may also take place by the bio-oxidation of nitrogeneous matter.

Biochemical oxygen demand (BOD) :
It is the amount of dissolved oxygen required by microorganisms to oxidise organic and inorganic matter present in polluted water. It is generally expressed in ppm (parts per million). ‘Clean water1 would have a BOD value less than 5 ppm while highly contaminated water (say, river water) could have a BOD value 17 ppm or more.

The amount of oxygen in ppm that would be required to oxidise all the contaminants in water is called chemical oxygen demand (COD).

Nowadays most of the detergents available are biodegradable. However, their use can create other problems. The bacteria responsible for degrading biodegradable detergent feed on it and grow rapidly. While growing, they may use up all the oxygen dissolved in water. The lack of oxygen kills all other forms of aquatic life such as fish and plants. Fertilizers contain phosphates as additives. The addition of phosphates in water enhances algae growth. This process in which nutrient enriched water bodies support a dense plant opulation, which kills animal life by depriving it of oxygen and results in subsequent loss of biodiversity is known as Eutrophication.

International Standards for Drinking Water
The International Standards for drinking water are given below and they must be followed.

Fluoride:
For drinking purposes, water should be tested for fluoride ion concentration. Its deficiency in drinking water is harmful to man and causes diseases such as tooth decay etc. Soluble fluoride is often added to drinking water to bring its concentration upto 1 ppm or 1 mg dm^-3. The F^– ions make the enamel on teeth much harder by converting hydroxyapatite, [3(Ca₃(PO₄)₂.Ca(OH)₂], the enamel on the surface of the teeth, into much harder fluorapatite, [3(Ca₃(PO₄)₂.CaF₂]. However, F- ion concentration above 2 ppm causes brown mottling of teeth. At the same time, excess fluoride (over 10 ppm) causes harmful effect to bones and teeth, as reported from some parts of Rajasthan.

Lead:
Drinking water gets contaminated with lead when lead pipes are used for transportation of water. The prescribed upper limit concentration of lead in drinking water is about 50 ppb. Lead can damage kidney, liver, reproductive system etc.

Sulphate:
Excessive sulphate (>500 ppm) in drinking water causes laxative effect, otherwise, at moderate levels it is harmless.

Nitrate:
The maximum limit of nitrate in drinking water is 50 ppm. Excess nitrate in drinking water can cause disease such as methemoglobinemia (‘blue baby’ syndrome).

Soil Pollution
Any factor which destroys the quality, texture and mineral content of the soil or which disturbs the biological balance of the organisms in the soil is referred to as soil pollutant.

Soil pollution has adverse effect on plant growth. Soil pollution is mainly due to

• Indiscriminate use of fertilizers, pesticides etc.
• Dumping of waste materials.
• Deforestation.

Large number of pesticides are used to save plants from pests, rats, insects, fungi etc. Chlorinated hydrocarbons, malathion, aldrin, DDT, BHC etc. are some substances used extensively in agriculture. Herbicides are used to kill weeds. Sodium chlorate (NaClO₃), sodium arsenite (Na₃AsO₃) etc. are widely used as herbicides. Inorganic arsenic compounds are toxic to mammals. Fungicides are important because they counter the growth of fungi. Organo-mercury compounds are used to fungicides. However, these compounds break down in the soil causing harmful effects on human beings. Dumping of paper, plastics and other toxic substances in the soil creates serious problems. A large number of heavy metals get deposited in the soil around smelting industries. These effluents, in the long run, pollute the soil.

Control of environmental pollution
Both industrial and domestic wastes need treatment for safe disposal, (i) Recycling of wasters not only saves the cost on raw materials but also reduces waste disposal costs. Collection and recycling of glass, metal scrap, plastics etc. are some examples of industrial recycling, (ii) Sewage water is filtered to remove large solids and then allowed to settle. Solids can settle as a sludge at the bottom while oil, grease etc. float at the surface which can be skimmed off. The sludge is dried and incinerated at high temperature (above 1000°C) in presence of oxygen. Sewage sludge can be degraded by anaerobic digestion by micro-organisms.

Green Chemistry
Introduction
Green chemistry is a way of thinking and is about utilising the existing knowledge and principles of chemistry and other sciences to reduce the adverse impact on environment. Green chemistry is a production process that would bring about minimum pollution or deterioration to the environment. The byproducts generated during a process, if not used gainfully, add to the environmental pollution. Such processes are not only environmentally unfriendly but ‘ also cost-ineffective. The waste generation and its disposal both are economically unsound. Utilisation of existing knowledge base for reducing the chemical hazards along with the developmental activities is the foundation of green chemistry. It is well-known that organic solvents such as benzene, toluene, carbon tetrachloride etc., are highly toxic. One should be careful while using them.

Green Chemistry In Day-To-Day Life
i) Dry Cleaning of Clothes
Tetra chlroroethene (Cl₂C=CCl₂) was earlier used as solvent for dry cleaning. The compound contaminates the ground water and is also a suspected carcinogen. Replacement of halogenated solvent by liquid CO₂ will result in less harm to ground water. These days hydrogen peroxide (H₂O₂) is used for the purpose of bleaching clothes in the process of laundry, which gives better results and makes use of lesser amount of water.

ii) Bleaching of Paper
Chlorine gas was used earlier for bleaching paper. These days, hydrogen peroxide (H₂O₂) with suitable catalyst, which promotes the bleaching action of hydrogen peroxide, is used.

iii) Synthesis of Chemicals
Ethanal (CH₃CHO) is now commercially prepared by one step oxidation of ethene in the presence of ionic catalyst in aqueous medium with a yield of 90%.

Students can Download Chapter 11 International Business – I Notes, Plus One Business Studies Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Business Studies Notes Chapter 11 International Business – I

Contents

• Meaning – reasons for international business Differences between Foreign business and Domestic business
• Scope and Benefits of international business
• Modes of entry into international business – Exporting and Importing – advantages – Limitations
• Contract Manufacturing – advantages – limitations
• Licensing and Franchising – advantages – limitations
• Joint Venture – advantages – limitations
• Wholly Owned Subsidiaries – advantages – limitations

International or external business can be defined as those business activities that take place beyond the geographical boundaries of a country. In other words buying and selling of goods and services between two countries are called external trade.

It involves not only the international movements of goods and services, but also of capital, personnel, technology and intellectual property like patents, trademarks, know how and copyrights.

Reasons for international business:
1. Because of unequal distribution of natural resources and differences in productivity levels, a country cannot produce all that they need

2. Labour productivity and production costs differ among nations due to various socio-economic, geographical and political reasons.

3. Availability of various factors of production such as labour, capital and raw materials differ among nations.

Differences between International Business and Domestic Business:

Scope of International Business:
1. Merchandise exports and imports:
merchandise exports means sending tangible goods abroad, merchandise imports means bringing tangible goods from a foreign country to one’s own country. It is also known as trade in goods (visible trade), include only tangible goods and exclude services.

2. Service exports and imports:
It involves trade in intangibles. It is also known as invisible trade which includes services received from other countries or services rendered to other countries. eg: Tourism and travel, communication, marketing, transportation services etc.

3. Licensing and franchising:
Permitting another party in a foreign country to produce and sell goods under their trademarks, patents or copyright in lieu of some fee is called licensing. Franchising is similar to licensing, but it is a term used in connection with the provision of services.

