Class 8

You can Download जल-बैंक Questions and Answers, Summary, Activity, Notes, Kerala Syllabus 8th Standard Hindi Solutions Unit 4 Chapter 3 help you to revise complete Syllabus and score more marks in your examinations.

Kerala State Syllabus 8th Standard Hindi Solutions Unit 4 Chapter 3 जल-बैंक

जल-बैंक पाठ्यपुस्तक के प्रश्न और उत्तर

Jal Bank Hindi Story Kerala Syllabus 8th प्रश्ना 1.
‘चप्पे-चप्पे पर जल बैंक खुल गए हैं।’ लेखक की इस कल्पना के पीछे भविष्य का कौन-सा संकेत है?

उत्तर:
पानी की कमी एक गंभीर समस्या बनती जा रही है। अब भी हम इस दिशा पर ध्यान न रखेंगे तो भविष्य बड़ी आपत्ति हो जाएगी। पानी के लिए हमें किसी जल बैंक जैसी व्यवस्थाओं का आश्रय लेना पड़ेगा।

Hss Live Guru 8 Hindi Kerala Syllabus प्रश्ना 2.
‘पानी-पानी होना’, ‘पानीदार होना’ आदि प्रयोगों का मतलब क्या है?

उत्तर:
‘पानी-पानी होना’ का मतलब है- अत्यंत लज्जित होना और ‘पानीदार होना’ का मतलब होना- धनी होना।

Hss Live Guru Hindi 8th Kerala Syllabus प्रश्ना 3.
‘घर में पीने के वास्ते भी एक बूंद नहीं है’ लोग ऐसा झूठ क्यों कहते हैं?

उत्तर:
पानी की कमी बहुत है। लेकिन कुछ लोग उसके उपयोग में सावधानी नहीं बरते। कुछ लोग पानी के बिना तरसते हैं। उनके सामने लोग झूठ बोलते हैं कि पीने के लिए भी एक बूंद पानी नहीं है। यहाँ लोगों की संकुचित भाव की ओर संकेत है।

Hss Live Guru 8th Hindi Kerala Syllabus प्रश्ना 4.
‘चारों उँगलियाँ पानी में’ इस प्रयोग से आप क्या समझते हैं?

उत्तर:
‘चारों उँगलियाँ पानी में’ का मतलब है- जीवन में बड़ा नुकसान होना।

जल-बैंक Textbook Activities

Hsslive Guru Hindi Class 8 Kerala Syllabus प्रश्ना 1.
चर्चा करें।
जल बैंक की संकल्पना कैसी लगी?
वर्तमान समाज में इसकी प्रासंगिकता क्या है?

उत्तर:
जल दुर्लभता आज की विकट समस्या है। ऐसी स्थिति में जलबैंक की संकल्पना उचित है।

Hsslive Guru 8th Hindi Kerala Syllabus प्रश्ना 2.
जल-संरक्षण की आवश्यकता पर नारे बनाएँ।

जल है तो कल है।
जल जीवन का आधार।
जल नहीं तो हम नहीं।
जल ही जीवन है।
बूंद-बूंद का संरक्षण, जीवन का संरक्षण।
आज संजोएँ हरेक बूंद, कल को बनाएँ खूब सुहाना।

Hsslive Guru 8th Class Hindi Kerala Syllabus प्रश्ना 3.
उपर्युक्त नारों की मदद से पोस्टर तैयार करें।

जल-बैंक Summary in Malayalam and Translation

 जल-बैंक शब्दार्थ Word meanings

You can Download Basic Constituents of Matter Questions and Answers, Summary, Activity, Notes, Kerala Syllabus 8th Standard Basic Science Solutions Chapter 5 help you to revise complete Syllabus and score more marks in your examinations.

Kerala State Syllabus 8th Standard Basic Science Solutions Chapter 5 Basic Constituents of Matter

Basic Constituents of Matter Questions and Answers

The particles in sugar candy and potassium permanganate solutions cannot be seen as they are extremely small. If we take one or two pieces of camphor in a china dish and heat the china dish. Even though the camphor has disappeared completely, the smell of camphor remains in air. This is because the camphor has spread in air as extremely small particles.

Fill one quarter of a boiling tube with sugar and close it with cotton. Then heat the boiling tube strongly. The water in sugar is sticked on the sides of the boiling tube as water vapour. Carbon and water are the components of sugar. Water can be further divided. When electricity is passed through water it splits into hydrogen and oxygen. That is sugar, a pure substance, can be divided into carbon, hydrogen, and oxygen. At the same time, pure substances like carbon, hydrogen, oxygen, gold, and silver cannot be further divided into its components by chemical reactions.

Basic Constituents Of Matter Class 8 Kerala Syllabus Elements and Compounds

The pure substances which cannot be further decomposed through chemical processes are called elements.
Ex: hydrogen, oxygen, gold, silver Compounds are pure substances formed from two or more elements through chemical combination.
Ex : water, sugar, carbon dioxide

Origin of the names of elements

In the past, the elements were named after places, countries, continents, characteristic properties, scientists, planets, satellite etc.
Ex : Place – polonium, francium
Continent – Europium, Americium
Character, colour – rubedium, chromium
Scientist – bohrium, curium
Planet – neptunium

Basic Constituents Of Matter Class 8 Questions And Answers Kerala Syllabus Symbols

The first letter of the English or latin letters are used as the symbols of the ele-ments.
Ex: Carbon – C
Oxygen – O
Sodium-Natrium – Na
Potassium-Kalium – K
But, for some elements, along with the first letter, the second or another prominent letter is also used in the symbol as a small letter.
Ex: Calcium – Ca
Chlorine – Cl

Basic Constituents Of Matter Class 8 Notes Pdf Kerala Syllabus Atom and Molecule

The element carbon is made up of extremely small particles. Think of breaking a piece of carbon into smaller and smaller particles. When it is broken up in this manner, we get the smallest particle which retains all the characteristic properties of carbon at the end. This smallest particle is called an atom of carbon.

Atoms of some gaseous elements like helium, neon etc., can exist as free single atoms. But atoms of some other gaseous elements like hydrogen, oxygen etc., can exist only as a combination of two atoms. Atoms of some elements are seen to exist as a combination of more than two atoms. The smallest particles which can exist independently are called molecules.

Method of representing Atoms and Molecules

The symbol of helium is ‘He’. When we write ‘He’, it represents one atom of the element helium. 2He means two helium atoms.

Elements like helium, neon, argon, etc., are seen in nature as single atoms. But elements like hydrogen exist as diatomic molecules. Hydrogen atom is represented as H. But H₂ represents a hydrogen molecule.

Some elements exist as molecules of more than two atoms. Phosphorus (P₄), sulphur (S₈), etc., are examples of such
elements.

Molecules with only one atom are called monatomic molecules.
Ex: He, Na

Those with two atoms each are called diatomic molecules.
Eg: O₂, H₂, N₂

The molecules with more than two atoms are called polyatomic molecules.
Eg: P₄ S₈

In monatomic molecules, the number given on the left side of the symbol indicates the number of molecules and atoms. In polyatomic molecules, the subscript on the right side of the symbol indicates the number of atoms within one molecule. The total number of molecules is indicated on the left side.
O – One oxygen atom
O₂– One oxygen molecule
2O₂ – Two oxygen molecules
2He – Two helium atom/molecule
5Na – five sodium atoms

Basic Constituents Of Matter Kerala Syllabus  Compounds

We have seen how molecules are formed from the same type of atoms. Similarly, the compounds contain molecules formed from atoms of different elements.

Carbon dioxide molecule is formed when one carbon atom combines with one oxygen atom.

This is a compound. Water is a compound formed by the combination of hydrogen and oxygen.

Carbon dioxide is formed when carbon burns in oxygen. Carbon dioxide is also formed by the decomposition of calcium carbonate. Whatever be the sourcj of a compound, a fixed ratio is maintained between the atoms of the different elements present in it. In carbon dioxide molecule, the ratio of carbon atoms to oxygen atoms is always 1: 2. Thus carbon dioxide molecule can be represented as CO₂. Similarly in water molecule the ratio of hydrogen and oxygen atom is 2:1 This type of representation is known as the chemical formula of the compound.
H₂SO₄ ,CO₂ ,H₂O, HCl, NaCl

2CO₂ represents two carbondioxide molecules. We can understand that there are 6 atoms including 2 carbon atoms and 4 oxygen atoms in 2CO₂.

There are 7 atoms including 2 hydrogen atoms, 1 sulphur atom and 4 oxygen atoms in H₂ SO₄, Molecule. There will be 14 atoms in 2H₂ SO₄

Basic Constituents Of Matter Notes Kerala Syllabus Chemical Equations

The chemical equation of the reaction between zinc and hydrochloric acid forming zinc chloride and hydrogen is written as shown below.
Zn+HCl → ZnCl₂ + H₂

Here Zn and HCl are reactants. ZnCl₂ and H₂ are products.

The chemical reactions can be represented as equations containing the symbols and chemical formulae of the reacta¬nts and the products. When a chemical equation is written, the number of atoms of the same kind, on the side of reactants and that of products should be equal. That is the chemical equation given above is to be rewrite as
Zn + 2 HCl → ZnCl₂ + H₂

Now the number of atoms in both side of the arrow is equal. This type of chemical equations which is written such that the number of atoms of same type is equal in the side of reactants and products are called balanced chemical equations.

Basic Constituents of Matter Textbook Questions and Answers

Basic Science Class 8 Chapter 5 Kerala Syllabus Question 1.
Classify the following into elements and compounds. Ammonia, sugar, nitrogen, mercury, sodium chloride, water, copper sulphate, sodium, carbon.
Answe:

Hsslive Guru 8th Class Chemistry Kerala Syllabus Question 2.
Analyse the chemical equation given for the reaction between nitrogen and hydrogen to give ammonia.
N₂+3H₂ → 2NH₃
a. What are the reactants and products in this reaction?
b. Find the total number of molecules and atoms of the reactants.
c. Find the total number of molecules and atoms of the products.
d. What is the relation between the number of atoms of the reactants and products?
Answer:
a. Reactants: nitrogen, hydrogen Product: ammonia (NH₃)
b. Total number of molecules in reactant – 4 total atoms- 8
c. Total number of molecules in product -2 total atoms- 8
d. Total number of atoms in reactants and products are equal.

Hsslive Guru Chemistry 8 Kerala Syllabus Question 3.
N is the symbol of nitrogen.
a. What do N₂, 2N and 2N₂ indicate?
b. How many molecules and atoms are present in 5N₂?
Answer:
a. N₂ – One nitrogen molecule
2N – Two nitrogen atoms
2N₂ – Two nitrogen molecules
b. 5N₂ – 10 atoms, 5 molecules

Hss Live Guru 8th Chemistry Kerala Syllabus Question 4.
Some chemical equations are given.
C + O₂ → CO₂
CH₄ + 2O₂ → CO₂ + 2H₂O
N₂ + O₂ → NO
CaCO₃ → CaO + CO₂
H₂ + I₂ → HI
Fe + HCl → FeCl₂ + H₂
CO₂ + C → CO
a. Which of these are balanced chemical equations?
b. Balance those equations which are not balanced.
Answer:
a. C + O₂ → CO₂
CH₄ + 2O₂ → CO₂ + 2H₂O
CaCO₃ → CaO + CO₂

b. N₂ + O₂ → 2NO
H₂ + I₂ → 2Hl
Fe + HCl → FeCl₂ + H₂
CO₂ + C → 2CO

Basic Science Class 8 Solutions Kerala Syllabus Question 5.
Find whether the following statements are right or wrong.
a. All atoms of the same element show the same properties.
b. The atoms present in a compound are different.
c. Elements are pure substances.
d. Hydrogen is a monatomic molecule
Answer:
a. True
b. True
c. True
d. False

Matter And Chemical Formula Class 7 Kerala Syllabus Question 6.
Take iron powder and sulphur powder in their mass ratio of 7:4 in a china dish. Heat it strongly for some time.
a. Try to separate the iron powder using a magnet. What can be observed? What is the reason?
b. Add a .little dilute hydrochloric acid to the above product; observe the changes taking place, and write them down.
c. Write down the inferences you have arrived at from these observations.
Answer:
Sulphur is reacted with iron powder to form ferrous sulphide therefore it cannot be separated.
There will be the smell of rotten egg because hydrogen sulphide is produced.

8th Class Chemistry State Syllabus Kerala Syllabus Question 7.
Make and exhibit the models of the following molecules using ball and sticks, different fruits and splints.
a. Water (H₂O)
b. Ammonia (NH₃)
c. Carbon dioxide (CO₂)
d. Methane (CH₄)
Answer:
Do your self

Basic Science Class 8 Pdf Notes Kerala Syllabus Question 8.
Haven’t you understood how symbols are assigned to elements? Given below are some elements that received symbols from their Latin names. Complete the table with the help of the Periodic Table.

Answer:

Basic Constituents of Matter Additional Questions and Answers

Basic Science Question Answer Chapter Wise Class 8 Kerala Syllabus Question 1.
Choose the correct symbol of the elements given below from the box.
(Calcium, carbon, sodium, potassium, Iron, silver)
(S, C, Na, Ca, Si, Ag, In, P, K, Fe)
Answer:
Calcium-Ca,
Carbon-C,
Sodium- Na,
Potassium- K,
Iron- Fe,
Silver- Ag

Basic Science For Class 8 Chapter 5 Kerala Syllabus Question 2.
The chemical formula of calcium bisulphate is Ca (HSO₄)₂. Write down the number of atoms of each element present in this molecule.
Answer:
Ca=1, H=2, S=2, 0=8

Basic Science Class 8 Kerala Syllabus Question 3.
Na. This is the symbol of an element. Which statement given below is wrong. Justify?

• Symbol of Nitrogen
• Indicates one atom.

Answer:
Symbol of Nitrogen.
The symbol that represent the element Nitrogen is ‘N’. ‘Na’ is the symbol of sodium.

8th Class Chemistry Notes Pdf Kerala Syllabus Question 4.
We know about elements and compounds. Find out the odd one from the following. Give reason?
a. (A) Hydrogen (B) Oxygen (C)Nitrogen (D) Carbon dioxide
b. (A) Sodium (Na), (B) Pottasium (K) (C) Magnesium (Mg), (D) Iron (Fe)
c. Write the molecular formula of carbon dioxide?
d. What is the Latin name of sodium?
Answer:
a. Carbon dioxide – Compound, others are elements.
b. Magnesium – Others take symbols from their Latin name.
c. CO₂
d. Natrium

8th Std Basic Science Textbook Kerala Syllabus Question 5.
Arrange the following from smallest to largest.

Answer:
Atom → Molecule → Small particle → Substances

Physics Class 8 Kerala Syllabus Question 6.
Represent the basis of nomenclature of elements given in the following table.
a.

b. Which element symbol is Cl?
c. What are the constitute elements containing of CaF₂ molecule?
Answer:
a. Name of country
b. Name of scientist
c. Chlorine
d. Calcium, -Fluorine

Question 7.
Symbol of Nitrogen is ‘N’.
a. What represent symbols of 2N and N₂?
b. How many atoms are in 2NH₃?
c. How can represent 5 water molecules?
Answer:
a. 2N represent 2 atoms of Nftrogen. N₂ represent Nitrogen molecules can be formed by combining two atoms of Nitrogen.
b. 8 atoms
c. 5 H₂O

Question 8.
Evaluate the given chemical equation and answer the following questions.
SO₂ + O₂ – SO₃
a. Which are the reactants in the chemical reaction?
b. What is the product of the chemical reaction?
c. Write the balanced chemical equation?
Answer:
a. SO₂, O₂
b. SO₃
c. 2SO₂ + O₂ → 2SO₃

Question 9.
Find the monoatomic molecule from given elements.
a. (A) Hydrogen (B) Oxygen (C)Nitrogen (D) Helium
b. Write the symbols of Hydrogen and Helium?
c. Write chemical formula of Oxygen molecule?
d. What is the Latin name of sodium?
Answer:
a. (D) Helium
b. Hydrogen (H), Helium (He)
c. O
d. Natrium

Question 10.
Select the compounds from the following:
HCl, CO₂, O₂, NaCl, H₂, H₂O, Na, HCl
Answer:
NaCl, CO₂, H₂O, HCl

Question 11.
Form a table of elements which are related to the name of scientists from the following Americum, Mentelivium, Titanium, Rutherfordium, Rubedium, Einstenium, Europeum, Bohrium
Answer:
Mentelivium, Rutherfordium, Einstenium, Bohrium

Question 12.
Examine the following symbols and write the name of elements Ca, Cr, Cl, Be, Na, Fe, Cu
Answer:
Calcium, Chromium, Chlorine, Berelium, Sodium, Iron, Copper

Question 13.
Fill in Blanks suitably
Element – Atom,
Compound – …………
Answer:
Element – Atom,
Compound – Molecule

Question 14.
Complete the following table

Answer:

Question 15.
Examine the following molecules and tabulate the atoms contained in them.
1. Carbon dioxide
2. hydrogen chloride
3. Water
4. sugar
5. Mercuric oxide
Answer:
1. C, O;
2. H, Cl
3- H, O;
4. H, C, O;
5- Hg, 0

Question 16.
Complete the tables

Answer:

Question 17.
Tabulate the number of atoms and molecules
5H₂, 2H₂ O, 3ZnCl₂, CO₂
Answer:

Question 18.
Write the diatomic molecules from the following
H₂, Na, C, N₂, P₄, O₂
Answer:
H₂, N₂, O₂

Question 19.
Complete the table

Answer:

Question 20.
How many hydrogen and sulphur atoms are there in H₂SO₄ molecule?
Answer:
Hydrogen-2 Sulphar-1

Question 21.
Complete the table.