4. Foreign investments:
Foreign investment involves investments of funds abroad in exchange for financial return. Foreign investment can be of two types.
(a) Direct investments:
Direct investment takes place when a company directly invests in properties such as plant and machinery in foreign countries with a view to undertaking production and marketing of goods and services in those countries. This is also known as Foreign Direct Investment, i.e., FDI.

(b)Portfolio investment:
Under portfolio investment, a company makes investment by acquiring shares or providing loans to a foreign company and earns income by way of dividends or interest on loans.

In this investor does not get directly involved in production or marketing of goods. It simply earns an income by investing in shares, bonds, bills, or notes in a foreign country or providing loans to foreign business firms.

Benefits of International Business:
The benefits of international business to the nations and business firms are.
Benefits to Nations:
1. Earning of foreign exchange:
It helps a country team foreign exchange which can be used for importing capital goods, technology, petroleum products and fertilisers, pharmaceutical products, etc.

2. More efficient use of resources:
External trade enables a country to utilize the available resources in the best possible manner.

3. Improving growth prospects and employment potentials:
External trade helps to accelerate the economic growth and employment opportunities of a country.

4. Increased standard of living:
Foreign trade helps in raising the standard of living of a country.

5. International relation:
External trade helps to promote harmonious and cordial relationship among the nations.

Benefits to Firms:
1. Prospects for higher profits:
When the domestic prices are lower, business firms can earn more profits by selling their products in countries where prices are high.

2. Increased capacity utilisation:
It help firms in using their surplus production capacities and improving the profitability of their operations. Large scale production helps to reduce the cost of production.

3. Prospects for growth:
It helps firms in improving their growth prospects by creating demands for their products in foreign countries.

4. Enhances competition:
External trade enhances competition, which compels the domestic firms to improve technology of production, production process and quality of the products.

5. Improved business vision:
It improves business vision as it makes firms to grow, more competitive and diversified.

Mode of Entry into International Business:
1. Exporting and Importing:
When goods are sold to a foreign country, it is called export trade. When goods are purchasing from a foreign country, it is called import trade.
Advantages:

• It is the easiest way of gaining entry into international markets.
• Business firms are not required to invest that much time and money in host countries.
• It is less risky as compared to other modes of entry into international business

Limitations:

• It involves additional packaging, transportation and insurance costs.
• Exporting is not possible in case the foreign country restricts imports.
• The export firms do not have much contact with the foreign markets.

2. Contract Manufacturing (Outsourcing):
When a firm enters into a contract with one or a few local manufacturers in foreign countries to get certain goods produced as per its specifications it is called contract manufacturing. It is also known as outsourcing and it can take place in following forms.

• Production of certain components
• Assembly of components into final products
• Complete manufacture of the products

Advantages:

• It Permits the international firms to get the goods produced on a large scale without requiring investment in setting up production facilities.
• There is no investment risk involved in the foreign countries.
• It helps to get the products at lower cost
• Local producers in foreign countries can ensure greater utilization of their idle production capacities.

Limitations:
(a) It may affect the quality of the products.

(b) Local manufacturer in the foreign country loses his control over the manufacturing process because goods are produced strictly as per the terms and specifications of the contract.

(c) The local firm cannot sell the contracted output as per their will.

3. Licensing and Franchising:
Licensing is a contractual arrangement in which one firm grants access to its patents, trade secrets or technology to another firm in a foreign country for a fee called royalty. The firm that grants permission is known as licensor and the firm that receives the rights to use technology or patents is called the licensee.

Franchising is similar to licensing. But it is used in connection with the provision of services. The parent company is called the franchiser and the other party to the agreement is called franchisee.
Advantages:

1. It is a less expensive mode of entering into international business.

2. There is no investment risk

3. Since the business in the foreign country is managed by the licensee/franchisee who is a local person, there are lower risks of business takeovers or government interventions.

4. Since licensee/franchisee is a local person, he has greater market knowledge and customer contacts. It helps the licensor/franchiser in successfully conducting its marketing operations.

Limitations:
(a) The licensee can start marketing an identical product under a slightly different brand name.

(b) Trade secrets may lose in the foreign markets.

(c) Conflicts often develop between the licensor/franchiser and licensee/franchisee oyer issues such as maintenance of accounts, payment of royalty, etc.

4. Joint Ventures:
Joint venture means establishing a firm that is jointly owned by two or more independent firms. It can be brought into existence in three major ways.

• Foreign investor buying an interest in a local firm.
• Local firm acquiring an interest in an existing foreign firm.
• Both the foreign and local entrepreneurs jointly forming a new enterprise

Advantages:

1. Since the local partner also contributes to the equity capital, the international firm has less financial burden to expand the business globally.
2. It helps to execute large projects requiring huge capital outlays and manpower.
3. The foreign business firm benefits from local partner’s knowledge of the host countries.
4. The foreign business firm shares cost and risks with local partner. So they can enter into foreign market very easily and without high risk.

Limitations:

1. Foreign firms entering into joint ventures share the technology and trade secrets with local firms. It leads to leakage of technology and secrets to others.
2. The dual ownership arrangement may lead to conflicts

5. Wholly Owned Subsidiaries:
The parent company (holding company) acquires full control over the foreign company by making 100% investment in its equity capital. It is called wholly owned subsidiaries. It can be established in either of the two ways. i.e.

• Setting up a new firm altogether to start operations in a foreign country
• Acquiring an existing firm in the foreign country

Advantages:

1. The parent firm is able to exercise full control over its operations in foreign countries.
2. It is not required to disclose its technology or trade secrets to others.

Limitations:

1. It is not suitable for small and medium size firms which do not have enough funds to invest abroad.
2. The parent company alone has to bear the entire losses.
3. It is subject to higher political risk.

Students can Download Chapter 10 Mechanical Properties of Fluids Notes, Plus One Physics Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Physics Notes Chapter 10 Mechanical Properties of Fluids

Summary
Introduction
Unlike a solid, a fluid has no definite shape. Fluid is that which can flow. Liquids and gases are fluids. A fluid has no definite shape. It assumes the shape of the container.
Difference between the liquids and gases:

• Liquid is incompressible, while a gas is compressible.
• Liquid has a free surface, while a gas no free surface.

Common properties of liquids and gases:

• Liquids and gases can flow
• Liquids and gases can exert pressure on the walls of the container.

Pressure
In fluids, the molecules are free to move. When they move, they collide with the walls of the container and exert a force on the walls. The force is acting normal to the surface. The force acting per unit area normal to the surface is called pressure.

ie; P = F/A. Its unit is N/m² or Pascal (Pa), Another common unit of pressure is atmosphere. The pressure exerted by the atmosphere at sea level is called the atmospheric pressure.
I atm = 1.0313 × 10⁵Pa
Properties of Fluid Pressure:

• The pressure will be equal at any point on the same horizontal level of a liquid at rest.
• The pressure will be the same in all directions at any point in a liquid at rest.

Question 1.
When a surface is immersed in a liquid, what is the direction of pressure on the surface?