Answer:

Question 22.
Find the total number of atoms in the following molecules
a. CO
b. 5 H₂O
c. 7 NH₃
d. 2 Cl₂ H₂₂ O₁₁
e. 3 NaCl
f. ZnCl₂
Answer:
a. CO – 2
b. 5 H₂O -15;
c. 7 NH₃ – 28;
d. 2C₂ H₂₂ O₁₁ – 90
e. 3 NaCl – 6
f. ZnCl₂ – 3

Question 23.
The chemical formula of water is H₂O. Write the ratio of hydrogen and oxygen atoms in water molecule.
Answer:
Ratio of hydrogen and oxygen is 2:1

Question 24.
Tabulate the reactants and products in the following chemical equation.
1. 2H₂ + O₂ → 2H₂O
2. Na + Cl₂ → 2NaCl
3. C + O₂ → CO₂
4. H₂ +Cl₂ → 2HCl
Answer:

Question 25.
Balance the following equations which are not balanced.
C + O₂ → CO₂
H₂ + N₂ → NH₃
Mg + O₂ → Mgo
2H₂ + O₂ → 2H₂O
Answer:
3 H₂ + N₂ → 2NH₃
2Mg+O₂ → 2MgO

Question 26.
How did the symbol system introduced by Berzelius, help the study of chemistry?
Answer:

• The study of chemistry became simple and easy.
• Writing chemical equations representing chemical reactions became very easy.
• The number of atoms in a molecule can be found out from the symbol of the molecule of the element.

Question 27.
Balance the equation
1. NaOH + H₂ SO₄ → Na₂ SO₄ + H₂O
2. H₂O₂ → H₂O + O₂
3. CH₄ + O₂ → CO₂ + H₂O
4. NaOH + HCl → NaCl + H₂O
5. H₂O + CO₂ → C₆H₁₂O₆ + O₂
Answer:
2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O
2H₂ O₂ → 2HO₂ + O₂
CH₄ +O₂ → CO₂ + 2H₂O
2NaOH + 2HCl → 2NaCl + 2H₂O
6 H₂O + 6CO₂ → C₆ H₁₂ + 6 O₂

You can Download Sound Questions and Answers, Summary, Activity, Notes, Kerala Syllabus 8th Standard Basic Science Solutions Chapter 19 help you to revise complete Syllabus and score more marks in your examinations.

Kerala State Syllabus 8th Standard Basic Science Solutions Chapter 19 Sound

Sound is a form of energy which is familiar to us and necessary for communication. Three components are essential to experience the sound. Source of sound, medium, and the ear.

Source of sound

The sources that produce sound is called sources of sound. We can classify the sources of sound into two. Natural sources of sound and manmade sources of sound. Sound is produced by the vibration of object. The object that produces sound is called the source of sound.

Hss Live Guru 8th Physics Kerala Syllabus Natural frequency

When a body is set into vibration it vibrates with particular frequency of its own. This frequency is called its natural frequency. The unit of frequency is hertz (Hz). The constituents those affect the natural frequency of an object are the nature of the object, length of the object, surface area, tension of the object, etc.
Frequency (f) = Number of vibration(n)/ time(f)

Pitch and loudness

The sharpness of the sound heard is called the pitch. It depends on its frequency of sound. Cuckoo’s cry, female voice etc have high pitch and male voice, duck’s sound, lion’s roar, etc have low pitch. Loudness is the measure of audibility of a person. This depends mainly on frequency of sound and the sensory ability of the ear. Its unit is decibel (dB).

Kerala Syllabus 8th Standard Physics Notes Propagation of sound

A medium is necessary for sound to propagate. Sound is propagated not only through air but also through other substances. Loss of hearing is a disability of the ear. The people having damage to ear by birth effect many difficulties for commu¬nication, for ability to speak, vulnerability to danger, etc.

Class 8 Physics Notes Kerala Syllabus Limit of audibility

We cannot here sound of all frequencies. We can hear the sound of frequency in between 20 Hz and 20000Hz. Sounds with frequency less than 20 Hz are called infrasonic and that greater than 20000Hz are called ultrasonic. Ultrasonic sounds are used in the instrument sonar and in medical field.

Hss Live Guru 8th Basic Science Kerala Syllabus Noise pollution

Kerala is one of the places which is highest noise pollution in the world. Noise effects not only ear but mental, emotional level, and physical problems. Reduce the use of air horns, use silencers in vehicles, planting trees, etc are some ways to reduce noise pollution.

Sound Textbook Questions & Answers

Hsslive Guru Physics 8th Standard Kerala Syllabus Question 1.
If a tuning fork vibrates 480 times in one second, what would be its natural frequency?
Answer:
Natural frequency = 480Hz

Kerala Syllabus 8th Standard Chemistry Notes Question 2.
If a simple pendulum oscillates 10 times in 10 seconds, what would be its frequency?
Answer:
n = 10
t = -10 s
\(\mathrm{f}=\frac{n}{t}=\frac{10}{10 s}=1 \mathrm{Hz}\)

Hsslive Guru 8th Class Physics Kerala Syllabus Question 3.
What are the factors influencing the natural frequency of a body?
Answer:
i. Nature of the object
ii. Length
iii. Tention
iv. Surface area
v. Area of cross-section

Hss Live Physics Class 8 Kerala Syllabus Question 4.
The frequencies of certain tuning forks are given below. Find out which among these have the highest and the smallest pitches.
(256 Hz, 512 Hz, 480 Hz, 288 Hz)
Answer:
High pitch = 512 Hz
Low pitch = 256 Hz

Kerala Syllabus 8th Standard Basic Science Notes Question 5.
In the sources of sound given below, vibration in which main part produces sound?
a. Chenda
b. Flute
c. Vocal cord
Answer:
a. Chenda – Diaphragm
b. Flute-Air
c. Vocal box – vocal cord

Kerala Syllabus 8th Standard Chemistry Notes Malayalam Medium Question 6.
Design an activity to prove that sound can he propagated even through solid substances.
Answer:
Answer:
Press the ear on one end of a iron rod and beat on the other end with another iron rod or, toy telephone

8th Standard Physics Notes Kerala Syllabus Question 7.
Say whether the following statements given below are true or false.
If false, rewrite it by making necessary changes.
a. Sound cannot travel through vacuum.
b. When frequency of sound increases, pitch decreases.
Answer:
a. correct
b. false, when frequency decreases pitch decreases

Kerala Syllabus 8th Standard Physics Question 8.
‘Bats can catch prey even in the dark’. Do you agree with this statement? Explain your inference.
Answer:
Agree. Bats can produce and hear ultrasonic waves. The sound they produced reflects by hitting on objects. The bats can analyze the returning sounds.

8th Class Biology Notes Pdf Kerala Syllabus Question 9.
How do human beings contribute to noise pollution?
Answer:

• Air horn
• Loudspeaker
• The sounds of vehicles etc

8th Standard Chemistry Notes Pdf Kerala Syllabus Question 10.
Which unit represents loudness? (Hz, m/s, dB, W)
Answer:
dB

Sound Additional Questions & Answers

8th Standard Chemistry Notes Kerala Syllabus Question 1.
Complete the table

Answer:

Basic Science Class 8 Sound Kerala Syllabus Question 2.
Fill suitably
Frequency – hertz; Loudness- ………….
Answer:
decibel (dB)

Class 8 Science Notes Kerala Syllabus Question 3.
Table the following as those having high pitch and low pitch separately.
Cuckoo’s cry, lion’s roar, female voice, duck’s sound, male voice, air horn
Answer:

Class 8 Physics Kerala Syllabus Question 4.
Table the natural source and manmade source from the following. Lips, chenda, flute, tabla, violin, vocal cord, sound of birds
Answer:

Vibration Solutions Question 5.
What is the relation between the length of the pendulum and frequency?
Answer:
When the length of the pendulum increases, the frequency decreases.

Question 6.
Will the intensity of sound increase when the instrument like chenda and maddalam are beaten strongly? Justify your answer.
Answer:
Yes. When beaten strongly the diagram vibrates with greater amplitude and increases frequency and loudness

Question 7.
What are the demerits of sound pollution?
Answer:

• Causes mental stress.
• Causes emotional strain
• Causes deafness
• Increase the blood pressure

Question 8.
Write the ways to reduce sound pollution.
Answer:

• Ban the air horn
• Control loudspeakers
• Use silencers in vehicles
• Control the sound having more than 50 dB near the hospitals

Question 9.
Write two uses of ultrasonic sound.
Answer:
Use in SONAR
To find out the disease and treatment in medical field

Question 10.
Can we hear the sound from Galton whistle having a frequency of 30000Hz? Why?
Answer:
No. We cannot hear the sound having a frequency greater than 20000Hz

Question 11.
What are the problem faced by deaf people?
Answer:
The people having damage to hereby birth effect many difficulties for com¬munication, for ability to speak, vulnerability to danger, etc.

Question 12.
Complete the table.

Answer:
a. 5
b. 5
c. 20

Question 13.
An object vibrates 200 times in one second. What is its frequency?
Answer:
frequency = \(\frac{n}{t}=\frac{200}{1}=200 \mathrm{Hz}\)

Question 14.
How many times vibrate a body of frequency 290 Hz in 12 seconds.
Answer:
n = f × t
f = 290 Hz,
t = 12 s
n = 290 × 12 = 3480 times

Question 15.
Name the sounds of frequency below 20 Hz and above 20000 Hz.
Answer:
below 20 Hz = Infrasonic
Above 20000 Hz = ultrasonic

You can Download सफेद गुड़ Questions and Answers, Summary, Activity, Notes, Kerala Syllabus 8th Standard Hindi Solutions Unit 5 Chapter 1 help you to revise complete Syllabus and score more marks in your examinations.

Kerala State Syllabus 8th Standard Hindi Solutions Unit 5 Chapter 1 सफेद गुड़

सफेद गुड़ पाठ्यपुस्तक के प्रश्न और उत्तर

Safed Gud Story In Hindi Kerala Syllabus 8th प्रश्ना 1.
माँ के आसमान की ओर देखने का क्या कारण होगा?

उत्तर:
माँ चाहती होगी कि बेटे को पैसा दें। लेकिन वह विवश है। वह अपनी विवशता के कारण आकाश की ओर ताकती है। पैसे के अभाव में वह हमेशा ऐसा करती है। शायद वह ईश्वर से विनती करती होगी।

Safed Gud Kahani Ka Saransh Likho Kerala Syllabus 8th प्रश्ना 2.
वह अपने को धिक्कारने लगा और इस बुरे ख्याल के लिए ईश्वर से क्षमा माँगने लगा’ -यहाँ लड़के का कौन-सा मनोभाव प्रकट है?

उत्तर:
इससे बच्चे का विवेकशीलता प्रकट होता है। उसकी सच्चाई और गलती पर पछताने का भाव यहाँ स्पष्ट है।

Gud In Hindi Kerala Syllabus 8th प्रश्ना 3.
वह एक अठन्नी ही नहीं थी, उस गरीब पर ईश्वर की कृपा थी -ऐसा क्यों कहा है?

उत्तर:
वह पैसे के लिए बहुत तरसता था। बहुत प्रार्थना भी किया था। इसी अवसर पर उसे यह अठन्नी मिली। इसलिए उसे लगा कि वह ईश्वर की कृपा है।

सफेद गुड़ Textbook Activities

सफेद गुड कहानी का सारांश Kerala Syllabus 8th प्रश्ना 1.
निम्न्लिखित वाक्य पर घ्यान दें —

माँ बैठी फटे कपड़े सिल रही थी।

बताएँ, रेखांकित शब्दों में क्या संबंध है?

उत्तर:

Gud Meaning In Hindi Kerala Syllabus 8th प्रश्ना 4.
इस प्रकार आपसी संबंध रखनेवाले शब्द पाठ से चुनकर लिखें।

उत्तर:

Prarthana Poem In Hindi 8th Class Summary Kerala Syllabus 8th प्रश्ना 5.
लड़के की गुड़ खाने की इच्छा सफल नहीं हुई। उसके विचारों को डायरी के रूप में लिखें।

उत्तर:
25 जनवरी 2016
बहुत दिनों से गुड़ खाने की इच्छा थी। आज सोचा कि वह सफल हो गया। लेकिन क्या कहूँ, वह सपना सपना ही रह गया। नमक खरीदने बाज़ार जाते समय एक पैसे के लिए प्रार्थना करता रहा। ठीक उसी समय ज़मीन से एक अठन्नी पड़ी मिली। खुशी का ठिकाना न था। अफ़सोस है कि दुकानदार को देते समय वह हाथ से खिसक गया, धनिया के डिब्बे में। ढूँढ़ने से चिकना-सा पत्थर मिला। दुकानदार ने कहा कि मुफ्त में ले लो। लेकिन मन नहीं हुआ। नमक खरीद कर दुखी मन से वापस चला आया।

सफेद गुड़ Summary in Malayalam and Translation

सफेद गुड़ शब्दार्थ Word meanings

You can Download Fibres and Plastics Questions and Answers, Summary, Activity, Notes, Kerala Syllabus 8th Standard Basic Science Solutions Chapter 17 help you to revise complete Syllabus and score more marks in your examinations.

Kerala State Syllabus 8th Standard Basic Science Solutions Chapter 17 Fibres and Plastics

We have variety of substances around us for improving our lifestyle. The natural resources are utilised to produce a variety of modern materials.

Fibres And Plastics Class 8 Kerala Syllabus Polymers

Cotton. Silk, jute, wool, rubber etc are the molecules belonging the group of polymers. Polymers are macromolecules formed by the combination of large number of simple molecules called monomers. Fibres are the polymers suitable for the manufacture of strong threads. Plastics are the polymers which can be moulded into different shapes. Rubber is an elastic polymer.

Manmade polymers

In order to overcome the demerits like less availability, less durability etc several synthetic polymers have been prepared through chemical methods. Synthetic threads have demerits too. Some of them are low aeration, low ability to absorb water, high inflammability etc

Basic Science Class 8 Chapter 17 Kerala Syllabus Plastic

These are the substances that changed the very face of human life which are having different properties.

Thermoplastics and thermosetting plastics

The plastic that gets softened on heating and hardened on cooling is thermoplastics. The plastic which remains soft when heated during its manufacture, and gets hardened permanently on cooling is thermosetting plastics.

Plastics and Pollution

Even though plastics are very useful substance, the careless use and misuse lead to environmental pollution. Plastics give many benefits to mankind. Forest conservation, household utility etc are some of the benefits. There are many ways to reduce pollution due to plastics. Some of them reduce the use of dispo¬sable plastics, reduce; the overuse of plastic materials, use other material like glass, ceramic materials instead of plastic etc.

Fibres and Plastics Textbook Questions and Answers

Basic Science For Class 8 Chapter 17 Kerala Syllabus Questions 1.
Polymers are macromolecules formed by the combination of many monomers.
a. How are polymers classified?
b. Classify the following:
Cotton, Wool, Nylon, Silk, Terylene, Jute, Polyester
Answer:
a. i. On the basis of its formation as natural and man-made.
ii. On the basis of structure as linear branches chain, cross-linked chain
iii. On the basis of process as addition polymer and condensation polymer.
iv. On the basis of molecular strength as fibres and plastics
b. Natural: wool, silk, jute, cotton Man-made: Nylon, Terylene, Polyester

Kerala Syllabus 8th Standard Physics Notes Questions 2.
Some monomers and polymers are given in the following table:

a. What is meant by the terms ‘monomer’ and ‘polymer’?
b. What is the common system of nomenclature of polymers?
Analyse the table and find out.
Answer:
a. Monomer: A Simple molecule having a particular structure
Polymer: Macromolecules formed by combination of large number of monomers.
b. Add the word ‘poly’ before the name of monomer.

Kerala Syllabus 8th Standard Chemistry Notes Question 3.
Natural fibres and synthetic fibres are used in the field of textile manufacturing.
a. Compare their merits and demerits and tabulate.
b. Which of these clothes is most suited for the following situations? Give reason.
i. While cooking in the kitchen
ii. To wear during summer
Answer:
a. Merits:

• Comfortable to wear
• Not inflammable
• Ability to absorb water
• High aeration

Demerits:

• Less available
• Less durability
• Wrinkle easily
• Cannot dry easily on getting wet

b. Natural fibres:- Because they are not inflammable, have ability to absorb sweat, high aeration

8th Class Biology Notes Pdf Kerala Syllabus Question 4.
You know what thermoplastics and thermosetting plastics are.
a. Which of these plastics cannot be recycled?
b.You might have noticed that those who collect old plastics do not accept certain type of plastic articles. What are they? What may be the reason for this?
Answer:
a. Thermoplastic
b. Thermosetting plastic. Because they can’t be recycled.

Kerala Syllabus 8th Standard Biology Notes Question 5.
Some argue that plastics are to be completely banned as they cause environmental pollution. What is your view?
Answer:
No. Without plastic, we cannot manage daily life. Control the use of plastic. avoid disposable plastic products and use thermoplastic materials.