Answer:
The direction of pressure is always normal to the surface.
Density:
The density r for a fluid of mass m occupying volume V

The density of water at 4°C (277k) is 1 × 10³kg m^-3
Relative density:
The relative density of a substance is the ratio of its density to the density of water at 4°C. The relative density of aluminium is 2.7. Its density is 2.7 × 10³kg m^-3.
1. Variation of pressure with Depth:

Consider a fluid at rest in a container. Consider a cylindrical element of fluid having base area ‘A’ and height ‘h’. Let P₁ and P₂ be pressures at points 1 and 2 respectively.
The force at top of cylindrical element F₁ = P₁A
This force is acting vertically down ward.
Similarly, the force at bottom F₂ = P₂A
This force is acting vertically upward.
∴ Total force acting on the cylindrical element of fluid = P₂A – P₁A
The fluid is at rest. Hence, Net force on the cylindrical element of fluid = Weight of cylindrical element of fluid.
ie.: (P₂ – P₁)A = mg
(P₂ – P₁)A = vρg (∴ m = ρv)
(P₂ – P₁)A = Ahρg (∴ v = Ah)
P₂ – P₁ = hρg _____(1)
The above equation shows that pressure difference depends on the vertical distance h between the points (1 and 2), density of the fluid, acceleration due to gravity.
Gauge Pressure:
If the point 1 is shifted to the top of fluid, P₁ may be replaced by atmospheric pressure ‘P_a’. Let pressure at bottom of cylindrical element be ‘P\ then from eq (1), we can write
P – P_a = hρg
P = P_a + hρg
The above equation shows that, the pressure P (below the surface of a liquid open to the atmosphere) is greater than atmospheric pressure by an amount rgh. The excess pressure (P – P_a) at depth h is called guage pressure.

Hydrostatic paradox:
Question 2.
In which points (see figure) pressure is maximum?

Answer:
The liquid pressure is the same at all points (A, B, C). Because all the points lie at same horizontal level. The pressure at A, B and C do not depend upon base area or shape of the container. This paradox is called hydrostatic paradox.

2.  Atmospheric pressure and Gauge pressure:
Atmospheric pressure:
The pressure exerted by the atmosphere at any point is due to the weight of air above that point. At sea level the atmospheric pressure is maximum and is taken as 1 atmosphere.
1 atm = 1.013 × 10⁵ Pa
Mercury Barometer:
Italian scientist Evangelista Torricelli (1608 -1647) devised a method for measuring atmospheric pressure. This device is known as mercury barometer.

A long glass tube closed at one end is filled with mercury. Then it is inverted in a mercury reservoir. The mercury level inside the tube falls up to a height 76 cm.

Consider two points A and B in the reservoir. Since the reservoir is open to the atmosphere, the pressure at,
P₀ = P_a (atmospheric pressure).
The pressure at B is P_B = Hrg
The points A and B lie at same level, hence
pressure at A = pressure at B
P_a = P_B
ie; P_a = Hrg
In the experiment, it is found that the mercury column in the barometer has a height of about 76 cm at sea level. 76 cm of mercury = 1 atm.
Different unit of pressure:
1 mm of mercury = 1 torr
1 torr= 133 Pa
1 bar= 10⁵ Pa
Open – Tube Manometer:

open-tube manometer is a useful instrument for measuring pressure differences. This device consists of a U shaped tube containing liquid of density r. One end is open to the atmosphere and other end is connected to the system whose pressure is to be measured.

The pressure ‘P’ at A is equal to the pressure at B.
ie: P = P_a + hρg
(or) P – P_a = hρg
P is called absolute pressure.

3. Hydraulic Machines:
Hydraulic machines are based on Pascal’s law. Examples of hydraulic machines:

• Hydraulic Lift
• Hydraulic press
• Hydraulic brake.

Pascal’s Law:
Whenever external pressure is applied on any part of a fluid contained in a vessel, it is transmitted undiminished and equally in all directions.

Hydraulic lift:

A hydraulic lift is used to lift heavy load. Consider a liquid enclosed in a vessel with two cylinders C₁ and C₂ attached as shown in the figure. The cylinders are provided with two pistons having areas A₁ and A₂ respectively.
If F₁ is the force exerted on the area A₁.
pressure P₁ = \(\frac{F_{1}}{A_{1}}\)
If F₂ is the force exerted on the area A₂,
pressure P₂ = \(\frac{F_{2}}{A_{2}}\)
According to pascal’s law P₁ = P₂ ie;

Using this method we can lift heavy load by applying small force.
Hydraulic Brake:

Hydraulic brake is based on Pascals law. When the brake pedal (F) is pressed, a pressure is produced on liquid. This pressure will reach at A₁ and A₂. Due to large area of A₁ and A₂, a large force is produced. This large force will push brake shoes (S₁ ans S₂) in to the inner rim of wheel. Hence the motion of wheel will be retarded.

Streamline Flow
Fluid dynamics:
The study of the fluids in motion is known as fluid dynamics.
Steady Flow:
The flow of the fluid is said to be steady if at any given point, the velocity of each fluid particle remains constant in time. The path taken by a fluid particle under a steady flow is a streamline.
Turbulent flow:
As the speed of flow increase, at a certain speed the stream line flow stops and irregular flow starts. This irregular flow is called turbulent.

The speed at which the turbulent flow starts is called critical speed.
Equation of continuity:
Flow rate of a incompressible fluid is constant
ie Av = cont.
Where A is the area of cross section of flow and v is the velocity of flow. ‘Av’ is also called volume flux.
Proof:
Consider a flow of incompressible liquid. Let P, R and Q be three points of a flow. Consider three planes perpendicular to direction of flow at P, R and Q.

Let A_P, A_R and A_Q be the area of cross section and V_P, V_R and V_Q be the corresponding speeds at P, R, Q respectively.
The mass of liquid passing through area A_P in a time Dt, M_P = A_P V_P r_P ∆t
Similarly, M_R = A_R V_R r_R ∆t
M_Q = A_Q V_Q r_Q ∆t
But we know r_P = r_R = r_Q = r
Hence we get M_P = A_P V_P r ∆t
M_R = A_R V_Rr ∆t
M_Q = A_Q V_Q r ∆t
the mass of liquid flowing out = the mass flowing in
ie; M_P = M_R = M_Q
∴ A_PV_P = A_RV_R = A_QV_Q

Bernoulli’S Principle
Bernoulli’s theorem:
As we move along a streamline the sum of the pressure (p), the kinetic energy per unit volume \(\frac{\rho v^{2}}{2}\) and the potential energy per unit volume (ρgh) remains a constant.

(OR)

The total energy of an incompressible non-viscous liquid flowing from one place to another without friction is a constant. Mathematically Bernoulli’s theorem can be written as

Proof:

Consider an incompressible liquid flowing through a tube of non uniform cross section from region 1 to region 2. Let P₁ be the pressure, A₁ the area of cross section and V₁ the speed of flow at the region 1.

The corresponding values at region 2 are P₂, A_2, and V₂ respectively. Region 1 is at a height h₁ and region 2 is at a height h₂.
The workdone on the liquid in a time ∆t at the region 1 is given by
W₁ = force × distance
= P₁A₁∆ x₁
= P₁∆V₁ (∵ A₁∆x₁ = ∆V)
Where ∆x₁ is the displacement produced at region 1, during the time interval ∆t.
Similarly, the workdone in a time ∆t at the region 2 is given by,
W₂ = -P₂ A₂ ∆ x₂
W₂ = -P₂ ∆ V₂
[Here -ve sign appears as the direction of \(\vec{p}\) and ∆x are in opposite directions.]
Net workdone
DW = P₁ ∆ V₁ – P₂ ∆ V₂

According the equation of continuity
∆V₁ = ∆V₂ = ∆V
∆W= P₁ ∆ V – P₂ ∆ V
∆W = (P₁ – P₂) ∆ V _____(1)
This work done changes the kinetic energy, pressure energy and potential energy of the fluid.
If ∆m is the mass of liquid passing through the pipe in a time ∆t. the change in Kinetic energy is

Change in gravitational potential energy is given by
∆p.E = ∆mgh₂ – ∆mgh₁
∆p.E = ∆mg(h₂ – h₁) ______(3)
According to work-energy theorem work done is equal to the change in kinetic energy plus the change in potential energy.
ie; ∆w = ∆kE + ∆PE ______(4)
Substituting eq. 1, 2 and 3 in eq. 4, we get

Dividing by ∆V , we get

Case – 1
When the fluid at rest, its velocity is zero everywhere. Hence Bernoullis equation becomes
p₁ + ρgh₁ = P₂ + ρgh₂
(P₁ – P₂) = ρg(h₂ – h₁ )
Note: Bernoullis law is conservation law of energy for a flowing liquid.