8th Class Biology Notes Pdf Malayalam Medium Question 6.
The school science club has N decided to conduct a poster propaganda for creating awareness about pollution due to plastics. Prepare some posters for this.
Answer:
Avoid disposable plastic products use glass, ceramic utensils or natural substances
Use paper or natural materials fo decorations
Don’t dump plastic materials in soil.

8th Standard Basic Science Textbook Kerala Syllabus Question 7.
What suggestions can you propose to realise the concept of ‘plastic waste-free school’? List your findings.
Answer:
Reduce: Buy only what you need because a better way to reduce waste is by not creating it.
Reuse: Instead of throwing out plastic product you no longer think you need, try repurposing them because plastics exist for long time. Eg: use refill in ball pens, use thick plastics which can be reused, reuse the plastic bottle. The banning of plastics below the thickness of 30 micron aims at this. When thickness increases a tendency will arise to use it again.

Recycling: Is the process by which the plastics which is rendered useless is heated and subjected to certain processes to produces new materials. Recycling the rate of environmental pollution

Refuse: We can avoid the use of plastic when it is not necessary. Avoid thin plastic covers when things are bought. Use cloth bag, paper bag or thick plastic covers which can be used for long time

Fibres and Plastics Additional Questions and Answers

8th Biology Notes Malayalam Medium Kerala Syllabus Question 1.
Differentiate between thermoplastic and thermosetting plastic.
Answer:
The plastic that gets softened on heating and hardened on cooling is thermoplastic. When heating physical change occurs.
The plastic which remains soft when heated and gets hardened permanently on cooling is thermosetting plastics. Chemical change occurs when heating.

Kerala Syllabus 8th Standard Biology Notes Malayalam Medium Question 2.
Given some occasions of using plastic. Find the peculiarity of plastic used and fill the table.
Answer:

Answer:

Kerala Syllabus 8th Standard Chemistry Notes Malayalam Medium Question 3.
Write 4 occasions which plastic is harmful to daily life.
Answer:

1. Environmental pollution when it is thrown without any control.
2. When burning it cause air pollution.
3. Hindrance in drainages
4. The water absorption property of soil decreases when plastics are dumped in soil.

Kerala Syllabus 8th Standard Notes Question 4.
What are the uses of plastic in the field of human health?
Answer:
To produce IV tubes, bottles To produce heart valves To produce packets

Synthetic Fibres And Plastics Class 8 Notes Kerala Syllabus Question 5.
What are the uses of plastic in the field of production of house building?
Answer:
To produce roof materials, doors, plumbing and wiring materials.

Class 8 Chemistry Notes Kerala Syllabus  Question 6.
List the peculiarities of plastic.
Answer:
Can mould in any shape, longlasting, insulator, do not conduct heats, not reacting with chemicals and water, will burn.

Question 7.
Separate natural and artificial polymer from the list
Rubber, wool, Pvc, Bakelite, nylon, rayon cellulose, silk, polythene, polyester
Answer:

Question 8.
List the merits of natural and artificial polymer
Answer:

Question 9.
If we heat polyethene cover can we convert into earlier stage? Justify.
Answer:
No. Undergoes chemical change because it is thermosetting plastic.

Question 10.
Filling in the blanks.
1. Natural polymer is ……………
2. Insulin is a ………….
3. is a monomer of polythene. …………..
4. Nylon is type of plastic. …………….
5. Bakelite is an example for plastic. …………..
6. Natural polymer which has elastic nature is ……………
7. Inflammable tendency is higher in …………….
8. Thermoplastic is a ……………. type polymer.
9. The constituent unit of polymer is called
10. Polymers of plant origin are made up of …………..
Answer:
1. Starch
2. Protein
3. Ethylene
4. thermoplastic
5. thermosetting
6. Rubber
7. Synthetic fibres.
8. linear
9. monomer
10. cellulose

Question 11.
Give examples for natural fibres.
Answer:
Coconut husk, cotton, hemp, silk etc.

Question 12.
What is vulcanization? What is the use of it?
Answer:
’The process of heating rubber with sulphur is called vulcanization. By vulcanization rubber retains its form and to increase the hardness, Moreover, tensile strength, elasticity keeping stability at high temperature etc. are increased.

Question 13.
Give four difference between natural rubber and synthetic rubber.
Answer:
1. Synthetic rubber is harder than natural rubber.
2. Natural rubber is easily flammable.
3. The elasticity of natural rubber is lower than that of synthetic rubber.
4. Synthetic rubber keeps stability at higher temperature.

Question 14.
Classify the following into thermoplastic and thermosetting plastics.
Bakelite, polyvinyl chloride, nylon, celluloid, urea-formaldehyde, Teflon, polyester, polythene.
Answer:

Question 15.
Find out odd one and give reason. Bakelite, polyester, polythene, melamine formaldehyde.
Answer:
Polythene: All the others are thermosetting plastics.

You can Download For the Continuity of Generations Questions and Answers, Summary, Activity, Notes, Kerala Syllabus 8th Standard Basic Science Solutions Chapter 14 help you to revise complete Syllabus and score more marks in your examinations.

Kerala State Syllabus 8th Standard Basic Science Solutions Chapter 14 For the Continuity of Generations

For the Continuity of Generations Textbook Questions and Answers

For The Continuity Of Generations Biology Kerala Syllabus 8th Reproduction

In nature, there are various methods of reproduction to produce new generations.

For The Continuity Of Generations Kerala Syllabus 8th Budding

This is a method of asexual reproduction seen in Hydra, Yeast etc. The buds formed from the parent body detaches from it when mature and develop into a new organism.

Basic Science Class 8 Chapter 14 Kerala Syllabus Binary fission

Binary fission is seen in prokaryotes. Existing cell divides to form 2 new cells. In favorable conditions, bacteria-like organisms reproduce by binary fission

Kerala Syllabus 8th Standard Chemistry Notes Spore formation

This type of asexual reproduction is seen mainly in fungus. Spores are microscopic cells that can survive unfavourable conditions and develop into new organism on the return of favourable season.

Basic Science For Class 8 Chapter 14 Kerala Syllabus Pollination, Fertilization

Flowers are the sex organs in plants. Pollination is the process of transfer of pollen grains to the stigma of the flower. After pollination pollen tube grows towards the ovary. Simultaneously generative nucleus in the pollen grain divides at the pollen tube and two sperms are formed.
One of the sperms fuses with the ovum and forms the zygote. This process is called fertilization. The second sperm fuses with the polar nucleus in the ovary and forms the endosperm. Zygote develops into embryo and endosperm becomes the stored food for the growth of embryo.

Indicators (Text Book Page No:200)

Kerala Syllabus 8th Standard Chemistry Notes Malayalam Medium Questions 1.
Formation of male gametes
Answer:
After the pollination pollen tube grows towards the ovary. Simultaneously generative nucleus in the pollen grain divides at the pollen tube and two sperms are formed.

8th Class Biology Notes Pdf Malayalam Medium Questions 2.
Formation of embryo
Answer:
One of the sperms fuses with the ovum and forms the zygote. This process is called fertilization.

8th Class Biology Notes Pdf Kerala Syllabus Questions 3.
Formation of endosperm and its function
Answer:
The second sperm fuses with the polar nucleus in the ovary and forms the endosperm. Zygote develops into embryo and endosperm becomes the stored food for the growth of embryo.

8th Standard Chemistry Textbook Kerala Syllabus Male Reproductive system

The main parts of male reproductive system are Vas deferens, prostate gland, penis, testis etc.

Basic Science Class 8 Chapter 14 Solution Kerala Syllabus Vas deferens

Carries sperms from testis to urinary tract.

8th Standard Chemistry Textbook Kerala Syllabus Prostate gland

Secretes a fluid that contains factors required for the movement and nourishment of sperms.

Biology Class 8 Malayalam Medium Kerala Syllabus Penis

Deposits sperms into vagina

Basic Science Question Answer Chapter Wise Class 8 Testis

Produces sperms and male hormones.

Class 8 Science Notes Pdf State Syllabus  Sperm

Sperm is motile. It has a head, middle piece and tail. Mitochondria present in the middle piece provides energy for movement. In the head, nucleus containing paternal chromosomes are present.

Indicators (Text Book Page No:201)

Questions 4.
Characteristics of sperms
Answer:
Sperms:- Sperms are motile. It has a head, middle piece and tail. Mitochondria present in the middle piece provide energy for movement. In the head, nucleus containing paternal chromosomes is present.

Questions 5.
Location of testes and the production of sperms
Answer:
Testis are found in the scrotal sac outside abdominal cavity. Sperms are produced in the testis.

Questions 6.
Importance of glands
Answer:
Sperms reach the penis along with the fluid produced by accessory glands and they are secreted to outside. Secretions provide a medium for the movement of sperms and nourishment

Female Reproductive System

Ovaries, Oviduct, Uterus, Endometrium, Vagina, etc., are the parts of female reproductive system.
Ovary – Produces Ovum and female hormones.
Oviduct – Fertilization takes place in oviduct.
Uterus – Foetus completes its development in uterus.
Endometrium – Inner layer of Uterus. Foetus attach the endometrial wall.
Vagina – Uterus opens out through Vagina. Sperms are deposited here.

Ovum

Ovum is larger than sperms. They are non-motile. There are specified membranes outside the cell membrane of ovum.

Indicators (Text Book Page No:202)

Questions 7.
Characteristics of ovum
Answer:
Ovum is larger than sperms. They are non-motile. There are specified membranes outside the cell membrane of ovum.

Questions 8.
Function of ovary
Answer:
Produces ovum and female hormones.

Questions 9.
Completing the table (Text Book Page No:202)

Answer:

Menstruation

With the onset of ovulation, there are certain preparations in the uterus to facilitate embryonic development. Endometrium becomes thickened, and more capillary are formed. But if fertilization does not take place the newly formed tissues disintegrate and peel off from the uterine wall. These get eliminated to outside along with blood and mu¬cus through vagina. This process is called menstruation.

Fertilization

Fertilization is the process of fusion of ovum, that releases from the ovary with the sperm in the oviduct.

Placenta

It is the part that connects embryo with the endometrium. Oxygen and nutrients are supplied to the foetus through the umbilical cord formed from the placenta. Waste materials from the foetus are also eliminated through placenta.

Questions 10.
Completing the table (Text Book Page NO:204)

Answer:

Indicators (Text Book Page No:206)

Question 11.
What is adolescence?
Answer:
Adolescence is the period between puberty and adulthood.

Question 12.
How does adolescence influence the physical and mental development of an individual?
Answer:
The characteristics of adolescence like brain development, rapid increase in the height and weight, growth of reproduction organs, increased efficiency of glands, etc., influence the physical and natural development of individuals.

Question 13.
Why is the rate of adolescence growth higher in girls than in boys?
Answer:
In girls, the parts of brain that control physical and mental changes develop fast.

Question 14.
Is there any need to be anxious about the physical changes during adolescence? Why?
Answer:
No Adolescence is only a stage in growth. Bodily changes are part of development into a fully mature organism.

Adolescence and Food

Indicators (Text Book Page No:206)

Question 15.
What is the circumstance that led to the supply of iron-folic acid tablets to students?
Answer:
In adolescence severe anemia, due to deficiency of Iron was reported.

Question 16.
What is the role of food habits to overcome this situation?
Answer:
Including leafy vegetables, eggs, amaranthus, liver, etc., in the diet will help to check diseases like anemia.

Question 17.
How should the food habits be regularised so as to ensure the availability of nutrients for the rapid growth of body in adolescence?
Answer:
Vegetables, leafy vegetables, milk, egg, cereals, pulses, etc., should be included in the diet.

Need for assertiveness

Question 18.
What is your response towards this statement?
Answer:
Agree

Question 19.
Can you cite such instances?
Answer:
Invitation to practice alcohol, drugs, sex abuse, etc., temptation to do the dont’s, instances of crimes, etc.

Question 20.
How will you respond if such instances occur in your life?
Answer:
Say ‘No’.

Let us assess (Text Book Page No:211)

Question 21.
Which of the following activities takes place after fertilization in plants?
A. Pollen tube grows
B. Egg is formed in the ovary
C. Ovule becomes the seed
D. Male gametes are formed
Answer:
C. Ovule becomes the seed

Question 22.
Which part helps in the transportation of materials without mixing maternal and foetal blood?
A. Endometrium
B. Uterus
C. Placenta
D. Amni
Answer:
C. Placenta

Question 23.
Sequentially arrange the process that takes place after pollination in plants.
1. Embryo is formed
2. Pollen tube grows
3. Fertilization takes place
4. Male gametes are formed
5. Zygote is formed
6. Generative nucleus divides
Answer:
1. Pollen tube grows
2. Generative nucleus divides
3. Sperms are formed
4. Fertilization takes place
5. Zygote is formed
6. Foetus is developed

Question 24.
Substantiate the statement: “Excessive likes and dislikes of food materials adversely affects the health”.
Answer:
Avoiding food in order to become slim causes many diseases like anorexia. Overeating causes obesity and other chronic diseases.

Question 25.
Home hygiene and social hygiene are as important as personal hygiene for health. Do you agree with this opinion of the doctor who led an awareness class on health? Why?
Answer:
Definitely, unhygienic environment helps in the proliferation of pathogens. The dangers caused by pollution is much dreaded. Therefore home hygienic and social hygiene are very important as personal hygiene.

Question 26.
“Adolescence is full of challenges and possibilities”.
a. What are the challenges faced by adolescents?
b. What are your suggestions to overcome these challenges?
Answer:

• Causes mental and emotional disturbances.
• Confusion about his/her role in the society.
• Poor understanding about hygiene, immaturity.
• Possibility to addiction to bad habits.
• To survive these challenges
• Practice to say ‘No’ to wrong ways
• Parents should take care to make the environment in home pleasant
• Be careful while choosing friends.
• Take part in social services.
• Participate in co-curricular activities in the school.

Question 27.
It is easy to be addicted to drugs. But to escape from it is not that easy.
a. What should be our approach towards drugs?
b. What are the harmful effects of drugs?
Answer:
Never use drugs in your life. A single-use may push us to its addiction.

Harmful Effects

• Disease that leads to cancer are caused.
• Loss of social recognition
• Breaks interpersonal relationships. Loss of peace in the family and distortion of family relationship.
• Financial crisis arise
• Possibility to indulge in crimes

For the Continuity of Generations Additional Questions & Answers

Question 28.
Prepare a short note on the mode of reproduction in the organisms mentioned below. (Hydra, Bacteria, Fungi)
Answer:
Hydra: reproduces by budding. Buds are formed on the parent body. When it grows it gets detached from the parent and develops into new organisms.
Bacteria: reproduces by binary fission. An existing cell divides to two new cells.
Fungi: reproduces by spore formation.

Question 29.
Night-blooming flowers are while and having intense fragrance why?
Answer:
The smell and color of flowers is to attract insects.

Question 30.
“The disappearance of certain plants caused the extinction of some insects”- substantiate this statement.
Answer:
Certain insects depend only specific plants for their food and reproductive purposes; especially butterflies. Hence their destruction way leads to the extinction of the dependant species.

Question 31.
What is the function of tube nucleus and generative nucleus?
Answer:
Generative nucleus divides to form sperms. Tube nucleus disintegrates.

Question 32.
How does endosperm form?
Answer:
The second sperm fuses with the polar nucleus in the ovary and forms the endosperm.

Question 33.
What is the fate of Zygote, endo spermete?
Answer:
Zygote develops into embryo and endosperm forms the stored food for the development of embryo.

Question 34.
Find out the parts of the male reproductive system that performs the following functions?
1. Secrets the fluid containing nutrients for sperms
2. Secretes male hormones.
3. Carries sperms from the testis to ureter.
Answer:
1. Prostate gland
2. Testis
3. Vas deferens

Question 35.
Arrange the following state¬ments under the headings sperm Ovum.
1. Nonmotile
2. Parts like head, middle piece and tail are present.
3. Nucleus is present in the head,
4. Mitochondria is in middle piece.
Answer:

Question 36.
Are Ovulation and menstruation the same process?
Answer:
No. Ovulation is the process of release of mature ovum from the ovary. If fertilization does not take place the newly formed tissues in the uterine wall peel off and come, out along with blood and mucus through vagina. This process is called menstruation.

Question 37.
Find the odd one. Write the reason.
Endometrium, androgen, Oes-trogen, progesterone.
Answer:
Endometrium – Inner layer of uterus. Others are hormones.

Question 38.
How does placenta form? What is its function?
Answer:
Placenta is formed of fetal tissues and uterine tissues. Oxygen and nutrients are supplied to the fetus and waste materials are eliminated through the umbilical cord formed from placenta.

Question 39.
Fill in the blanks
1. Mushrooms are plants that reproduce by means of
2. During favorable conditions amoeba reproduces by
3. In tapeworm, both the male and female sex organs are found in the same organism. So it is said to be a
4. Each in man contains about eight hundred or more long coiled, minute tubules called seminiferous tubules.
5. The intimate mechanical and
physiological connection between fetal and maternal tissue is provided by
6. A cord containing blood vessels which connect the placenta with the fetus is called.
7.0n an average the length of menstrual cycle in females is completed in days.
8. A person infected with AIDS loses his
9. Male gamete fuse with ovule to form
10. The period of sexual maturity in human beings called
Answer:
1. spores
2. binary fission
3. hermaphrodite
4. testis
5. placenta
6. umbilical cord
7. 28
8. immunity
9. zygote
10. puberty

Question 40.
What is ‘after-birth’?
Answer:
About 15 minutes after the delivery of the baby, the placenta detaches from the uterine wall and is expelled out as ’after-birth’.