1. Speed of Afflux: Torricellis law:
Torricellis law may be stated as the velocity of afflux through a hole at a depth ‘h’ will be equal to the velocity gained by a freely falling body when it travels a distance ‘h’. ie; v = \(\sqrt{2 \mathrm{gh}}\).
Proof
Consider a tank containing a liquid of density r with a small hole in its side. Let Y₁ be the height of the hole, and y₂ be height of water in the tank. Applying Bernoullis equation at points (1) and (2) we get

(∵ P₁ = P_a, the atmospheric pressure).
If the cross sectional area of the tank A₂ is much larger than that of the hole (ie; A₂ >> A₁ ), we take
v₂ ≈ 0.
∴ eq(1) can be written as.

Note: The equation (2) shows that the speed of afflux is determined by the container pressure. Such a situation occurs in rocket propulsion.

2. Venturi – meter:

A venturimeter is used to measure the flow of a liquid. It is based on Bernoullis theorem. Venturimeter consists of a horizontal tube of nonuniform cross section. A manometer (U tube) is attached to it as shown in the figure.

When a liquid flows through the tube, the manometer level falls in the limb (1) and rises in the limb (2). Let ‘h’ be the height difference of the manometer liquid in the two limbs. Let A be the cross-sectional area and V₁ the velocity at the wide limb(1) and V₂ be the corresponding values at the narrow limb (2).
According to Bernoullis theorem

Where ρ_m is the density of manometer liquid.

Using the above equation, the rate of flow can be measured.
Atomiser (application of Bernoulli’s theorem):

Atomiser is used for getting a fine spray of perfumer or insecticide. It consists of a cylinder with a piston. A small vessel containing liquid to be sprayed is attached to the cylinder. When the piston is moved forward air is blown out through a small opening of the cylinder.

As the velocity of flow of air increases, the pressure at the opening decreases. Due to the lower pressure at the opening, the liquid rises through the narrow tube and gets sprayed out along with air.

Blood flow and heart attack:
Bernoulli’s principle helps in explaining blood flow in artery. The artery may get constricted due to the accumulation of plaque on its inner walls. The speed of blood flow increases at which plaque is deposited. The increase in speed will lowers the pressure inside the artery and it may collapse due to the external pressure. This may result in heart attack.

4. Dynamic lift:
Dynamic lift is the force that acts on a body by virtue of its motion through a fluid (air). (This dynamic lift can be partly explained on the basis of Bernoulli’s principle)
Example:

1. Ball moving without spin
2. Ball moving with spin
3. Aerofoil or lift on aircraft wing.

1. Ball moving without spin:

When a ball move in air without spinning, the velocity of fluid (air) above and below the ball is the same. Hence pressure difference between above and below is zero. Therefore there is no upward or downward force on the ball.

2. Ball moving with spin:

When a ball is thrown in a air with spin, air will be dragged along with it. Therefore the velocity of air above (larger) and below (smaller) are different. This difference in the velocities of air results in the pressure difference between the lower and upper faces and there is a net upward force on the ball. This dynamic lift due to spinning is called Magnus effect.

3. Aerofoil or lift on aircraft wing:

An aerofoil is a solid piece, shaped to provide an upward vertical force as it moves horizontally through air. Due to the curved shape at the top, the velocity of the air on the top side increases. Due to increase in velocity, the pressure at this region decreases. Thus an upward force develops on the aerofoil. This principle is applied in the design of the wings of aeroplanes.

Viscosity
Viscosity is liquid friction. When liquid layer moves over another liquid layer, there is a force of friction between the liquid layers, opposing the motion of layers.

Laminar flow:
When a liquid flows on a surface, the layer of liquid in contact with the surface will be rest. The velocity of the layer increases as the distance of the layer from the surface increases. The velocity is maximum on the top most layer. This type of flow is known as laminar.

Coefficient of viscosity:
The coefficient of viscosity for a fluid is defined as the ratio of shearing stress to the strain rate. Explanation:

Consider a portion of liquid having shape ABCD. When this liquid flows, it take the shape AEFD after a short interval of time Dt
During this time interval the liquid has undergone a shear strain of \(\frac{\Delta \mathbf{x}}{\ell}\). Since, the stress in a flowing fluid increases with time, we take rate.
ie. strain rate = \(\frac{\Delta \mathbf{x}}{\ell \Delta t}\)

Unit of viscosity:
The SI unit of viscosity is poiseiulle (PI). Its another units are NSm^-2 or PaS.
Note:

• Blood is thicker (more viscous) than water. The relative viscocity (n/n_water) of blood remains constant between 0° C and 37° C.
• The viscocity of liquid decreases with temperature while it increases in the case of gases.

1. Stokes law:
If a body is moving through a fluid, its velocity is influenced by the viscosity of the medium. Consider a small sphere of radius ‘a’ falling under gravity in air: The viscocity of air opposes the motion of the sphere. This opposing force is called viscous force and can be written as.
F = 6πaηv
This is called stokes, formula.
Where η is the coefficient of viscocity of the medium and v is the velocity of the body.

(i) Terminal velocity:
The constant velocity attained by a body as it falls down through a fluid medium is called the terminal velocity.
Expression for terminal velocity:
Considers sphere of radius ‘a’ densitity r falling through a liquid of density s and viscocity h. The viscous force acting on the sphere can be written as
F = 6πaηv
Where v is the velocity of sphere. This force is acting in upward direction. When the body comes down its velocity will increase. Hence the viscous force will also increases.

When the viscous force is equal to the weight of the body in the medium. The net force on the body is zero. Now the body falls without acceleration. It moves with a constant velocity called the terminal velocity.
The weight of a body in a medium,

When body has terminal velocity, we can write.

Reynolds Number
The turbulence in a fluid is determined by a dimension parameter called Reynolds number.
Reynolds number R_e = \(\frac{\rho \mathbf{v d}}{\eta}\)
Where ‘r is the density of a fluid, V- the speed of flow of the liquid, ‘d’- the dimension of pipe, h- viscocity of the liquid. R_e – the dimensionless number. The flow is streamline when the R_e is below 1000, unsteady when R_e is in between 1000 and 2000 and turbulent when R_e > 2000.
Critical velocity:
The maximum velocity of a fluid in a tube for which the flow remains streamlined is called its critical velocity.
Critical velocity v = \(\frac{R_{e} \eta}{\rho d}\).

Surface Tension
Liquids acquire a free surface when poured in a container. These surfaces possess some additional. energy. This phenomenon is known as surface tension.

1. Surface Energy:
Question 4.
What is the reason for surface tension?

Answer:
Consider a liquid enclosed in a vessel as shown in figure. Let A, B, and C be three molecules in the liquid. For a molecule A, the forces of attraction on the molecule are equal in all directions. Hence net force on it is zero. Consider a molecule B near the surface. In this case the molecule is partially outside the liquid. So there is a net downward force.