Question 41.
The lungs of the foetus are filled with fluid so it cannot breathe. But it doesn’t feel breathlessness. Why?
Answer:
A special tissue develops between uterine wall and the embryo called placenta. The growing foetus gets nutrients and oxygen from the mother’s blood through the placenta and umbilical cord. So it doesn’t feel breathlessness.

Question 42.
How is the structure of sperms adapted for fertilization?
Answer:
The vibrating tail of sperm helps to reach up to to ovum. The mitochondria present in the sperm provides energy for this movement. The enzyme produced by the acrosome present on the head of the sperm helps the sperm nucleus in penetrating the sheath of the ovum and entering the. ovum.

You can Download Equal Triangles Questions and Answers, Activity, Notes, Kerala Syllabus 8th Standard Maths Solutions Chapter 9 help you to revise complete Syllabus and score more marks in your examinations.

Kerala State Syllabus 8th Standard Maths Solutions Chapter 9 Negative Numbers

Negative Numbers Text Book Questions and Answers

Textbook Page No 165

Negative Numbers Class 8 Kerala Syllabus Question 1.
Using the principles above, compute the following:
i. 5 – 10
ii. -10 + 5
iii. -5 – 10
iv. -5 – 5
vi. \(-\frac{1}{2}+1 \frac{1}{2}\)
vii. \(-\frac{1}{2}-1 \frac{1}{2}\)
viii. \(-\frac{1}{2}+\frac{1}{2}\)
Solution:
i. 5 – 10 = – (10 – 5) = -5
(since for x – y = -(y – x ))

ii. – 10 + 5 = 5 – 10 = – (10 – 5) = -5
(since for -x + y = y – x and x – y = – (y – x))

iii. -5 – 10 = – (5 + 10 ) = -15
(since for – x – y = -(x + y))

iv. -5 – 5 = – (5 + 5) = -10
(since for -x – y = -(x + y))

v. -5 + 5 = 5 – 5 = 0
(since for -x + y = y – x)

Kerala Syllabus 8th Standard Maths Notes Pdf Question 2.
Take as x different positive numbers, negative numbers and zero, and compute x + 1, x – 1, 1 – x. Check whether the equations below hold for all numbers.
i. (1 + x) + (1 – x) = 2
ii. x – (x – 1) = 1
iii. 1 – x = -(x – 1)
Solution:
If x = 1
x + 1 = 1 + 1 = 2
x – 1 = 1 – 1 = 0
1 – x = 1 – 1 = 0
If x = 2
x + 1 = 2 + 1 = 3
x – 1 = 2 – 1 = 1
1 – x = 1 – 2 – 1
If x = o
x + 1 = 0 + 1
x – 1 = 0 – 1 = -1
1 – x = 1 – 0 = 1
If x =-1
x + 1 = -1 + 1 = 1 – 1 = 0
x – 1 = -1 – 1 = -2
1 – x = 1 – (-1) = 1 + 1 = 2
If x = -2
x + 1 = -2 + 1 = -1
x – 1 = -2 – 1 = -3
1 – x = 1 – (-2) = 1 + 2 = 3

i. (1 + x) + (1 – x)
In x = 1, (1 + x) + (1 – x) = 2 + 0 = 2
In x = 2, (1 + x) + (1 – x) = 3 + (-1) = 3 – 1 = 2
In x = o, (1 + x) + (1 – x) = 1 + 1 = 2
In x = -1, (1 + x) + (1 – x) = 0 + 2 = 2
In x – 2, (1 + x) + (1 – x) – 1 + 3 = 3 – 1 = 2
(1 + x) + (1 – x) = 2 , for all values of x

ii. x – (x – 1)
In x = 1, x – (x – 1) = 1 – 0 = 1
In x = 2, x – (x – 1) = 2 – 1 = 1
In x = o, x – (x – 1) = 0 – (-1) = 1
In x = -1, x – (x – 1) = -1 – (-2) = -1 + 2 = 1
In x =-2, x – (x – 1) = -2 – (-3) = -2 + 3 = 1
x – (x – 1) = 1, for all values of x

iii. 1 – x
In x = 1, 1 – x = o = -(x – 1)
In x = 2, 1 – x = -1 = -(1) = -(x – 1)
In x = o, 1 – x = 1 = -(-1) = -(x – 1)
In x = -1, 1 – x = 2 = -(-2) = -(x – 1)
In x = -2, 1 – x = 3 = -(-3) = -(x – 1)
1 – x = -(x – 1), for all values of x

Hsslive Guru Maths 8th Standard Kerala Syllabus Question 3.
Taking different numbers as x, y and compute x + y, x – y. Check whether the following hold for all kinds of numbers.
i. (x + y) – x = y
ii. (x + y) – y = x
iii. (x – y) + y = x
Solution:
If we take x = 6 and y = 2, x + y = 6 + 2 = 8 and x – y = 6 – 2 = 4
If x = -6 and y = 2, x + y = -6 + 2 = -4 and x – y = -6 – 2 = -8
If x = 6 and y = -2, x + y = 6 + (-2) = 4
and x – y = 6 – (-2) = 8
If x = -6 and y = -2, x + y = (-6) + (-2)
= -8 and x – y = (-6) – (-2 ) = -4

i. (x + y) – x
If x = 6 and y = -2, (x + y) – x
= 8 – 6 = 2 = y
If x = -6 and y = 2, (x + y) – x
= -4 – (-6) = -4 + 6 = 2 = y
If x = 6 and y = -2, (x + y) – x
= 4 – 6 = – 2 = y
If x = -6 and y = -2, (x + y) – x
= -8 – (-6) = -8 + 6 = -2 = y
(x + y) – x = y, for all values of x and y

ii. (x + y) – y
If x = 6 and y = 2, (x + y) – y
= 8 – 2 = 6 = x
If x = -6 and y = 2, (x + y) – y
= -4 – 2 = -6 = x
If x = 6 and y = -2, (x + y) – y
= 4 – (-2) = 4 + 2 = 6 = x
If x = -6 and y = -2, (x + y) – y
= -8 – (-2) = -8 + 2 = -6 = x
(x + y) – y = x, for all values of x and y

iii. (x – y) + y
If x = 6 and y = 2, (x – y) + y
= 4 + 2 = 6 = x
If x = -6 and y = 2, (x – y) + y
= -8 + 2 = -6 = x
If x = 6 and y = -2, (x – y) + y
= 8 + (-2) = 8 – 2 = 6 = x
If x = -6 and y =- 2, (x – y) + y
= -4 + (-2) = -6 = x
(x – y) + y = x, for all values of x and y

8th Standard Maths Notes Kerala Syllabus Question 4.
Check whether the equation are identities. Write the patterns got from each, on taking x = 1, 2, 3, 4, 5 and x = -1, -2, -3, -4, -5.
i. -x + (x + 1) = 1
ii. -x + (x + 1) + (x + 2) – (x + 3) = o
iii. -x – (x + 1) + (x + 2) + (x + 3) = 4
Solution:
i) -x + (x + 1) = 1
If x = 1, -x + (x + 1)
= -1 + (1 + 1) = -1 + 2 = 1
If x = 2, -x + (x + 1)
= -2 + (2 + 1) = -2 + 3 = 1
If x = 3, -x + (x + 1)
= -3 + (3 + 1) = -3 + 4 = 1
If x = 4 -x + (x + 1)
= 4 + (4 + 1) = -4 + 5 = 1
If x = 5, -x + (x + 1)
= -5 + (5 + 1) = -5 + 6 = 1
If x = -1, -x + (x + 1)
= -(-1) + (-1 + 1) = 1 +0 = 1
If x = -2, -x + (x + 1)
= -(-2) + (-2 + 1) = 2 + (-1) = 1
If x = -3, -x + (x + 1)
= -(-3) + (-3 + 1) = 3 + (-2) = 1
If x = -4, -x + (x + 1)
= -(-4) + (-4 + 1) = 4 + (-3) = 1
If x = -5, -x + (x + 1)
= -(-5) + (-5 + 1) = 5 + (-4) = 1
It is an identity.

ii. -x + (x + 1) + (x + 2) – (x + 3) = 0
If x = 1, -x + (x + 1) + (x + 2) – (x + 3)
= -1 + (1 + 1) + (1 + 2) – (1 + 3)
= -1 + 2 + 3 – 4 = 0
If x = 2, -x + (x + 1) + (x + 2) – (x + 3)
= -2 + (2 + 1) + (2 + 2) – (2 + 3)
= -2 + 3 + 4 – 5 = 0
If x = 3, -x + (x + 1) + (x + 2) – (x + 3)
= -3 + (3 + 1) + (3 + 2) – (3 + 3)
= -3 + 4 + 5 – 6 = o
If x = 4 -x + (x + 1) + (x + 2) – (x + 3)
= -4 + (4 + 1) + (4 + 2) – (4 + 3)
= -4 + 5 + 6 – 7 = 0
If x = 5, -x + (x + 1) + (x + 2) – (x + 3)
= -5 + (5 + 1) + (5 + 2) – (5 + 3)
= -5 +6 +7 -8= 0
If x = -1, -x + (x + 1) + (x + 2) – (x + 3)
= -(-1) + (-1 + 1) + (-1 + 2) – (-1 + 3)
= 1 + 0 + 1 – 2 = 0
If x = -2, -x + (x + 1) + (x + 2) – (x + 3)
= 2 + (-2 + 1) + (-2 + 2) – (-2 + 3)
= 2 + -1 + 0 – 1 = 0
If x = -3, -x + (x + 1) + (x + 2) – (x + 3)
= 3 + (-3 + 1) + (-3 + 2) – (-3 + 3)
= 3 + -2 + -1 – 0 = 0
If x = -4, -x + (x + 1) + (x + 2) – (x + 3)
= 4 + (-4 + 1) + (-4 + 2) – (-4 + 3)
= 4 + -3 + -2 – (-1) = 0
If x = -5, -x + (x + 1) + (x + 2) – (x + 3)
= 5 + (-5 + 1) +(-5 + 2) – (-5 + 3)
= 5 + -4 + -3 – (-2) = o
It is an identity.

iii. -x – (x + 1) + (x + 2) + (x + 3) = 4
If x = 1, -x – (x +1) + (x + 2) + (x + 3)
= -1 – (1 + 1) + (1 + 2) + (1 + 3)
= -1 – 2 + 3 + 4 = 4
If x = 2, -x – (x + 1) + (x + 2) + (x + 3)
= -2 – (2 + 1) +(2 + 2) + (2 + 3)
= -2 – 3 + 4 + 5 = 4
If x = 3, -x – (x + 1) + (x + 2) + (x + 3)
= -3 – (3 + 1) + (3 + 2) + (2 + 3)
= -3 – 4 + 5 + 6 = 4
If x = 4 -x – (x + 1) + (x + 2) + (x + 3)
= -4 – (4 + 1) + (4 + 2) + (4 + 3)
= -4 – 5 + 6 + 7 = 4
If x = 5, -x – (x + 1) + (x + 2) + (x + 3)
= -5 – (5 + 1) + (5 + 2) +(5 + 3)
= -5 – 6 + 7 + 8 = 4
If x = -1, -x – (x + 1) + (x + 2) + (x + 3)
= -(-1) – (-1 + 1) + (-1 + 2) + (-1 + 3)
= 1 – 0 + 1 + 2 = 4
If x = -2, -x – (x + 1) + (x + 2) + (x + 3)
= 2 – (-2 + 1) + (-2 + 2) + (-2 + 3)
= 2 – (-1) + 0 + 1 = 4
If x = -3, -x – (x + 1) + (x + 2) + (x + 3)
= 3 – (-3 + 1) + (-3 + 2) + (-3 + 3)
= 3 – (-2) + – 1 + 0 = 4
If x = -4, -x – (x + 1) + (x + 2) + (x + 3)
= 4 – (-4 + 1) + (-4 + 2) + (-4 + 3)
= 4 – (-3) + – 2 + (-1) = 4
If x = -5, -x – (x + 1) + (x + 2) + (x + 3)
= 5 – (-5 + 1) + (-5 + 2) + (-5 + 3)
= 5 – (-4) + -3 + (-2) = 4
It is an identity.

Kerala Syllabus 8th Standard Maths Notes Question 5.
Taking different numbers, positive, negative and zero, as x, y, z and compute x + (y + z) and (x + y) + z. Check whether the equation, x + (y + z) = (x + y) + z holds for all these numbers.
Solution:

Textbook Page No 178

Class 8 Maths Kerala Syllabus Question 6.
Take various positive and negative numbers as x, y, z and compute (x + y) z and xz + yz. Check whether the equation (x + y) z = xz + yz holds for all these.
Solution:

Kerala Syllabus 8th Standard Maths Guide Question 7.
In each of the following equations, take x as the given numbers and compute the numbers y.
i. y = x², x = -5, x = 5
ii. y = x² + 3x + 2, x = -2
iii. y =x² + 5x + 4, x = -2, x = -3
iv. y = x³ + 1, x = -1
v. y = x³ + x² + x + 1
Solution:
i. y = x² , x = -5 , x = 5
If x =-5, y = x² = (-5 )² = -5 × -5 = 25
If x = 5, y = x² = (5)² = 5 × 5 = 25

ii. y = x² + 3x + 2, x = -2
If x = -2, y = x² + 3x + 2 = (-2)² + 3x(-2) + 2
= 4 – 6 + 2 = -2 + 2 = 0

iii. y = x² + 5x + 4, x = -2 , x = -3
If x = -2, y = x² + 5x + 4 = (-2 )² + 5x(-2) + 4
= 4 – 10 + 4 = -6 + 4 = -2
If x = -3, y = x² + 5x + 4 = (-3)² + 5x(-3) + 4
= 9 – 15 + 4 = -6 + 4 = -2

iv. y = x³ + 1, x = -1
If x = -1, y = x³ + 1 = (-1 )³ + 1
= (-1)(-1)(-1) + 1 = 1 × (-1) + 1 = 0

v. y = x³ + x² + x + 1, x = -1
If x = -1, y = x³ + x² + x + 1 = (-1)³ +(-1)² + (-1) + 1 = -1 + 1 – 1 + 1 = o

Kerala Syllabus 8th Standard Maths Question 8.
For a point starting at a point P and travelling along a straight line, time of travel is taken as t and the distance from P as s. The relation between s and t is found to be s = 12t – 2t², where distances to the right are taken as positive numbers and to the left as negative numbers.
i. Is the position of the point to the right or left of P, till 6 seconds?
ii. Where is the position at 6 seconds?
iii. After 6 seconds?
(Here it is convenient to write 12t – 2t² = 2t(6 – t).
Solution:
i. S = 12t – 2t²
Distance to the point when time is 1 second = 12t – 2t² = 12 × 1 – 2 × 1² = 12 – 2 = 10 m
Distance to the point when time is 5 second = 12t – 2t² = 12 × 5 – 2 × 5² = 60 – 50 = 10 m
Since the distance to the point till 6 seconds is positive. So the position of the point is on the right of P.
ii. Distance to the point when time is 6 second = 12t – 2t² = 12 × 6 – 2 × 62 = 72 – 72 = o
At the 6^th second, the point is at P.
iii. Distance to the point when time is 7 second (after 6 sec)= 12t – 2t² = 12 × 7 – 2 × 7²
= 84 – 2 × 49 = 84 – 98 = -14 metres
This is a negative number, So the position of the point is on the left of P.

Textbook Page No 179

8th Std Maths Guide Kerala Syllabus Question 9.
Natural numbers, their negatives and zero are together called integers. How many pair of integers are there, satisfying the equation. x² + y² = 25?
Solution:
It is convenient to write it as a table

Textbook Page No 180

Kerala Syllabus 8th Standard Maths Notes Malayalam Medium Question 10.

Solution:

Class 8 Kerala Syllabus Maths Question 11.

Solution:

Class 8 Maths Scert Solutions Kerala Syllabus Question 12.
In the equation \(z=\frac{x}{y}-\frac{y}{x}\), take x as the numbers given below and calculate the number z.
i. x = 10, y = -5
ii. x = -10, y = 5
iii. x = -10, y = -5
iv. x = 5, y = -10
v. x = -5, y = 10
Solution:

Additional Questions and Answers

Maths Class 8 Kerala Syllabus  Question 1.
Match the following

Solution:

8th Class Maths Notes Kerala Syllabus Question 2.

Solution:

Question 3.
Which of the following number is the largest (-1)⁶, (-1)¹⁰, (-1)², (-1)⁵⁰
Solution:
If the power of (-1) is even then answer will be 1
If the power of (-1) is odd then answer will be -1
(-1)⁶ = 1
(-1)¹⁰ = 1
(1)² = 1
(-1)⁵⁰ = 1
All the given numbers are equal.

Question 4.

Solution:

Question 5.
Complete the following table

Solution:

Question 6.
Write whether the answer got on doing the following operations are positive number or negative number.

Solution:

Question 7.

Solution:

Question 8.

Solution:

Question 9.
Calculate (-1)¹⁰ + (-1)¹⁷ + (-1)²¹ + (-1)²⁶ + (-1)⁷⁷
Solution:
(-1)¹⁰ + (-1)¹⁷ + (-1)²¹ + (-1)²⁶ + (-1)⁷⁷
= 1 + (-1) + (-1) + 1 + (-1)
= 1 – 1 – 1 + 1 – 1 = 2 – 3 = -1

Question 10.
Simplify [(-4) × (-5)] + [-16 × \(\frac{-1}{2}\) ]
Solution:
-4 × -5 = 20

Question 11.
If x = 8 and y = -3; find the values of x + y, y + x, x – y, y – x, -x – y and – y – x
Solution:
x + y = 8 + -3 = 5
y + x = -3 + 8 = 5
x – y = 8 – (-3) = 8 + 3 = 11
y – x = -3 – 8 = -11
– x – y = -8 – (-3) = -8 + 3 = -5
-y – x = -(-3) – 8 = 3 – 8 = -5

Question 12.
If x = 7, y = -6 and z = -2, find the value of
i. (x + y) + z
ii. x + (y + z)
iii. xyz
iv. (x + y)z
v. xy + xz
Solution:
i. (x + y) + z = (7 + -6) + -2 = 1 – 2 = -1
ii. x + (y + z) = 7 + (-6 + -2)
= 7 – 8 = -1
iii. xyz = 7 × -6 × -2 = 84
iv. (x + y)z = (7 + -6) × -2
= 1 × -2 = -2
v. xy + xz = (7 × -6) + (7 × -2)
= -42 – 14
= -56

Question 13.
Compute y = x² + 9x – 5, for take x as the given number,
i. x = 5
ii. x = -2
iii. x = o
iv. x = -3
Solution:
i. x = 5
y = x² + 9x – 5
= 5² + 9 × 5 – 5 = 25 + 45 – 5
= 20 + 45 = 65

ii. x = -2
y = x² + 9x – 5
=(2)² + 9 × (-2) -5
= 4 – 18 – 5 = 4 – 23 = – 19

iii. x = 0
y = x² + 9x – 5
= 0 + 9 × 0 – 5 = -5

iv. x = -3
y = x² + 9x – 5
= (-3)² + 9 × (-3) – 5
= 9 – 27 – 5 = 9 – 32 = -23

Question 14.
Find y = x⁴ + x³ + x² + x + 1, If x = -1
Solution:
y = x⁴ + x³ + x² + x + 1
= (-1)⁴ + (-1)³ + (-1)² + (-1) + 1
= 1 + (-1) + 1 + (-1) + 1
= 1 – 1 + 1 – 1 + 1
= 0 + 0 + 1 = 1

Question 15.
Complete the table

Solution:

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Kerala State Syllabus 8th Standard Hindi Solutions Unit 4 Chapter 2 इस बारिश में

इस बारिश में पाठ्यपुस्तक के प्रश्न और उत्तर

इस बारिश में कविता Kerala Syllabus 8th Chapter 2 प्रश्ना 1.
‘उसी के पास अब मेरी / बारिश भी चली गई’ से आपने क्या समझा?

उत्तर:
यह एक किसान का रोदन है। यह रोदन किसान की हालत की ओर संकेत करता – है। आजकल किसानों की ज़मीन छीन ली जाती है। यहाँ किसान यह व्यक्त करता है कि ज़मीन के साथ बारिश भी चली गई है। यहाँ खेती और बारिश के घने संबंध स्पष्ट होते हैं।

Is Barish Mein Kerala Syllabus 8th Chapter 2 प्रश्ना 2.
जिसकी नहीं कोई ज़मीन/उसका नहीं कोई आसमान’ इन पंक्तियों का क्या तात्पर्य है?

उत्तर:
इन पंक्तियों का मतलब है कि किसानों का ज़मीन से अटूट संबंध है। ज़मीन नष्ट होने पर किसान का अस्तित्व नष्ट हो जाता है। यह उस से जीने के सब सपने नष्ट हो जाते हैं।

इस बारिश में Textbook Activities

इस बारिश में कविता Meaning In Malayalam Chapter 2 प्रश्ना 1.
कविता में ‘उसी के लिए’ दोहराया गया है। यह प्रयोग किन-किन की ओर संकेत करता है?

उत्तर:
किसानों का शोषण करनेवालों की ओर यहाँ संकेत है।

इस बारिश में कविता का सारांश Kerala Syllabus 8th Chapter 2 प्रश्ना 2.
‘हल नहीं / बैल नहीं’ -इसमें ‘हल’ और ‘बैल’ किन-किनके प्रतीक हैं?

उत्तर:
हल’ और ‘बैल’ खेती और किसानी ज़िंदगी के प्रतीक हैं।

Hss Live Guru 8 Hindi Kerala Syllabus Chapter 2  प्रश्ना 3.
निम्नलिखित आशयवाली पंक्तियाँ चुनकर लिखें।

फसल होने पर कर्ज चुकाने की किसान की झूठी प्रतीक्षा भी नहीं रह गई।

उत्तर:
अगली फसल होते ही सब चुकता कर दूंगा/अब तो मेरी झूठी/ये गुज़ारिश भी चली गई।

Hss Live Guru 8th Hindi Kerala Syllabus Chapter 2 प्रश्ना 4.
आस्वादन टिप्पणी तैयार करें।

उत्तर:
नरेश सक्सेना समकालीन हिंदी कविता के समर्पित कार्यकर्ताओं की अग्रिम पंक्ति में हैं। ‘इस बारिश में’ नामक कविता में किसान की ज़मीन छीन जाने की कथा है। यह एक किसान का बारिश के मौसम का शोकगीत है। आकाश में कई दूर छा जानेवाले बादलों को देखकर किसान आह भरता है। अपनी ज़मीन छिन जाने पर किसान खेती न कर सकता। भूमंडलीकरण के दौर के किसानों की सिसकियाँ यहाँ हम देख सकते हैं। इस कविता क द्वारा कवि किसान लोगों की त्रासदी की ओर हमारा ध्यान आकर्षित करते हैं। कवि का कहना है कि अब बारिश भी ज़मीन के पीछे चली गई है। धरती की छाती से सौंधी सुगंध भी छिन गई मिट्टी के लिए उठती है।

अब किसान के लिए हल और बैल नहीं, खेतों के बीच का रास्ता नहीं, कहीं हरियाली की बूंद भी दिखाई न देता। किसान के जीवन का ताल, प्रतीक्षा का नक्षत्र सब नष्ट हो चुकी है। फसल होने पर कर्ज चुकाने की किसान की प्रतीक्षा भी नहीं रह गई। किसान की अपनी खेत – खलिहानों से दूर रहने की विवशत इस कविता में हम देख सकते हैं। ज़मीन छिन जाने पर किसान भयानक शोषण का शिकार बन जाता है। कवि . इस कविता दवारा यही कहना चाहता है। एक कविता तभी समसामयिक मानी जाती है जब वह तत्कालीन समस्याओं का
संबोधन करती है। इस बारिश में’ नामक यह कविता इस कसौटी पर खरा उतरता है।

इस बारिश में Summary in Malayalam and Translation

इस बारिश में शब्दार्थ Word meanings

You can Download Reflection of Light in Spherical Mirrors Questions and Answers, Summary, Activity, Notes, Kerala Syllabus 8th Standard Basic Science Solutions Chapter 18 help you to revise complete Syllabus and score more marks in your examinations.

Kerala State Syllabus 8th Standard Basic Science Solutions Chapter 18 Reflection of Light in Spherical Mirrors

The phenomena of light is always a surprising one. From long time ago man has tried to study about light. This chapter explains to draw the figure of the images formed by mirrors, their uses, magnification etc.

Reflection Of Light In Spherical Mirrors Class 8 Notes Spherical mirrors

Images are formed not only in-plane mirrors but also in smooth curved surfaces. Spherical mirrors are mirrors in which the reflecting surface is a part of the sphere. The center of a sphere of which the mirror is a part is the center of curvature. Any I line drawn from the center of curvature to the mirror is normal to the mirror. Radius of curvature of a mirror is the radius of the sphere of which is a part. The reflecting surface of the mirror is called the aperture of a mirror. The midpoint of the reflecting surface is called the pole. The straight line connecting the pole and center of curvature of a mirror is the principal axis of the mirror.

The angle of incident and angle of reflection are equal in spherical mirrors. Rays of light incident on a concave mirror, parallel to the principal axis, passes through a fixed point on the principal axis after reflection. This point is the principal focus of the concave mirror. Rays of light incident on a convex mirror parallel to the principal axis appear to come from a fixed point on the other side of the mirror. The point is the principal axis of the convex mirror.

Focal length of a mirror is the distance from pole of the mirror and the principal’s focus of the mirror. Rays of light coming from infinity get focused on a plane perpendicular to the principal axis. This plane is the focus plane. The focus plane passes through the focus plane.

Reflection Of Light In Spherical Mirrors Class 8 Images formed by spherical mirrors

The image of an object placed different positions in front of a mirror is.formed in different positions. Rays of light incident on a concave mirror, parallel to the principal axis, passes through a fixed point on the principal axis after reflection Rays incident on an a concave mirror through the principal focus are reflected parallel to the principal axis.

Rays incident through the center of curvature reflected through the same path. Rays incident on the pole makes an angle with the principal axis. The ray diagrams of images formed by spherical mirrors are drawn according to the above rules. An object placed between F and C in front of a concave mirror, the image will be real and inverted. If the object is at F the image is formed at infinity. The paths of reflected rays are parallel to each other. If the object is in between F and P the image is formed behind the mirror. The image is erect and virtual.

Reflection Of Light In Spherical Mirrors 8th Magnification

Magnification is the ratio of the height of the image to the height of the object.

Reflection Of Light In Spherical Mirrors Class 8 Notes Pdf Uses of spherical mirrors

Spherical mirrors are used in lighthouses and reflectors.

Reflection of Light in Spherical Mirrors Textbook Questions and Answers

Class 8 Physics Notes Kerala Syllabus Questions 1.
Classify the following statements as to those related to concave mirrors and convex mirrors and tabulate them accordingly.
a. to view the face
b. as makeup mirror
c. as rearview mirrors in vehicles
d. in solar concentrators
e. in periscopes
f. as shaving mirror
Answer:
Concave mirror:

• In solar concentrators
• Makeup mirror
• Shaving mirror

Convex mirror:

• In rearview mirrors of vehicles
• In Searchlights

Plane mirror:

• In periscopes
• To see face

8th Class Physics Notes Pdf Question 2.
Calculate the radius of curvature of a convex mirror of focal length 12 cm.
Answer:
focal length of the mirror = 12 cm
\(\mathrm{f}=\frac{\mathrm{R}}{2} \quad 12=\frac{\mathrm{R}}{2}\)
R = 2 × 12 = 24 cm

Reflection Of Light At Curved Surfaces Questions And Answers 8th Question 3.
A ray of light is made to fall on the pole of a concave mirror making an angle 30° with the principal axis.
a. What is the angle of reflection?
b. Justify your answer.
c. Draw the ray diagram.
Answer:
a. Angle of reflection is 30°
b. angle of incidence and angle of reflection are equal
c. the figure showing angle of incidence and angle of reflection is 210°

Chemistry Class 8 Kerala Syllabus Question 4.
Which type of mirror always gives an erect and diminished image?
Answer:
Convex mirror

Kerala Syllabus 8th Standard Chemistry Notes Question 5.
A ray of light incident on a spherical mirror gets reflected along the same path. If so, show the light incident on the mirror.
Answer:

8th Class Biology Notes Pdf Question 6.
OA is a ray of light incident on a concave mirror.
a. Draw the path of the reflected ray

b. On what basis did you mark the reflected ray?
Answer:

b. In mirrors angle of incidence and angle of reflection are same. The normal to the point of incidence is passed through the center of curva¬ture. The angle between ray of reflection and the normal is the same as angle of incidence.

8th Class Biology Notes Pdf Malayalam Medium Question 7.
Write down the type of mirrors that should be used for getting the following type of images.
a. real and magnified
b. virtual and magnified
c. virtual and diminished
d. real and diminished
Answer:
a. concave mirror
b. concave mirror
c. convex mirror
d. concave mirror

Kerala Syllabus 8th Standard Chemistry Notes Malayalam Medium Question 8.
The height of an object kept 12 cm away from a concave mirror is 1 cm. Calculate the magnifica¬tion if an image of height 2.5 cm is formed in front of the mirror.
Answer:

8th Standard Chemistry Textbook Question 9.
Which type of mirror always gives a virtual and erect-image, b. Is this image magnified or diminished?
Answer:
a. convex mirror
b. Diminished

Reflection of Light in Spherical Mirrors Additional Questions and Answers

8th Class Biology Notes Pdf Kerala Syllabus Question 1.
Complete the table

Answer:
a. 30°
b. 40°
c. 50°
d. 60°

Kerala Syllabus 8th Standard Physics Notes Question 2.
If the radius of curvature of a concave mirror is 24 cm what is its focal length?
Answer:
R = 24 cm

8th Standard Chemistry Textbook Kerala Syllabus Question 3.
Find the radius of curvature of a convex mirror of focal length 0.6 m
Answer:

Basic Science Class 8 Solutions Question 4.
Write the characteristics of the image formed by an object plac¬ed at the center of curvature of a concave mirror?
Answer:
Position: At the center of curvature at the same side
Size : Same as the size of the object Nature: Real, Inverted

Reflection Of Light By Spherical Mirrors 8th Question 5.
Complete the figure

Answer:

Hsslive Guru Physics 8th Standard Question 6.
Complete the table

Answer:
a. Passes through principal focus
b. Seem to come from the principal focus
c, d. Returns parallel to the principal axis
e, f. Returns through the same path
g, h. Reflects in the same angle of incident ray.

Question 7.
Write three differences of real image and virtual image which is made by spherical mirrors
Answer:
Real image:

1. Inverted
2. can be shown on the screen
3. can measure the length of the image and distance to the image

Virtual image:

1. Cannot show on the screen
2. Cannot measure
3. Erect

Question 8.
Write uses of concave mirrors
Answer:

•  As shaving mirror
• As makeup mirror
• As head mirrors used by doctors
• In film projectors

Question 9.
Examine the position off the object given in the figure and table the following peculiarities

a. position of the image
b. size of the image
c. nature of the image
Answer:
a. Behind the mirror.
b. Larger than the object.
c. Erect and virtual

Question 10.
When an object of height 4 cm is placed in front of a concave mirror an image of height 8cm is formed. Find magnification.
Answer:
h_i = 4cm h_o= -8 cm
Magnification = \(\frac{h_{i}}{h_{0}}\) = \(\frac{h_{-8}}{h_{4}}\) = -2

Question 11.

a. Examine the figure and find the magnification
b. What is the height of the object if height of the image is 4cm when the object is placed on the same position in front of the mirror.
Answer:

Question 12.
Write the uses of convex mirror
Answer:

• As reflector in the street light
• As rearview mirror
• In searchlights

You can Download Metals Questions and Answers, Summary, Activity, Notes, Kerala Syllabus 8th Standard Basic Science Solutions Chapter 7 help you to revise complete Syllabus and score more marks in your examinations.

Kerala State Syllabus 8th Standard Basic Science Solutions Chapter 7 Metals

Metals have some general charac-teristics. They are thermal conductors and electrical conductors. Metals can be beaten into thin sheets by hammering (malleability). Metals can be drawn into thin fine wires (ductility). Hardness is yet another property of metals. The surface newly formed when metals are cut, has a shining appearance (metallic lustre) Metals have the ability to produce sound when tapped with a hard material (sonority).

Metals have high melting point and density. Making use of these characteristics of metals they are used in various purposes. Metals are used to make electric wire because of its electrical conductivity. They are used to make utensils as the metals are thermal conductors. Metals have high density. So they are used to make farming tools. The sonority of metal is utilised to make bells in the places of worship.

There are some similarities in chemical properties of metals. Almost all the metals get tarnished when they are exposed to air for some days. This is because they are react with various components of atmospheric air.

Metals react with water. Metals like sodium, potassium etc reacts with cold water to liberate hydrogen.
Zinc, aluminium, iron, magnesium etc. react with dilute hydrochloric acid to form hydrogen along with salt of metal. There are some metals which does not react with acids.
Ex : Copper.

As the metals react with atmospheric air and water vapour causes corrosion. The iron reacts with air and water vapour. So it undergoes corrosion. Verdigris is formed on copper by reacting with the components of air. Iron and a number of other metals react with different components of air and form new products. This process is known as corrosion of metals. Painting on the metal, electroplating with non corrosive metals are some methods to prevent the corrosion

Metals Textbook Questions and Answers

Kerala Syllabus 8th Standard Chemistry Notes Question 1.
Some metals are listed below. Complete the table by identifying the different uses and the properties which are responsible for the same.

Answer:

Hss Live Guru 8 Chemistry Kerala Syllabus Question 2.
Iron is a metal which corrodes fast.
a. What are the factors that favour the corrosion of iron?
b. In coastal regions, copper nails are preferred to iron nails. What could be the reason?
c. Can you suggest some measures to prevent the corrosion of iron?
Answer:
a. Air and water vapour in the atmo sphere
b. Iron rod corrodes quickly in salt water
c. Painting on the metal, electroplating with non corrosive metals

Hsslive Guru Chemistry 8 Kerala Syllabus Question 3.
Based on the physical properties of metals, indicate whether the following statements are true or false

1. Aluminium is a conductor of electricity.
2. The metal caesium melts at high temperatures.
3. Platinum is a metal with poor malleability.
4. Potassium is a hard metal.
5. Copper, metal is sonorous.
6. The density of gold is very low.
7. Copper is a good conductor of heat.
8. Sodium is a hard metal.
9. One of the reasons for the use of gold in making ornaments is its metallic lustre.
10. The ductility of tungsten is high.