Consider another molecule Con the surface of liquid. Half of the sphere is outside the liquid. Hence the downward force on molecule is maximum. This, when a molecule comes to the surface, it is doing work to overcome this downward pull. The work done resides as RE. in the molecule on the surface. Thus molecule on the surface of liquid have P.E. This energy is called the surface energy.
Note:
1. To increase the area of surface of a liquid, work has to be done. This energy is required to increase the surface area.

2. Surface energy and surface tension:
Question 5.
Show that Surface tension is equal to surface energy per unit area.

Answer:
Consider a horizontal liquid film as shown in figure. The bar at one end of film is free to move. Move the bar a small distance as shown in figure. Since the area of the surface increases, some work has to be done against an internal force.
workdone W = Fd _____(1)
This workdone is stored as additional energy in the film. If the surface energy of the film is S per unit area, the workdone to increase the surface area.
W = S × increase in area
W = S × 2/d ______(2)
Where 2/d is the increase in area due to two sides of film.
equating eq(1) and eq(2),we get
S 2/d = Fd

This quantity S is the magnitude of surface tension. It is equal to the surface energy per unit area.

3. Angle of contact:
Angle of contact is the angle between the solid surface and the tangent drawn to the liquid surface at the point of contact inside the liquid.

If angle of contact of liquid is acute(<90°), the meniscus in the tube will be concave. The liquid level in the tube will rise to a certain height. This is called capillary rise. If the angle of contact is obtuse (>90°), the liquid level falls in the tube. This is called capillary fall or capillary depression.

4. Drops and bubbles:
Due to surface tension, the liquid surface always tends to have the minimum surface area. For a given volume, a sphere has a minimum surface area. Hence, srnail drops and bubbles of a liquid assume spherical shape.

On the other hand, for bigger drops the effect of gravity predominates over surface tension and the drop gets flattened.

(i) Excess of pressure inside a spherical drop The molecules near the surface of a drop experience a resultant pull inwards due to surface tension. Because of this inward pull, the pressure inside is greater than the outside.

Due to the forces of surface tension, the drop tends to contract. But due to excess inside pressure, the drop tends to expand. When the drop is in equilibrium, these two forces will be equal and opposite.

Expression for excess pressure inside a liquid-drop:

Consider a drop of liquid of radius r. Let p_i and p_o be the values of pressure inside and outside the drop. Let the radius of liquid of drop increases by a small amount Dr under the pressure difference.
The outward force acting on the surface of the drop,
f = pressure difference × surface area,
ie. f = (p_i – p_o)4pr²
If the radius of liquid drop is increased by Dr due to the above force
The work done (DW) = f.Dr
= (p_i – p_o)4pr²Dr _____(1)
The increase in surface area of the drop
= 4p(r + Dr)² – 4pr²
= 4p(r² + 2rDr + Dr²) – 4pr² = 8prDr [ Neglecting Dr²]
If S is the surface tension of the liquid, the work done to increase the surface area,
DW = Increase in surface area × surface tension
DW= 8prDr.S _____(2)
From equation (1) and (2), we get 2S
p_i – p_o = \(\frac{2 \mathrm{S}}{\mathrm{r}}\).

(ii) Expression for excess pressure inside a spherical bubble:
A liquid bubble has air both inside and outside it. Hence, it has two surfaces;
Hence the total increase in the surface area, = 16prDr
The workdone to increase the surface area,
= 16prDrS ______(3)
From equation (1) and (3) we get,
p_i – p_o = \(\frac{4 \mathrm{S}}{\mathrm{r}}\)

5. Capillary rise:
A tube of very fine core is called a capillary tube. When a capillary tube is dipped in a liquid, the liquid immediately rises in the tube. This phenomena is called capillarity or capillary rise. In the case of mercury, capillary depression is observed.
Expression for capillary rise:

Consider a capillary tube of radius ‘a’ dipped in a liquid of density rand surface tension S. If the liquid has a concave meniscus it will rise in the capillary tube. Let h be the rise of the liquid in the tube. Let p₁ be the pressure on the concave Side of the meniscus and p₀, that on the other side.
The excess pressure on the concave side of the meniscus can be written as
p_i – p_o = \(\frac{2 \mathrm{S}}{\mathrm{r}}\) _____(1)
Where R is the radius of the concave meniscus. The tangent to the meniscus at the point A makes an angle q with the wall of the tube.
In the right angled triangle ACO

substituting the values of R in the equation (1)

Considering two points M and N in the same horizontal level of a liquid at rest,
pressure at N = pressure at M
But pressure at M = p_i, the pressure over the concave meniscus and pressure at N = p_o + hrg
∴ p_o = p_o + hrg
or p_i – p_o = hrg ______(3)
From equations (2) and (3), we get
hρg = \(\frac{2 \mathrm{S} \cos \theta}{\mathrm{a}}\)

case-1
For water q = 0, ie. cosq = 1
hence S = \(\frac{1}{2}\) haρg

6. Detergents and Surface Tension:
Dirty clothes containing grease and oil stains sticking on them cannot be cleaned by soaking them in water. – This is because water will not wet greasy dirt. If water could wet grease, then the flow of water would carry away some greasy dirt.

But, by adding detergent or soap to water, the greasy dirt can be removed. The molecules of the detergent are hairpin shaped. When the detergent is added to water, one end of hair pin shaped molecule get attached to the water surface and other end to stain.

This results in the formation of water – grease interface. Thus surface tension between water and grease reduces. Hence dirt can be removed by the moving water.

Students can Download Chapter 13 Hydrocarbons Notes, Plus One Chemistry Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Chemistry Notes Chapter 13 Hydrocarbons

Introduction
The compounds formed by carbon and hydrogen are called Hydrocarbons.

Classification
Hydrocarbons are broadly classified into two main classes. Open chain hydrocarbons and closed chain or cyclic hydrocarbons.

Open chain hydrocarbons are hydrocarbons containing open chain of carbon atoms in their molecules. The chain may be straight or branched. These compounds are also called aliphatic hydrocarbons. They are further divided into three classes: Alkanes, alkenes, and alkynes.

Closed chain or cyclic hydrocarbons are hydrocarbons having closed chains or righs in their molecules. They are further divided into two categories: Alicyclic hydrocarbons and aromatic hydrocarbons. Alicyclic hydrocarbons contain ring or closed chain of carbon atoms, but resemble aliphatic compounds in most of their properties. Aromatic hydrocarbons contain at least one benzene ring which is a hexagonal ring of carbon atoms with three double bonds in alternate positions.

ALkanes
Alkanes are saturated aliphatic hydrocarbons containing only carbon-carbon single bonds in their molecules. They can be represented by the general formula c_n H_2n+2 Where n may have values 1, 2, 3, ………… Since they are relatively inert towards most of the common reagents, they are called paraffins (Latin : parum = Little, affinis = affinity)

Nomenclature
Nomenclature of alkanes has already been discussed in Unit =12 ‘

Preparation:
Petroleum and natural gas are the main sources of alkanes. However, alkanes can be prepared by following methods:
1. From unsaturated hydrocarbons
Dihydrogen gas adds to alkenes and alkynes in the presence of finely divided catalysts like platinum, palladium or nickel to form alkanes. This process is called hydrogenation. These metals adsorb dihydrogen gas on their surfaces and activate the hydrogen – hydrogen bond.