Answer:

1. true
2. false
3. true
4. false
5. true
6. false
7. true
8. false
9. true
10. true

Hsslive Guru 8th Basic Science Kerala Syllabus Question 4.
Which among the metals is stored in kerosene?
(a) Sodium
(b) Iron
(c) Tungsten
(d) Chromium
Why is it stored in kerosene?
Answer:
a. Sodium. Becuase they vigorously react with air.

Kerala Syllabus 8th Standard Physics Notes Question 5.
The names of some metals are given below.
Tungsten, Gold, Sodium, Copper, Iron, Magnesium
Answer the following questions by selecting the appropriate ones from the list.

• Which metal with high malleability is used for making ornaments?
• Which of these metals reacts with cold water?
• Which of these is a hard metal but corrodes easily?

Answer:

• Gold
• Sodium
• Iron

Hsslive Guru Chemistry Class 8 Kerala Syllabus Question 6.
Give reasons for the following statements.

• Tamarind is not stored in aluminium vessels.
• It is a common practice to apply oil on iron articles and tools.
• Stainless steel knives, instead of iron knives, are preferred for cutting citrus fruits.

Answer:
a. Tamarind is acidic. So aluminium corrodes by reacting with acid
b.To reduce the contact with air
c. Gtrus fruit is acidic. It reacts with iron.

Hsslive Class 8 Chemistry Kerala Syllabus Question 7.
Connect a torch bulb to the battery with the different metal wires. Find out which wire gives the highest brightness to the bulb? Arrange the wires in the decreasing order of their electrical conductivity.
Answer:
Iron-copper-aluminium-nichrome

Hsslive.Guru Class 8 Kerala Syllabus Question 8.
Collect the following materials: an iron nail, an aluminium wire, a pencil lead, a copper Beat them hard using a hammer. Which of thenvCan he flattened? What is your conclusion from this experiment?
Answer:
Iron nail, aluminium wire. The metals have malleability.

Class 8 Physics Notes Kerala Syllabus Question 9.
You have understood the properties of metals. Find out the metals mentioned in the following cases.
a. Which metal is used in the storage batteries of vehicles?
b. Most of the metals are solids. Which metal exists as a liquid even at low temperatures?
c. Iron articles are coated with other metals to protect them from corrosion. Which are the two metals usually used for this purpose?
d. Metals have high density. Which is the densest metal?
Answer:
a. zinc
b. mercury
c. zinc, magnesium
d. gold

Metals Additional Questions and Answers

Hsslive 8 Chemistry Kerala Syllabus Question 1.
Tabulate the general properties of metals
Answer:
Hardness, High density, Ductility, Malleability, Sonority, Thermal conductivity, Electrical conductivity.

Hss Live Guru 8 Kerala Syllabus  Question 2.
List some of the general properties of metals.
Answer:
Generally metals, are good conductors of electricity, are good conductors of heat, are malleable (can be hammered into thin sheets), are ductile (can be pulled into wires), are solids (except mercury), are hard and strong, have metallic lustre, have high densities, have high melting points, have high boiling points

Hss Live Guru Class 8 Kerala Syllabus Question 3.
What are the situation make use of the following properties of metals Hardness, malleability, thermal conductivity, electrical conductivity, ductility
Answer:
To make farming tools
• To make aluminium foil,
• To make utensils
• To make electrical equipments
• To make ornaments

Hss Live Guru 8th Chemistry Kerala Syllabus Question 4.
Write the following metals in the ascending order of electrical conductivity. Silver, copper, aluminium
Answer:
Aluminium, copper, silver

Hsslive Guru 8th Class Chemistry Kerala Syllabus Question 5.
Even though the electric conductivity is less the wires on electric posts are made up of aluminium. Why?
Answer:
Due to less weight and cost.

Question 6.
Which metal is seen in liquid state?
Answer:
Mercury

Question 7.
Fill the table

Answer:

Question 8.
Butter milk is not kept in aluminium vessels. Why?
Answer:
Butter milk is acid. So it reacts with aluminium

Question 9.
What are the two things which are caused to form verdigris on copper?
Answer:
Air and water vapour

Question 10.
Select the metals which do not react with air.
Copper, iron, gold, magnesium, platinum, sodium, silver
Answer:
Gold, silver, platinum

Question 11.
Write the following rentals in the ascending order of the reactivity with acids. Copper, sodium, iron, aluminium
Answer:
Sodium, iron, aluminium, copper

Question 12.
Why should we paint the iron bars of window?
Answer: To protect them from rusting

Question 13.
What are the components effecting rusting of iron?
Answer:
Air, moisture present in atmosphere

Question 14.
Why sodium and potassium are kept in kerosene?
Answer:
Because they vigorously react with air.

Question 15.
Aluminium vessels get tarnished after few days they purchased. Why?
Answer:
aluminium undergo chemical reaction with air and a covering is formed.

Question 16.
The window bars near sea shore undergo rusting quickly. Why?
Answer:
Iron react with saltwater quickly and undergo corrosion.

Question 17.
Which property of metals is used to make bells.
Answer:
Sonority

Question 18.
What is the property of metal caused for shining appearance?
Answer:
Metallic lustre.

Question 19.
Which is the metal used for making filament of bulb? Which property is made use of it.
Answer:
Tungsten; ductility.

Question 20.
Is there any advantage, if iron nails are kept inside kerosene. Why?
Answer:
Yes, it prevent rusting. Iron nails, when kept inside kerosene, are protected from rusting. They are not in contact with atmospheric air or moisture.

Question 21.
A bottle filled with quicklime is closed with a lid made of iron. After some days, when the lid is opened, which part of the lid is more rusted? What is the reason for that?
Answer:
The outer part of the lid is more rusted. The outer part is in contact with air and moisture; but due to the presence of quicklime, there is no water content inside.

Question 22.
Find the odd one out. Write the reason.
a. Iron, aluminium, sodium, copper
b. Silver, gold, sulphur, lead
Answer:
a. Sodium. Sodium is a soft metal while others are hard metals b. Sulphur. Sulphur is a non-metal others are metals.

Question 23.
Which are the metals found in free state! Why?
Answer:
Metals like gold, platinum, silver, copper etc. are found in free state, . because these metals do not react with air.

Question 24.
To prepare thin sheets, metals are beaten and made into thin sheets.
a. What is the name of this property of metals by which they can be beaten into thin sheets?
b. Which metals can be beaten and made into the thinnest sheet?
Answer:
a. Malleability
b. Gold

Question 25.
Among the statements given below which are true about metals.
a. Metals bum
b. Metals can be beaten into thin sheets.
c. Metals are dull in appearance.
d. Metals are good conductor of heat.
e. Metals conduct electricity.
f. Metals break into small pieces when struck with a hammer.
Answer:
b, d, and e

Question 26.
Does any immediate change occur when a bright nail is exposed to air? What happens to it after a few days?
Answer:
Tmmediate change does not occur. After a few days it reacts slowly with air and gets a coating of oxide.

Question 27.
Why are aluminium rods not used to reinforce concrete?
Answer:
Pure aluminium is thin, not sufficiently hard and strong. So aluminium rods are not used to reinforce concrete.

Question 28.
Iron made objects will undergo quick rusting. Give reason? What are the methods used to prevent the speed of the process?
Answer:
Tron became destroyed when it can react with atmospheric oxygen and moisture form hydrated iron oxide (rust)

• Painting, apply grease or oil
• Covered the iron by using highly active metals like zinc
• Apply tin on iron. ,
• Protect iron made object by applying nickel and chromium on it.

You can Download Chemical Change Questions and Answers, Summary, Activity, Notes, Kerala Syllabus 8th Standard Basic Science Solutions Chapter 6 help you to revise complete Syllabus and score more marks in your examinations.

Kerala State Syllabus 8th Standard Basic Science Solutions Chapter 6 Chemical Change

Chemical Changes Questions and Answers

All the changes in nature is divided into physical changes and chemical changes. During a physical change, only a change in the arrangement of molecules occurs. Hence it can be easily brought back to its original state. In the case of chemical changes, new molecules are formed.

The alkali formed by the reaction of sodium with water is sodium hydroxide. Because of its basic nature it becomes pink colour when phenolphthalein is added to it.

In the reaction of magnesium burns in air heat and light are produced.

Chemical Changes Class 8 Kerala Syllabus Thermo chemical reactions

The reaction of magnesium with dil. hydrochloric acid, hydrogen is produced and heat is evolved. So we feel hot when we touch the test tube.
Mg + 2HCl → MgCl₂ + H₂ + heat

Take a few crystals of potassium permanganate in a dry test tube. Heat the test tube. Bring a glowing incense stick to the mouth of the test tube. When potassium permanganate is heated, it decomposes to form potassium mangnate, manganese dioxide. and oxygen. In this reaction, potassium permanganate decomposes with absorption of heat and oxygen is evolved.

Add hydrochloric acid to a concentrated solution of sodium hydroxide taken in a test tube. Heat is evolved. Chemical reactions which liberate heat are called exothermic reactions and those which absorb heat are called endothermic reactions.

Chemical Changes Class 8 Notes Kerala Syllabus Photochemical reactions

Photosynthesis is a chemical reaction that is responsible for sustaining life on earth. In this reaction, plants produce glucose by absorbing light. Note the chemical equation of this reaction.
6 H₂ O + 6 CO₂ + Light → C₆ H₁₂ O₆ + 6 O₂

The glucose thus formed is stored by plants in the form of starch.

Take some silver bromide in watch glasses. That will change to black because silver is precipitated.

Chemical reactions which liberate or absorb light energy are known as photochemical reactions.

Chemical Changes Class 8 Kerala Syllabus Electrochemical reactions

The change in colour of copper sulphate solution and the deposition of copper at the electrode proves that a chemical change has occurred.

In this reaction, copper sulphate decomposed with the absorption of electrical energy. The process in which a substance undergoes decomposition by the absorption of electrical energy is known as electrolysis.

Here, electricity is produced as a result of a chemical reaction between the acid and the metals kept immersed in it. Such arrangements which produce electricity as a. result of chemical reaction are known as electrochemical cells.
We can make cells using a variety of fruits and different metals like zinc. Chemical reactions in which electrical energy is consumed or produced are known as electrochemical reactions.

Chemical Changes Standard 8 Kerala Syllabus Electroplating

You are familiar with the gold plated ornaments that are available in the market. Electricity is used to obtain a thin coating of a particular metal on other metallic objects. This process is called electroplating.

Now, you might have understood that forms of energy like heat, light and electricity are exchanged during chemical reactions. There are chemical reactions which involve the absorption or liberation of energy. Those which absorb energy are known as endoergic reactions and those which liberate energy are known as exoergic reactions.

Energy transfer occurs during any chemical reaction. A chemical reaction will be known based on the major energy form which gets absorbed or liberated.

Kerala Syllabus 8th Standard Chemistry Notes Different types of cells

The cells are the electric source commonly used. Following is the table of cells and their uses

Hsslive Guru Chemistry 8 Kerala Syllabus Environment friendly changes

Many natural and manmade chemical changes that occur around us are not nature – friendly. Nature tries its best to adapt these changes But after a limit it destroy the harmony of nature. The chemicals coming out from the factories will make the problem serious. Hence, accumulation of those materials, which cannot be biodegraded may become a threat even to the existence of life itself. For the sake of posterity, it is the duty of each one of us to protect the earth’from getting polluted.

Chemical Changes Textbook Questions and Answers

Electrolytic water Equipment Factory Question 1.
Assess the chemical reactions given below and answer the questions.
1. Calcium carbonate + heat → Calcium oxide + Carbon dioxide
2. Calcium oxide + water → Calcium hydroxide + heat
a. Mention the reactants and products in each case.
b. Which among these is endothermic? Which one is exothermic?
Answer:
a.Reactants:
1. Calcium carbonate
2. Calcium oxide, water
Products
1. Calcium oxide, carbon dioxide
2. Calcium hydroxide
b.First reaction is endothermic and second is exothermic reaction.

Hsslive Guru 8th Class Chemistry Kerala Syllabus Question 2.
Some chemical reactions are given below. Identify the energy change involved and write down what type of chemical reaction takes place here.
a. Burning of a candle
b. Glowing of a fire fly
c. Plating a copper ring with gold
d. Reaction between potassium hydroxide and sulphuric acid
e. Burning of fuels
Answer:
a. Thermochemical reactions
b. Photochemical reaction
c. Electrochemical reaction
d. Thermochemical reactions
e. Thermochemical reactions

Kerala Syllabus 8th Standard Chemistry Notes Malayalam Medium Question 3.
A student tries to plate an iron nail with copper. Draw its arrangement by selecting the required materials from the list given below.
Silver nitrate, iron nail, copper sulphate, silver rod, copper rod, silver plate, iron sulphate, battery, wire, water, beaker.
Answer:

8th Standard Chemistry Textbook Answers Kerala Syllabus Question 4.
List out the instruments that use electrochemical cells. What are the merits and demerits of using such cells?
Answer:

Std 8 Chemistry Notes Kerala Syllabus  Question 5.
Classify the following into physical changes and chemical changes.
1. Melting of ice.
2. Heating magnesium in water.
3. Silver bromide kept exposed to sunlight.
4. Change happening to soda water on opening its bottle.
Answer:
1. physical change
2. chemical change
3. chemical change
4. physical change

8 Standard Chemistry Notes Kerala Syllabus Question 6.
Give an example each for exothermic and endothermic reactions.
Answer:
Exothermic reaction:
Magnesium + hydrochloric acid → magnesium chloride + hydrogen + heat
Endothermic reaction:
Potassium permanganate + heat → potassium manganate + manganese dioxide + oxygen

Hss Live Guru 8th Chemistry Kerala Syllabus Question 7.
Making a volcano
Heap up some ammonium dichromate powder on a tile. Deposit on it the chemical present on a match stick, and ignite. Write down the changes happening there.
Change in colour: …………………………..
Change in amount: …………………………..
Exchange of energy: …………………………..
Answer:
Change in colour – orange-red Change in quantity – decreases Energy exchange – exothermic

Hsslive Guru Chemistry Class 8 Kerala Syllabus Question 8.
Kindling fire by pouring oil. Heap up some potassium permanganate on a tile. Keep a piece of dry cotton wick on top of it. Pour one or two drops of glycerine on the wick. Observe the changes.
Answer:
potassium permanganate heap burns

Basic Science Class 8 Chapter 6 Kerala Syllabus Question 9.
Take a magnesium ribbon and clean it by scrubbing. Then burn it in air. Collect the product formed and dissolve it in water. Dip litmus papers and pH paper in this solution and observe. Find out the reason for the results of the observations.
Answer:
Red litmus changes to blue. This is because of the magnesium hydroxide produced when magnesium oxide dissolved in water is alkaline.

8th Standard Chemistry Notes Kerala Syllabus Question 10.
Take sodium chloride solution in a beaker. Add to it a few drops of phenolphthalein. With the help of two carbon rods, let electricity pass through the solution. Record your observations. What is your inference?
Answer:
Sodium chloride is decomposed into sodium and chlorine

Question 11.
Take some silver nitrate solution in a test tube and add some sodium chloride solution to it. What is the colour of the precipitate formed? Filter the precipitate using a filter paper, place it on a watch glass and keep it exposed to sunlight. What do you observe?
Try to write down the equation of your observation with the help of your teacher.
Identify the change of energy involved in the second chemical reaction and write down what type of chemical reaction it is.
Answer:
White precipitate. It will become black when it is opened in sunlight.
Energy change: photo chemical reaction

Chemical Changes Additional Questions and Answers

Question 1.
i. sodium + water → sodium hydroxide + hydrogen
ii. Magnesium + oxygen → magnesium oxide
Write the reactants and products of these reactions.
Answer:
i. Reactants: sodium, water
Products: sodium hydroxide, hydrogen
ii. Reactants: magnesium, oxygen
products: Magnesium oxide

Question 2.
What is the observation when two drops of phenolphthalein is added to the solution obtained after the reaction of sodium with water? Justify your answer.
Answer:
The solution becomes pink in colour. The product of the reaction is sodium hydroxide which is alkaline.

Question 3.
Tabulate the following changes into physical and chemical changes

• Water changes to water vapour
• burning wood
• rusting the iron
• explosion of crackers
• cutting the wood
• Magnesium burns in air
• Ice is melting

Answer:
Water changes to water vapour – Physical change
Burning wood – Chemical change
Rusting the iron – Chemical change
Explosion of crackers – Chemical change
Cutting the wood – Physical change
Magnesium burns in air – Chemical change
Ice is melting – Physical change

Basic Science for Class 6 Chapter 6 Question 4.
Tabulate the important energy change in the following reactions.

1. Magnesium burns in air
2. Heating potassium permanganate
3. Photosynthesis
4. Electroplating
5. Reaction between Sodium hydroxide and Hydrochloric acid
6. Glittering the fire fly
7. Reaction in electrochemical cells

Answer:

1. Liberates heat energy
2. Absorbs heat energy
3. Absorbs light energy
4. Absorbs electric energy
5. Liberates heat energy
6. Liberates light energy
7. Liberates electric energy

Iron Sulphate Question 5.
Examine the following substances and draw the figure which shows the arrangement of coating silver on an iron ring Gold wire, silver rod, iron ring, copper sulphate, solution of silver cyanide and gold cyanide battery, beaker
Answer:

Question 6.
Some medicines and chemicals are kept in dark bottles, why?
Answer:
To prevent the chemical change due to the absorption of light

Question 7.
What is elecroplating? How are the electrode and the electrolyte selected when a metallic object is to be plated with another special metal?
Answer:
To obtain a thin coating of a particular metal on another metallic object using electricity is known as electroplating.

The metal to be plated is taken as the positive electrode. The electrolyte is a solution of salt containing the metal to be plated. The negative electrode is the metallic object to be plated.

Question 8.
What is your observation when a glowing in inscent stick is brought to the mouth of test tube containing potassium permanganate which is heated? Give reason.
Answer:
The stick flares up. When potassium permanganate is heated, it decomposes to form potassium manganate, manganese dioxide and oxygen.

Question 9.
Give an example each for the reaction of liberation of heat and absorption of heat from daily life.
Answer:
Exothermic reaction: Burning of wood
Endothermic reaction: Marble is heated to quick lime

Question 10.
How electrical energy is produced by batteries?
Answer:
Tn a battery, electrical energy is produced by the chemical reaction between zinc and sulphuric acid or by zinc and carbon. Electrical energy is produced by chemical reactions. Here chemical energy is converted to electrical energy.

Question 11.
Photosynthesis is the reaction that responsible to sustain life on the earth. Write the equation of the reaction. What is the energy change in it?
Answer:
6H₂O + CO₂ → C₆H₁₂ O₆+ 6O₂
Light energy is absorbed in it.

Question 12.
Complete the figure given below

Answer:

Question 13.
Acid is added to water for its electrolysis. Why?
Answer:
Pure water is not an electric conductor. But if some acid, alkali or salt is added, lot of ions are formed in it and water will become an electric conductor.

Question 14.
When electricity is passed through copper sulphate solution using carbon electrodes kept in the solution, it decomposes.
A. By what name this process in known?
B. In which electrode is copper deposited dining the reaction?
C. Is there a colour change for the solution?
Answer:
a. Electrolysis
b. Negative electrode
c. The colour of the solution decreases.

You can Download Magnetism Questions and Answers, Summary, Activity, Notes, Kerala Syllabus 8th Standard Basic Science Solutions Chapter 11 help you to revise complete Syllabus and score more marks in your examinations.

Kerala State Syllabus 8th Standard Basic Science Solutions Chapter 11 Magnetism

Nowadays artificial magnets are used commonly. They are made by the alloy like alnico.

A magnet possesses directional property that a freely moving magnet always aligns itself in the north-south direction. If a magnet is arranged in such a way that it can move freely it will align itself in the north-south direction of the earth. It is because a magnet possesses directional property that a freely moving magnet always aligns itself in the north-south direction.

As far as magnets are concerned, like poles repel each other and unlike poles attract each other.

A compass is an instrument which is utilised the directional property of a magnet. Every magnet has two poles even if they are very small.

Magnetism Class 8 Notes Chapter 11 Kerala Syllabus Earth as a magnet

The earth acts like a large magnet. This was first discovered by the scientist William Gilbert. He found out that just as the earth has north and south geographically, it has the north pole and the south pole when considered as a magnet. The south pole of the earth’s magnet is near the geographic north pole and the north pole of the earth’s magnet is near the geographic south pole.

Magnetism Class 8 Notes Kerala Syllabus Chapter 11 Magnetic field

Magnetic lines of force are experienced in all dimensions around a magnet. The magnetic lines of force is experienced according to the strength of the magnet. Magnetic force is experienced in all dimensions around a magnet. This region around a magnet where the influence is felt is the magnetic field.

The flux density is the number of flux lines passing through unit area.

Kerala Syllabus 8th Standard Physics Notes Chapter 11 peculiarities of magnetic lines of force.

1. Magnetic lines of force do not intersect one another.
2. Magnetic lines of force bend sideways, when like poles of magnets come near each other.
3. When unlike poles of magnets come close to each other, the path of the magnetic lines of force is from the north pole of one magnet to the south pole of the other magnet.

The substances which are attracted by magnet is called magnetic substances.

Questions On Magnetism For Class 8 Kerala Syllabus Chapter 11 Magnetic Induction

Bring a pin in contact with the pole of a bar magnet. Is it not attracted? What if you bring another pin to the free end of the pin? It will also be attracted. If we bring another pin the second pin will attract the third. But when the first pin is removed from the magnet all pins will fall down. That is the pin acquired the magnetic force from the magnet.

The phenomenon of a magnetic substance acquiring magnetism due to the presence of a magnet is Magnetic Induction. The magnetic force acquired by the magnetic substance is the Induced Magnetism.

Whether under contact or without contact, the polarity of the magnet produced by induction will be like polarity at the further end and unlike polarity at the nearer end.

The ability of magnetic substances to get magnetised under the influence of a magnetic field is Susceptibility. Retentivity is the ability to retain the magnetism thus acquired. Soft iron has high susceptibility. But the ability to retain magnetism acquired (retentivity) is very low.

Permeability is the ability of substances to pass magnetic lines of force through them.

The ability of soft iron to permit magnetic lines of force pass through it is greater than that of air. That is, magnetic lines of force pass more easily through soft iron than through air.

Std 8 Physics Magnetism Notes Kerala Syllabus Chapter 11 Electromagnet

Electromagnets can be made by passing electric current through insulated copper wire wound on a soft iron piece. The strength of electromagnets made in this way depends on

• the number of turns of coiled conductor
• the strength of current
• the area of cross section of the soft iron placed inside the coil

All electromagnets are temporary magnets. If the current ceases to flow, the magnetism of the soft iron core is lost.

Magnetism Textbook Questions and Answers

Magnetism Chapter Class 8 Kerala Syllabus Chapter 11 Question 1.
In the figure, AB is a bar magnet. CD is a soft iron rod placed near the end B. Write down which poles develop at the ends C and

Answer:
C-north ,D-South

Class 8 Physics Notes Kerala Syllabus Chapter 11 Question 2.
Figures A and B show two iron nails each hanging from a bar magnet and a U shaped magnet.

a. Identify the correct picture in A and B.
b. Justify your answers.
Answer:
a. A – Fig III B – Fig II
b.In A two nails are hang from bar magnet. So the distant ends will be induced the same pole. So repulsion. But in U magnet at the distant opposite poles will be induced. So attraction.

Hsslive Guru 8th Class Physics Kerala Syllabus Chapter 11 Question 3.
You are given a soft iron piece, a steel piece of the same size, insulated copper wire and a battery.
a. Explain how a strong permanent magnet can be made.
b. Suggest a method to make a temporary magnet.
Answer:
a. Take a piece of steel and bind a insulated copper wire. Connect the ends of the wire to a cell
b. Wind a few turns of insulated copper wire on an iron nail. Connect the ends of the wire to a cell

Basic Science Class 8 Chapter 11 Kerala Syllabus  Question 4.
Can you build a compass and make it work by arranging a magnetic needle in such a way that it rotates freely inside an iron case? What is the reason?
Answer:
No. As the iron is a magnetic substance compass will not rotate freely.

Hss Live Guru 8th Physics Kerala Syllabus Chapter 11 Question 5.
In an exhibition, a plastic car with an iron piece fixed inside it is made to run on a wooden table by sliding a strong magnet below it. The experiment failed when a steel table was used instead. Explain the reason.
Answer:
Steel table has high permeability. It permit magnetic flux to pass through it. Therefore we cannot slide the car using magnet.

Magnetism Additional Questions and Answers

Class 8 Science Notes Kerala Syllabus Chapter 11 Question 1.
Name the following magnet.

Answer:
a. Bar magnet,
b. compass,
c. U magnet,
d. Ring magnet,
e. Magnetic plate

8th Class Biology Notes Pdf Malayalam Medium Chapter 11 Question 2.
Which instrument is used to identify the direction in ship journey in ancient time?
Answer:
Compass

8th Class Biology Notes Pdf Kerala Syllabus Chapter 11 Question 3.
A bar magnet is hanged by a thread. Where does the north pole of the magnet point?

Answer:
The north pole of the compass points towards north of the earth that is south pole of earth’s magnet be¬cause earth is a magnet.

Kerala Syllabus 8th Standard Physics Notes Pdf Chapter 11 Question 4.
Write the magnetic substances from the following.
Wooden block, iron nail, paper, nickel, gold, cobalt, aluminium
Answer:
Iron nail, nickel, cobalt

Kerala Syllabus 8th Standard Chemistry Notes Chapter 11 Question 5.
Write the right statement
Greater susceptibility (Soft iron/Steel)
Greater retentivity? (Soft iron/ Steel)
Answer:
a. Soft iron b. Steel

Magnetism Chapter for Class 6 Question 6.
Write three method to increase the strength of an electromagnet.
Answer:

• the number of turns of coiled con ductor
• the strength of current
• the area of cross section of the soft iron placed inside the coil.

Magnetism Textbook Question 7.
You are given a bar magnet. The poles are not marked on it. Suggest a method to identify the poles of the magnet.
Answer:
The magnet is suspended using a thread so that it can oscillate freely in a horizontal plane. When it comes to rest the end pointing south can be marked as south pole.

Magnetism Solutions Question 8.
A magnet is dipped in iron filing, the iron fillings are more attracted towards the poles of the magnet than towards other places. Why?
Answer:
The intensity at the poles is greater than that at other places.

Question 9.
North of geomagnet inclined against 110 with geoscientific north pole? Examine the statement.
Answer:
The statement is incorrect. North of geomagnet inclined against 110 with geoscienfic south pole. Magnet suspended on geomagnet alinged south – north direction is due to the attraction of unlike poles. North pole (N) of magnet attracted towards the south pole of geomagnet.

Question 10.
What are the difference in the magnetic properties of iron and steel?
Answer:
Tron becomes a more intense magnet on magnetic induction. But that magnetic power is temporary. When the permanent magnet is removed it losses its magnetic power. In the presence of a magnet, steel doesn’t acquire the magnetic power like that of a soft iron. But steel retains most of its magnetic power after removing the permanent magnet.

Question 11.
Write your inferences.
a. All magnets have same shape.
b. All magnets show N, S direction when suspended freely.
c. All magnets are man made.
d. All magnets show N, S direction when suspended freely.
Answer:
a. No, There are different types of magnets.
b. Yes, Because the north pole of magnet turns to geographical south of earth and south pole turns to geographical north of earth.
c. No, There are natural and man made magnets.
d. Yes. Earth acts like a large magnet. Hence the poles of the suspended magnet is opposite to the poles of the earth’s magnet.

Question 12.
When an iron nail is wounded with copper wire and connected to a battery, it doesn’t become a magnet, select the reasons from the following.
a. Battery has not enough charge.
b. The insulation at the ends of the wire is not removed.
c. The nail is wounded with non insulated copper wire.
d. The polarity of the battery is changing.
Answer:
a,b,c

Question 13.
An Iron nail is suspended at the
north pole of a bar magnet. Bring the north pole of another magnet near the free end of a nail. What is observed? What is its reason?
Answer:
The free end of an iron nail repel. Because the free end of an iron nail becomes north pole by magnetic induction.

Question 14.
Complete the figure

Answer:

Question 15.
The pole of a magnet attracts an iron nail which has no magnetic power. Describe the work-ing behind this.
Answer:
The magnet attracts the iron nail brought near the pole of a magnet really as the result of magnetic induction. If the magnetic material reaches near the magnetic field of the magnet, an unlike pole is induced at its near end. The pole of permanent magnet is attract the newly formed unlike poles. That is why the magnetic pole attracts a magnetic material near it.

Question 16.
What are the factors that the attractive force of two magnetic poles depend on?
Answer:
The attractive force between the magnetic poles increases with increase in the strength of the pole and decreases with increase in the distance between the poles.

Question 17.
What is meant by atomic mag-nets?
Answer:
Each atom of a magnetic substance is an independent magnet. They are called atomic magnets.

Question 18.
What is meant by line of force (line of flux)?
Answer:
The line of force is the path that the north pole of a free magnetic needle would take around the bar magnet.

Question 19.
Examine the figure and mark the poles

Answer:

You can Download Diversity for Sustenance Questions and Answers, Summary, Activity, Notes, Kerala Syllabus 8th Standard Basic Science Solutions Chapter 13 help you to revise complete Syllabus and score more marks in your examinations.

Kerala State Syllabus 8th Standard Basic Science Solutions Chapter 13 Diversity for Sustenance

Diversity for Sustenance Textbook Questions and Answers

Diversity For Sustenance Kerala Syllabus 8th Chapter 13 Biosphere

Biosphere is the part of earth where life exists. Living world contains plants, animals, microorganisms, etc. Abiotic factors are also essential for the existence of living world. Sun is the ultimate source of energy in living world. Green plants convert light energy to chemical energy by photosynthesis.

Illustration (Text Book Page No:182)

Diversity For Sustenance Class 8 Kerala Syllabus Chapter 13 Question 1.
Discuss and complete the illustration given below suitably.

Diversity For Sustenance Pdf Kerala Syllabus 8th Chapter 13 Ecology

Ecology is the study of interrelationship of organisms among themselves and with their environment.

Basic Science Class 8 Chapter 13 Kerala Syllabus Chapter 13 Producers

Plants that perform photosynthesis are the producers.

Hss Live Guru Biology 8 Kerala Syllabus Chapter 13 Consumers

Organisms that directly or indirectly depend on green plants for energy are called consumers. Animals that directly depend plants are called primary consumers. Those dependent on primary consumers are the secondary consumers. The organisms depend on secondary consumers are called tertiary consumers.

Indicators (Text Book Page No: 183)

Hss Live Guru 8th Biology Kerala Syllabus Chapter 13 Question 1.
How do food chain and food web differ from each other?
Answer:
The chain of animals that eat and being eaten constitute food chain. But in nature different food chains are interrelated and this network is called food web.
Eg. Food Chain

8th Class Biology Notes Pdf Kerala Syllabus Chapter 13 Question 2.
Is a single organism involved in more than one food chain?
Answer:

• Same organism belongs to different food chains.
• Beneficial. No species increase or decrease beyond a level.

8th Class Physics Notes Kerala Syllabus Chapter 13 Question 3.
Is the possibility of an organism becoming food to more Is the possibility of an organism becoming food to more than one organism helpful to the existence of the food chain?
Why?
Answer:
If a particular species increase its number, the animals that forms its food get destroyed. It cause food scarcity and thus they themselves destroyed.

Diversity For Sustenance Notes Kerala Syllabus 8th Chapter 13 Question 4.
How does the variation in the number of a particular organism in the food chain affect the existence of other organisms?
Answer:
The number of an organisms decrease it adversely effects the existences of another group that depend them for their food. The increase and decrease in the number of organisms adversely affect the equilibrium of environments.

Hss Live Guru 8 Biology Kerala Syllabus Chapter 13 Trophic Level

Trophic level indicates the position of an organism in a food chain. Green plants belong to first trophic level. All food chains start from green plants. Herbivores are in II trophic level and Carnivores are included in III trophic level.

The Illustration (Text Book Page No: 184)

Basic Science For Class 8 Chapter 13 Question 5.
Did you read the note on trophic level?
Complete the illustration by including the organisms of the food web at various trophic levels
Answer:
Tertiary Consumers – Eagle, Mongoose
Secondary Consumers – Frog, Snake
Primary Consumers – Grasshopper, Rat
Producers – Grass, Paddy

Hsslive Guru Biology 8th Kerala Syllabus Chapter 13 Question 6.
Does the same organism occupy more than one trophic level?
Answer:
The same organism is included in different trophic levels as the complexity of food web increases.

Kerala Syllabus 8th Standard Chemistry Notes Chapter 13 Question 7.
Is there any possibility of a fifth trophic level?
Answer:
The number of trophic levels is an ecosystem is not constant. Even though in nature the food chains are not too long. This is to reduce the loss of energy during transmission.

Kerala Syllabus 8th Standard Physics Notes Chapter 13 Question 8.
How does the elimination of organisms from the higher trophic levels affect the ecosystem?
Answer:
The loss of organisms in higher levels cause tremendous increase in the number of organisms in the lower levels. It disrupt the equilibrium of environment.

Interactions in the Ecosystem

Many relations exist in nature. It maintains the equilibrium and stability of the ecosystem.
Food relations between organisms are good examples for these interactions.
Predation: One is benefitted. Other is harmed,
eg. Tiger and Deer.
Parasitism: One is benefitted. Other is harmed,
eg: Mango tree and Loranthus.
Competition: Both are harmed first. Later the winner is benefitted.
eg: Paddy and Weeds.
Mutualism: Both are benefitted
eg: Sea anemone and Hermit crab.
Commensalism: One is benefitted and the other is neither benefitted nor harmed.
eg : Mango tree and Vanda

Biodiversity

Biodiversity is the sum total of all the diverse species of organisms and their ecosystems (habitats)
Biodiversity has 3 different levels such as ecosystem diversity species diversity and genetic diversity.
Walter G. Rosen is the scientist who used the term ‘biodiversity’ for the first time.

Indicators (Text Book Page No: 186)

Hsslive Guru 8th Class Kerala Syllabus Chapter 13 Question 9.
Are all ecosystems alike in biodiversity?
Answer:
No.