Platinum and palladium catalyse the reaction at room temperature but higher temperature and pressure are required.

2. From alkyl halides
i) Alkyl halides (except fluorides) on reduction with zinc and dilute hydrochloric acid give alkanes.

ii) Alkyl halides on treatment with sodium metal in dry ether (free from moisture) solution give higher alkanes. This reaction is known as Wurtz reaction and is used for the preparation of higher alkanes containing even number of carbon atoms.

3. From carboxylic acids
i) Sodium salts of carboxylic acids on heating with soda lime (mixture of sodium hydroxide and calcium oxide) give alkanes containing one carbon atom less than the carboxylic acid. This process of elimination of carbon dioxide from a carboxylic acid is known as Decarboxylation.

Sodium ethanoate

ii) Kolbe’s electrolytic method:
An aqueous solution of sodium or potassium salt of a carboxylic acid on electrolysis gives alkane containing even number of carbon atoms at the anode.
2CH₃COO^–Na⁺ +2H₂O
Sodium acetate
-Electrolysis
CH₃ – CH₃ +2CO₂ +H₂ +2NaOH
The reaction is supposed to follow the following path:

Methane cannot be prepared by this method.

Properties
Physical properties:
Alkanes are almost non-polar molecules because of the covalent nature of C-C and C-H bonds and due to very little difference of electronegativity between carbon and hydrogen atoms. They possess weak van der Waals’ forces. Due to the weak forces, the first four members, C₁ to C₄ are gases, C₅ to C₁₇ are liquids and those containing 18 carbon atoms or more are solids at 298 K. It is generally observed that in relation to solubility of substances in solvents, polar substances are soluble in polar solvents, whereas the non-polar ones in non-polar solvents i.e., like dissolves like. There is a steady increase in boiling point with increase in molecular mass.

Chemical properties
As already mentioned, alkanes are generally inert towards acids, bases, oxidising and reducing agents. However, they undergo the following reactions under certain conditions.

1. Substitution reactions
One or more hydrogen atoms of alkanes can be replaced by halogens, nitro group, and sulphonic acid group. Halogenation takes place either at higher temperature (573-773 K) or in the presence of diffused sunlight or .ultraviolet light. Lower alkanes do not undergo nitration and sulphonation reactions. These reactions in which hydrogen atoms of alkanes are substituted are known as substitution reactions. As an example,chlorination of methane is given below:

Halogenation

It is found that the rate of reaction of alkanes with halogens is F₂ > Cl₂ > Br₂ > l₂. Rate of replacement of hydrogens of alkanes is :3° > 2° > 1 °. Fluorination is too violent to be controlled, lodination is very slow and a reversible reaction. It can be carried out in the presence of oxidizing agents like HIO₃ or HNO₃.
CH₄ +I₂ \(\rightleftharpoons \) CH₃I+HI
HIO₃ +5HI → 3l₂ +3H₂O
Halogenation is supposed to proceed via free radical chain mechanism involving three steps namely initiation, propagation, and termination as given below:

Mechanism
i) Initiation :
The reaction is initiated by homolysis of chlorine molecule in the presence of light or heat. The Cl-Cl bond isweakerthantheC-C and C-H bond and hence is easiest to break.

ii) Propagation:
It involves the following steps

Two such steps given below explain how more highly halogenated products are formed.

iii) Termination :
The reaction stops after some time due to consumption of reactants and / or due to the following side reactions:
The possible chain terminating steps are :

Though in (c), CH₃-Cl, the one of the products is formed but free radicals are consumed and the chain is terminated. The above mechanism helps us to understand the reason for the formation of ethane as a byproduct during chlorination of methane.

2. Combustion

3. Controlled oxidation

iv) Ordinarily alkanes resist oxidation but alkanes having tertiary H atom can be oxidized to corresponding alcohols by potassium permanganate.

4. Isomerisation
n-Alkanes on heating in the presence of anhydrous aluminum chloride and hydrogen chloride gas isomerise to branched-chain alkanes. Major products are given below. Minor products are generally not reported in organic reactions.

5. Aromatization
n-Alkanes having six or more carbon atoms on heating to 773 K at 10-20 atmospheric pressure in the presence of oxides of vanadium, molybdenum or chromium supported over alumina get dehydrogenated and cyclised to benzene and its homologues. This reaction is known as aromatization or reforming.

6. Reaction with steam

7. Pyrolysis
Higher alkanes on heating to higher temperature decompose into lower alkanes, alkenes etc. Such a decomposition reaction into smaller fragments by the application of heat is called pyrolysis or cracking.

Preparation of oil gas or petrol gas from kerosene oil or petrol involves the principle of pyrolysis.

Conformations
The C-C bonds in alkanes are sigma bonds. Carbon atoms connected through sigma bonds in alkanes can undergo rotation about the bond axis. As a result of this rotation, a large number of different spatial arrangements of atoms of groups attached to the carbon atoms are possible. These different spatial arrangements are called conformations. Thus, the different spatial arrangements of atoms in a molecule which arise due to free rotation about carbon-carbon single bond are called conformations.

Conformations of ethene:
Ethane molecule (C₂H₆) contains a carbon-carbon single bond with each carbon atom attached to three hydrogen atoms. Considering the ball and stick model of ethane, keep one carbon atom stationary and rotate the other carbon atom around the C-C axis. This rotation results into infinite number of spatial arrangements of hydrogen atoms attached to one carbon atom with respect to the hydrogen atoms attached to the other carbon atom. These are called conformational isomers (conformers). There are two extreme cases. One such confirmation in which hydrogen atoms attached to two carbons are as closed together as possible is called eclipsed conformation and the other in which hydrogens are as far apart as possible is known as the staggered conformation. Any other intermediate conformation is called a skew conformation. lt may be remembered that in all the conformations, the bond angles and the bond lengths remain the same. Eclipsed and the staggered conformations can be represented by Sawhorse and Newman projections.

1. Sawhorse projection
C-C bond is represented by straight line. Upper end of the line is slightly tilted. The front carbon is shown by the lower end of the line and the rear carbon is represented by upper end. The angle between C-H bonds is 120°. Sawhorse projections of eclipsed and staggered conformations are depicted below.

2. Newman projections
In this projection, the molecule is viewed at the C-C bond head on. The carbon atom nearer to the eye is represented by a point. Three hydrogen atoms attached to the front carbon atom are shown by three lines drawn at an angle of 120° to each other. The rear carbon atom (the carbon atom away from the eye) is represented by a circle and the three hydrogen atoms are shown attached to it by the shorter lines drawn at an angle of 120° to each other.

Relative stability of conformations:
As mentioned earlier, in staggered form of ethane, the electron clouds of carbon-hydrogen bonds are as far apart as possible. Thus, there are minimum repulsive forces, minimum energy and maximum stability of the molecule. On the other hand, when the staggered form changes into the eclipsed form, the electron clouds of the carbon-hydrogen bonds come closer to each other resulting in increase in electron cloud repulsions. To check the increased repulsive forces, molecule will have to possess more energy and thus has lesser stability. As already mentioned, the repulsive interaction between the electron clouds, which affects stability of a conformation, is called torsional strain.

Magnitude of torsional strain depends upon the angle of rotation about C-C bond. This angle is also called dihedral angle or torsional angle. Of all the conformations of ethane, the staggered form has the least torsional strain and the eclipsed form, the maximum torsional strain. Thus it may be inferred that rotation around C-C bond in ethane is not completely free. The energy difference between the two extreme forms is of the order of is very small.

Alkenes
Alkenes are unsaturated hydrocarbons containing a carbon-carbon double bond. Acyclic alkenes with one double bond have the general formula C_nH_2n. Thus they are isomeric with cycloalkanes. They are also known as olefins (Greek word olefiant = oil forming) because the lower members of this family form oily products when treated with chlorine.

We have already seen that a carbon-carbon double bond consists of a sigma bond and a pi-bond. A pi-bond is weaker than a sigma – bond because sidewise overlapping takes place to smaller extent. It should be noted that a double bond is shorter than a single bond. Again, the C-H bond length in ethene is slightly shorter than that in alkanes because it is formed by the overlap of sp² hybrid orbitals of carbon.

Isomerism in Alkenes
Alkenes show chain isomerism, position isomerism and geometrical isomerism,
i) Chain Isomerism :
The simplest alkene which can exhibit isomerism is butene (C₄ H₈). It exists as two chain isomers.

ii) Position isomerism :
Position isomers of alkenes differ in the position of double bond.

iii) Geometrical isomerism :
The isomers which have the same structural formula but differ in spatial arangement of atoms or groups about the double bond are called geometrical isomers and the phenomenon is known as geometrical isomers of but 2 ene are given below.

The geometrical isomer with similar groups on the same side of the double bond is called the cis isomer while the other isomer with similar groups on opposite side is called the trans isomer. Because of this reason geometrical isomerism is also called cistrans isomerism.

Hindered rotation about carbon-carbon double bond is responsible for the existence of geometrical isomers. As we know, C=C consists of a sigma bond and a pi bond. Due to the presence of pi bond, the groups or atoms attached to doubly bonded carbon atoms cannot rotate about it. They can do so only by breaking the pi-electron cloud.

Preparation
1) From alkynes:
Partially deactivated palladised charcoal is known as Lindlar’s catalyst is used Alkenes thus obtained are having cis geometry. However, alkynes on reduction with sodium in liquid ammonia form trans alkenes.

2) From alkyl halides:
Alkyl halides (R-X)on heating with alcoholic potash eliminate one molecule of halogen acid to form alkenes. This reaction is known as dehydrohalogenation i.e., removal of halogen acid. This is example of β-elimination reaction, since hydrogen atom is eliminated from the β-carbon atom(carbon atom next to the carbon to which halogen is attached).

It is observed that for halogens, the rate is:iodine > bromine > chlorine, while for alkyl groups it is: tert > secondary > primary.

3) From vicinal dihalides :
Dihalides in which two halogen atoms are attached to two adjacent carbon atoms are known as vicinal dihalides. Vicinal dihalides on treatment with zinc metal lose a molecule of ZnX₂ form an alkene. This reaction is known as dehalogenation.
CH₂Br – CH₂Br + Zn CH₂ = CH₂ + ZnBr₂

4) From alcohols by acidic dehydration:
Alcohols on heating with concentrated sulphuric acid form alkenes with the elimination of one water molecule. Since a water molecule is eliminated from the alcohol molecule in the presence of an acid, this reaction is known as acidic dehydration of alcohols. This reaction is also the example of β-elimination reaction since-OH group takes out one hydrogen atom from the β-carbon atom.

Chemical Properties
1) Addition of dihydrogen:
Alkenes add up one molecule of dihydrogen gas in the presence of finely divided nickel, palladium or platinum to form alkanes

2) Addition of halogens :

3) Addition of hydrogen halides:
Hydrogen halides (HCl, HBr,HI) add up to alkenes to form alkyl halides. The order of reactivity of the hydrogen halides is HI > HBr> HCI. Like addition of halogens to alkenes, addition of hydrogen halides is also an example of electrophilic addition reaction. Addition reaction of HBr to symmetrical alkenes Addition reactions of HBr to symmetrical alkenes (similar groups attached to double bond) take place by electrophilic addition mechanism.

Addition reaction of HBr to unsymmetrical alkenes (Markovnikov Rule)
There are two possible products in the following reaction

Markovnikov, a Russian chemist made generalisations about such reactions. It to frame a rule called Markovnikov rule. The rule states that negative part of the addendum (adding molecule) gets attached to that carbon atom which possesses lesser number of hydrogen atoms. Thus according to this rule, product I i.e., 2- bromopropane is expected. In actual practice, this is the principal product of the reaction.

Anti Markovnikov addition or peroxide effect or Kharash effect
In the presence of peroxide, addition of HBr to unsymmetrical alkenes like propene takes place contrary to the Markovnikov rule. This happens only with HBr but not with HCI and HI. This addition reaction was observed by M.S. Kharash and F.R. Mayo in 1933. This reaction is known as peroxide or Kharash effect or addition reaction anti to Markovnikov rule.

4) Addition of sulphuric acid:
Cold concentrated sulphuric acid adds to alkenes in accordance with Markovnikov rule to form alkyl hydrogen sulphate by the electrophilic addition reaction.

5) Addition of water :
In the presence of a few drops of concentrated sulphuric acid alkenes react with water to form alcohols, in accordance with the Markovnikov rule.

6) Oxidation:
Alkenes on reaction with cold,dilute, aqueous solution of potassium permanganate (Baeyer’s reagent) produce vicinal glycols. Decolorisation of KMnO. solution is used as a test for unsaturation.

b) Acidic potassium permanganate or acidic potassium dichromate oxidises alkenes to ketones and/or acids depending upon the nature of the alkene and the experimental conditions.

7) Ozonolysis:
Ozonolysis of alkenes involves the addition of ozone molecule to alkene to form ozonide, and then cleavage of the ozonide by Zn- H20 to smaller molecules. This reaction is highly useful in detecting the position of the double bond in alkenes or other unsaturated compounds.

8) Polymerisation:
You are familiar with polythene bags and polythene sheets. Polythene is obtained by the combination of large number of ethene molecules at high temperature, high pressure and in the presence of a catalyst. The large molecules thus obtained are called polymers. This reaction is known as polymerisation. The simple compounds from which polymers are made are called monomers. Other alkenes also undergo polymerisation.

Alkynes
Like alkenes, alkynes are also unsaturated hydrocarbons. They contain at least one triple bond between two carbon atoms. The number of hydrogen atoms is still less in alkynes as compared to alkenes or alkanes. Their general formula is C_nH_2n-2 Alkynes show chain isomerism and position isomerism.

i) Chain isomerism :
Alkynes having five or more carbon atoms show chain isomerism due to different structures of the carbon chain. For example, the chain isomers of C₅H₈ are

ii) Position isomerism:
Butyne and higher alkynes show position isomerism. For example, the position isomers of butyne are

Structure Of Triple Bond
Each carbon atom of ethyne has two sp hybridised orbitals. Carbon-carbon sigma (σ)bond is obtained by the head-on overlapping of the two sp hybridised orbitals of the two carbon atoms. The remaining sp hybridised orbital of each carbon atom undergoes overlapping along the internuclear axis with the 1s orbital of each of the two hydrogen atoms forming two C-H sigma bonds. H-C-C bond angle is of 180°. Each carbon has two unhybridised p orbitals which are perpendicular to each other as well as to the plane of the C-C sigma bond. The 2p orbitals of one carbon atom are parallel to the 2p orbitals of the other carbon atom, which undergo lateral or sideways overlapping to form two pi (π) bonds between two carbon atoms. Thus ethyne molecule consists of one C-C σ bond, two C-H σ bonds, and two C-C π bonds. The strength of C ≡ C bond is more than those of C=C bond and C-C bond.

Preparation
1. From calcium carbide:

2. From vicinal dihalides:

Properties

Physical properties
Physical properties of alkynes follow the same trend of alkenes and alkanes. First three members are gases, the next eight are liquids and the higher ones are solids. All alkynes are colourless. Ethyene has characteristic odour. Other members are odourless. Alkynes are weakly polar in nature. They are lighter than water and immiscible with water but soluble in organic solvents like ethers, carbon tetrachloride, and benzene. Their melting point, boiling point and density increase with increase in molar mass.

Chemical Properties
Acidic Character Of Alkyne

A. Acidic character of alkyne:
The acidic character of acetylene and other l-alkynes can be explaned on the basis of the sp hybridisation state of the triply bonded carbon atom. We know that an electron in s-orbital is more tightly held than that in a p-orbital because s-electrons are more close to the nucleus. Now, sp hybridised orbital has greater s-character (50%) as compared to sp² (33%) and sp³ (25%) hybrid orbitals. Due to large s-character, the electrons in sp hybridised orbitals are held more tightly by the nucleus. Thus, sp hybridised carbon is more electronegative than sp² or sp³ hybridised carbon atoms. Due to this, the hydrogen atom attached to sp hybridised carbon atom develops slight positive charge and is acidic in character.

B. Addition reactions:

The addition product formed depends upon stability of vinylic cation. Addition in unsymmetrical alkynes takes place according to Markovnikov rule. Majority of the reactions of alkynes are the examples of electrophilic addition reactions. A few addition reactions are given below:
(i) Addition of dihydrogen

(ii) Addition od halogens

(iii) Addition of hydrogen halides :
Two molecules of hydrogen halides (HCl, HBr,HI) add to alkynes to form gem dihalides (in which two halogens are attached to the same carbon atom)

(iv) Addition of water:

(v) Polymerisation
(a) Linear polymerisation:
Under suitable conditions, linear polymerisation of ethyne takes place to produce polyacetylene or polyethyne which is a high molecularweight polyene containing repeating units . of (CH = CH – CH = CH) and can be represented as —(CH = CH – CH = CH)_n — Under special conditions, this polymer conducts electricity.

Thin-film of polyacetylene can be used as electrodes in batteries. These films are good conductors, lighter and cheaper than the metal conductors.

(b) Cyclic polymerisation:

Aromatic Hydrocarbons
Aromatic compounds are a class of compounds having characteristic stability in spite of having double bonds in their structure. Simple aromatic compounds contain one or more benzene rings. They are known as benzenoid aromatic compounds. There is yet another series of compound which exhibit aromatic properties but lack benzene like structures. They are called non-benzenoid aromatic compounds. Heterocyclic compounds such as pyrrole, thiophene etc. are simple examples of non-benzenoid aromatic compounds. Structures of some simple arenes (benzenoid) are given below.

Resonance and stability of benzene
According to resonance theory, benzene is a resonance hybrid of the two Kekule structures I & II shown below.

These two structures I & II are known as canonical structures of benzene. The actual structure of benzene is intermediate between the two Kekule structures and is referred to as the resonance hybrid. As a result of resonance, all carbon-carbon bond lengths in benzene become equal and lie in between C=C and C-C bond length.

Further, a resonance hybrid will always be more stable than any of the contributing (or canonical) structures. Thus the actual molecule of benzene is more stable than either of the two Kekule structures. The difference between the energy of the most stable contributing structure and the energy of the resonance hybrid is known as resonance energy. Resonance energy of benzene has been found to be about 150 kJ mol^-1.

Aromaticity
Benzene was considered as parent ‘aromatic’ compound. Now, the name is applied to all the ring systems whether or not having benzene ring, possessing following characteristics.
i) Planarity
ii) Complete delocalisation of the π electrons in the ring
iii) Presence of (4n + 2)π electrons in the ring where n is an integer (n = 0, 1,2,…).

This is often referred to as Hiickel Rule.
Some examples of aromatic compounds are given below:

Preparation of Benzene
Benzene is commercially isolated from coal tar. However, it may be prepared in the laboratory by the following methods.
i) Cyclic polymerisation of ethyne: (Section 13.4.4)
ii) Decarboxylation of aromatic acids:
Sodium salt of benzoic acid on heating with sodalime gives benzene.

iii) Reduction of Phenol

Properties

Physical Properties
Aromatic hydrocarbons are non- polar molecules and are usually colourless liquids or solids with a characteristic aroma. You are also familiar with naphthalene balls which are used in toilets and for preservation of clothes because of unique smell of the compound and the moth repellent property. Aromatic hydrocarbons are immiscible with water but are readily miscible with organic solvents. They bum with sooty flame.

Chemical properties
Arenes are characterised by electrophilic substitution reactions. However, under special conditions they can also undergo addition and oxidation reactions.

Electrophilic substitution reactions
The common electrophilic substitution reactions of arenes are nitration, halogenation, sulphonation, Friedel Craft’s alkylation and acylation reactions in which attacking reagent is an electrophile (E+)
i) Nitration:

ii) Halogenation:
Arenes react with halogens in the presence of a Lewis acid like anhydrous FeCl₃, FeBr₃ or AlCl₃ to yield haloarenes.

iii) Sulphonation:

iv) Friedel-Crafts alkylation reaction:

v) Friedel-Crafts acylation reaction:
The reaction of benzene with an acyl halide or acid anhydride in the presence of Lewis acids (AlCl₃) yields acyl benzene

If excess of electrophilic reagent is used, further substitution reaction may take place in which other hydrogen atoms of benzene ring may also be successively replaced by the electrophile. For example, benzene on treatment with excess of chlorine in the presence of anhydrous AlCl₃ in dark yields hexachlorobenzene (C₆Cl₆).

a) Generation of electrophile E^A :
During chlorination, alkylation and acylation of benzene, an-hydrous AlCl₃, being a Lewis acid helps in generation of the elctrophile Cl^⊕, R^⊕. RC^⊕O (acylium ion) respectively by combining with the attacking reagent.

In the case of nitration, the electrophile, nitronium ion, NO₂⁺ is produced by transfer of a proton (from sulphuric acid) to nitric acid in the following manner:

It is interesting to note that in the process of generation of nitronium ion, sulphuric acid serves as an acid and nitric acid as a base.
Thus, it is a simple acid-base equilibrium,

b) Formation of Carbocation (arenium ion):
Attack of electrophile results in the formation of σ – complex or arenium ion in which one of the carbon is sp³ hybridised and the arenium ion gets stabilised by resonance. Sigma complex or arenium ion loses its aromatic character because delocalisation of electrons stops at sp³ hybridised carbon.

The areneium ion gets stabilised by resonance:

c) Removal of proton:

Addition reactions

Combustion:

Directive Influence Of A Functional Group In Monosubstituted Benzene
In benzene all the six hydrogen atoms are equivalent. There fore, replacement of anyone hydrogen atom by a substituent gives a single monosubstituted derivative of benzene. However, when a monosubstituted product is converted into a disubstituted benzene derivative, three different isomers can be obtained. They are,

Carcinogenicity And Toxicity
Benzene and polynuclear hydrocarbons containing more than two benzene ring fused together are toxic and said to posses cancer producing (carcinogenic) property. They are formed due to the incomplete combustion of organic materials like tobacco, coal, and petroleum.