Question 10.
Are all organisms seen in an ecosystem also seen in another ecosystem?
Answer:
Organisms adapted to the conditions of particular ecosystems. The physical and chemical structure of each ecosystem is different. So organisms seen in one ecosystem may not be present in another ecosystem.

Question 11.
What is the need for protecting natural ecosystems?
Answer:
Natural ecosystem are to be conserved for the existence and conservation of organisms. Ecosystems are the treasure houses of biodiversity. They provide innumerable services. Essential services, Ecological services, supporting services, and cultural services.

Indicators (Text Book Page No: 188)

Question 12.
Large scale destruction of ecosystems
Answer:
Birds are primary the victims of changes occurring in the ecosystem

Question 13.
Overexploitation of the natural resources
Answer:
The unwise interference of human beings destroys our ecosystem with rich biodiversity. If adversely affects the bird diversity in our locality. Many species of birds disappeared due to habitat loss. The pesticides like DDT, endosulfan used in agricultural field kills or drives away the birds that come
in search of food.

Conservation of Biodiversity

Conservation of organisms within their natural habitat is termed as in-situ conversation.
eg: Wildlife sanctuaries, National Parks, Community Reserves, etc.
Conservation of organisms outside their natural habitats is termed ex-situ conservation.
eg : Zoological garden, botanical garden, gene bank

Indicators (Text Book Page No: 183)

Question 14.
What is the scope of ex-situ conservation?
Answer:
It is possible to conserve the endangered animals by keeping them in specialized environment and by providing suitable conditions for reproduction. Rare species of plants can be conserved. Seeds, gametes, etc. can be collected and make we when necessary.

Question 15.
What is the significance of gene banks?
Answer:
Gene banks are research centers. Here special arrangements are these to collect seeds, gametes, etc. and to preserve them for long periods. Animals can be recreated when necessary.

Let US assess (Text Book Page No: 195) 

Question 16.
Phytoplankton – zooplankton – fish – seal – shark
a) In which trophic level is the secondary consumer of this food chain included?
b) Rewrite the food chain in such a way that the organism in the third trophic level figures in the second trophic level.
Answer:
a. In 3^rd trophic level.
b. algae → fish → duck

Question 17.
Find the odd one out from the following. Justify your answer.
a) Quagga, Malabar civet cat, Nilgiri Tahr, Lion-tailed macaque.
b) Eravikulam, Mathikettan shola, Periyar, Silent Valley
Answer:
a. Quaaga, Extinct
b. Periyar – Wildlife Sanctuary Others are national parks.

Question 18.
Examine the statements given below and rewrite if there are errors.
a) Extinct species are included in the Red Data Book.
b) WWF is an organisation working with the objective of protection of biodiversity.
c) Gene banks are included in in-situ conservation.
Answer:
In red data book endangered organisms are included
b. Right / True
c. Seed bank, sperm bank etc. are ex-situ conservation methods.

Diversity for Sustenance Additional Questions & Answers

Question 19.
Classify the following as producers and consumers.
Lizard, Planktons, Paddy, Calotes, Carrot, Grasshopper, Tortoise, Algae, Snake
Answer:

Question 20.
Find out suitable example for the animal relations mentioned.
i. Parasitism
ii. Mutualism
iii. Commensalism
Crops × Weeds
Mango tree × Vanda
Mango tree × Loranthus
Fish × Heron
Hermit crab × sea anemone
Answer:
i. Mango tree and Loranthus
ii. Hermit Crab – Sea anemone
iii. Mango tree and Vanda.

Question 21.
Complete the illustration Suitably

Answer:
a. Environmental / Ecological services
b. Cultural services
c. Food, Medicine
d. Nutrient Cycle, Pollination

Question 22.
Which are the different types of conservation of biodiversity?
Answer:
These are mainly two types.

1. In-situ conservation in which organisms are conserved within their natural environment
2. Ex-situ conservation in which animals are protected out their natural environment.

Question 23.
Classify the following into Ex-situ and In-situ.
(Zoological Gardens, Sacred Groves, Gene banks, Biosphere Reserves, Botanical Gardens, National parks)
Answer:

Question 24.
Expand the following terms.
Answer:
JNTBGRI – Jawaharlal Nehru Tropical Botanic Garden and Research Institute.
MBG – Malabar Botanical Garden RGCB – Rajiv Gandhi Centre for Biotechnology.

Question 25.
Why do all the food chains start from green plants?
Answer:
The basis of all food chains is the plants. They are the producers. These are eaten by the herbivores which in turn are eaten by the carnivores.

Question 26.
The members at the successively higher levels are lesser in number and larger in size in a food chain. What about their body weight? What would be the reason for that?
Answer:
In the successively higher levels in the food chain the number of consumers decreases and the size of their body increases. The number of producers will be very large. The number of animals which feed on them is less in number. But their body size increases.

Question 27.
Hay → Horse
Paddy → Fowl → Fox
Phytoplankton → Tadpole → Fish → Man
Grass → GrasshopperFrog → Snakes Vulture
Examine the food chain given above and classify them as primary consumers, secondary and tertiary consumers.
Answer:
Producers: Hay, Paddy, Phytoplankton, Grass
Primary consumer: Horse, Fowl, Tadpole, Grasshopper
Secondary consumers: Fox, Fish, Frog, Snake
Tertiary consumers: Vulture, Man

Question 28.
What will happen if the number of herbivores increases?
Answer:
If the number of herbivores increase they will eat away all the grass and shrubs and they will have to face shortage of food. The destruction of grass and shrubs will cause soil erosion and the top fertile soil will be washed away.

Question 29.
Animals which are facing extinction.
Answer:

• Wild goat
• Musk deer
• Indian wild Ass
• Lion-tailed Monkey
• Lion
• Rhinoceros
• The large Indian Bustard
• Tiger
• Kashmir deer
• Himalayan Tig
• Silver owl
• Panda

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Kerala State Syllabus 8th Standard Basic Science Solutions Chapter 12 Why Classification?

Why Classification? Textbook Questions and Answers

Classification

Classification is the grouping of organisms on the basis of similarities and differences. Classification using suitable criteria makes the study of organisms more easy. Many criteria are used in classification.
Eg: size, beauty, speed, type of teeth, claws, etc.

Taxonomic Keys

Scientific indicators used to recognize and classify plants and animals are called Taxonomic keys. Dichotomous keys is the most popular among these. Each indicator contains 2 options for selection. By selecting the characteristic feature of the organism to be identified it can be recognized and classified.

Indicators (Text Book Page No: 170)

Why Classification Class 8 Kerala Syllabus Chapter 12 Question 1.
Peculiarity of dichotomous keys
Answer:
Dichotomous key is the most popular among these. Each indicator contains 2 options for selection. By selecting the characteristic feature of the organism to be identified it can be recognized and classified.

Why Classification Kerala Syllabus Chapter 12 Taxonomy

Taxonomy is the branch of science that deals with the identification and classification of organisms according to similarities and differences. Organisms are given scientific names. Carl Linnaeus laid foundation stone for classification. In all organism that including human beings are placed in different levels of classification. It was scientist named carl Linnaeus who fixed taxonomic hierarchy and provided a scientific base for classification. Hence he is known as the father of taxonomy.

Scientists and their Contribution to Taxonomy

Aristotle:

Father of Biology Classified animals as red-blooded and non-red blooded

Theophrastus:

Father of Botany Grouped Plants as animals, biennials, and perennials

Charaka:

Father of Ayurveda Author of ‘Charaka Samhita’

John Ray:

– Used the term ‘Species’ for the first time
– Recorded more than 18000 plants in his book ‘Historia Generalis Plantarum’

Carls Linnaeus:

– Father of Modern Taxonomy.
– Suggested different levels of Classification
– Introduced Binomial Nomenclature

Why Classification Notes Kerala Syllabus Chapter 12 Indicators (Text Book Page No: 173)

Hss Live Guru Biology 8 Kerala Syllabus Chapter 12 Question 2.
Which are the organisms included in kingdom Animalia?
Answer:
Cockroach, Butterfly, Bird, Rabbit, Cat, Tiger, Lion, bear

Why Classification Class 8 Notes Kerala Syllabus Chapter 12 Question 3.
Which organisms are excluded at each consecutive level? Why?
Answer:

• Eliminated from Phylum Chordates — Butterfly, Cockroach
  Reason — Animals with vertebral columns alone are included in the phylum chordates.
• Eliminated from Class Mammalia
  — Bird (Pigeon) Reason — Animals that give birth to young ones alone included in this group.
• Eliminated from the order Carnivora — Rabbit
  Reason — Carnivores alone included in this order.
• Eliminated from the family Felidae — Bear
  Reason — It does not have retractile claws.
• Eliminated from the Genus Felis — Lion, tiger
  Reason — Animals having small body and without roaring sound are included.
• Eliminated from the Species domestic — Wild Cat
  Reason — It has the basic features of cat

Basic Science Class 8 Chapter 12 Solution Kerala Syllabus Chapter 12 Question 4.
At what levels of this illustration can humans be included?
Answer:
Man can be included in Class Mam-malia and Phylum Chordata.

Binomial Nomenclature

Binomial nomenclature is the scientific naming of organisms. Scientific name consists of two words. First word indicates genus and second word indicates species. Scientific name of man – Homo sapiens. Earlier two-kingdom classification was in practice. Accordingly, the organisms were broadly classified into planate and anemia. Later Rober. H. Whittaker classified organisms into 5 Kingdoms.
Eg : Monera, Protista, Fungi, Plantae, Animalia.
Another Scientist Carl Vaus added ‘domain’ above kingdom and expanded it into 6 kingdom classification.

Indicators (Text Book Page No: 176)

Class 8 Basic Science Chapter 12 Kerala Syllabus Chapter 12 Question 5.
Limitations of two-kingdom classification.
Answer:
Bacteria, Fungus, etc were not inclu­ded in two kingdom classification.

Hss Live Guru 8th Physics Kerala Syllabus Chapter 12 Question 6.
Possibilities of five kingdom classification.
Answer:
In five kingdom classification bacteri­a, amoeba, fungus, plants, and animals were included in separate kingdoms according to their characteristics.

8th Std Physics Notes Kerala Syllabus Chapter 12 Question 7.
Circumstances that led to the formulation of six kingdom classification.
Answer:
In ancient times knowledge regarding the characteristics of micro organ­isms was limited. It was found out that the cell structu­re and physiology of archaebacteria belongs to kingdom monera are quite different from other bacteria. Hence kingdom monera was divided into two kingdoms – Archae and Bacteria. Be­sides another level namely ‘domain’ was added above kingdom. Thus 6 king­dom classification came into existence

8th Standard Biology Kerala Syllabus Chapter 12 Question 4.
Completing the table (Text Book Page No: 177)

Answer:

Indicators (Text Book Page No: 178)

Basic Science Class 8 Chapter 12 Kerala Syllabus Question 8.
What are the peculiarities of virus?
Answer:
Viruses have no specific cell structure. Genetic material and a protein sheath alone are present. It is difficult to destroy them. They live only in living cells. They are dead or inactive outside the cell. It multiplies inside the host cell and destroys it.

Hss Live Guru 8 Biology Kerala Syllabus Chapter 12 Question 9.
Can virus be included in any of the classification methods we have discussed earlier? Why?
Answer:
As viruses have no cellular structure, it is not possible to include in any of the classifications mentioned.

Let US assess (Text Book Page No: 179) 

Basic Science For Class 8 Chapter 12 Kerala Syllabus Question 10.
Identify the word pair relation and fill in the blanks
a. Five kingdom classification: Robert H.Whittaker
Six kingdom classification :
b. Charaka: Charaka Samhita
John Ray
Answer:
a. Carl Vaus
b. Historia Generalis Plantarum

Kerala Syllabus 8th Standard Biology Notes Chapter 12 Question 11.
Hints about some organisms are given below. Name the
kingdom to which these organisms belong:
a. Multicellular heterotrophic organisms with a nucleus and capacity for locomotion.
b. Multicellular, heterotrophic, non-motile organisms with a nucleus.
c. Unicellular organisms with a nucleus.
d. Multicellular, autotrophic, non-motile organisms with a nucleus.
Answer:
a. Animals
b. Fungi
c. Amoeba
d.Plants

Kerala Syllabus 8th Standard Chemistry Notes Chapter 12 Question 12.
Write from the table the name of the organism which has more resemblances with tiger. Give explanations for your answer.

Answer:
Lion having the scientific name Pantheraleo.
Lion and Tiger belongs to same Genus ‘Panthera’

Why Classification? Additional Questions and Answers

Basic Science Class 8 Ch 12 Kerala Syllabus  Question 13.
Identify the word pair relation and fill the blanks.
a. 2 Kingdom Classification: Carls Linnaeus:: 5 kingdom Classification: …………….
b.Mushrooms: Fungi:: Bacteria: ……………..
c. Aristotle – Father of Biology Carls Linnaeus – …………….
d. Golden shower: Cassia fistula::…………..: Corvus splendens
e. Charaka: Father of Ayurveda::……………: Father of Botany
Answer:
a. R H Whittaker
b. Monera
c. Father of Taxonomy
d. Crow
e. Theophrastus

Hss Live Guru 8th Biology Kerala Syllabus Chapter 12 Question 14.
2. Identify the odd one and write the characteristic features of others.
a. Lion, Tiger, Rabbit, Cat.
b. Genus, Order, Carl Linnaeus, Phylum.
Answer:
a. Rabbit – Others including order Carnivora
b. Carl Linnaeus – He is the Father of Modern Taxonomy. Others are different levels of classification.

Question 15.
Which organism is most suit¬able for the following indicators (amoeba, bacteria, virus, Fungus)
1. Lives only in living cell
2. Pathogen
3. Only genetic material and a protein covering.
Answer:
Virus

Question 16.
Find out the scientists suitable to the statements given.
i. Author of Charaka Samhitha
ii. Author of Historia Generalis Plantarum
iii. Father of Modern Taxonomy
iv.Father of Biology
Answer:
i. Charaka
ii. John ray
iii. Carl Linnaeus
iv. Aristotle

Question 5.
Complete the table

Answer:

• Elephas Maximus / Elephas Indicus
• Pavo Cristatus
• Canis Familiaris
• Hibiscus Rosasinensis
• Azadiracuta Indica
• Oryza sativa

Question 17.
What are limitations in the system of classification of Carl Linnaeus?
Answer:
Some lower organisms share the characters of both animals and plants. So it is difficult to recognize them as plants or animals. Linnaeus considered only plants and animals for his classification. Microscopic organisms like bacteria, fungus, protozoa, etc were not included either in plant kingdom or in animal kingdom. Certain animals which were included in the classification of Linnaeus show characters of both the animal and plant kingdoms. Eg: Euglena protozoan shows locomotory movements like animals, but it contains chlorophyll like plants.

Question 18.
7. Hints about some organisms are given below. Name the kingdom to which these organisms belong.
a. Multicellular heterotrophic organisms with a nucleus and capacity for locomotion.
b. Multicellular heterotropic, non-motile organisms with a nucleus.
c. Unicellular organisms with a nucleus.
d. Multicellular, autotroph, non-motile organisms with a nucleus
Answer:
a. Animalia
b. Fungi
c. Protista
d. Plantae

Question 19.
Write the scientific name of following animals and plants. Coconut, paddy, wheat, crow, mango, grapes
Answer:
Coconut – Cocos nucifera
Paddy – Oryza sativa
Wheat – Triticum aestivum
Crow – Corvus splendens
Mango – Mangifera indica
Grapes – Vitis vinifera

Question 20.
What are two important characters of species?
Answer:
1. Species is a group of organisms that can freely interbreed to produce fertile offsprings.
2. A group of organisms that closely resemble each other in structure biochemical makeup and external characteristics but which are genetically different. In one species there may be subspecies.

Question 21.
The method of classification adopted by Whittaker is much better than the method adopted by Carl Linnaeus the father of the science of classification. What is your response to this statement?
Answer:
The classification of Linnaeus had only two kingdoms, plants, and animals. He did not consider bacteria, protozoa, fungus, etc. Certain characters of animals considered by Linnaeus for classification are found in both the kingdoms, eg. photosynthesis found in plants is seen in some animals like Euglena. Certain characters of animals can be seen in plants also, eg certain types of algae. But Whittaker adopted the method of having five kingdoms including protozoa and bacteria.

• Monera,
• Protista
• fungi
• Plantae
• animalia

Question 22.
Bacteria does not have a well defined Nucleus. Viruses are also like Bacteria. Why is it not possible to include viruses under Monera.
Answer:
Viruses exhibit living nature only when they enter the host cells. On other occasions, they do not exhibit living nature. But organisms in Monera are not like that.

Question 23.
How do the levels of classification of plants made by Carl Linnaeus differ from the levels of classification of Animals?
Answer:
Not much differences are there. In the place of ‘Order’ in animal classification, plant classification has series. And in the place of ‘Phylum’ in animal classification, plant classification has ‘Division’.

Question 24.
Find the level of classification and complete the given table.

Answer:
1. Kingdom
2.Phylum Chordata
3. Mammalia
4. Mammalia
5. Species

Question 25.
Cell is the smallest unit of life. But there are certain organisms that live without cell too. Analyze this statement.
Answer:
Life is not possible without a cell. Viruses do not have cells. As it is so, it does not have life when it outside a living cell. As it enters a living cell, it will show the features of life forms. It makes use of the components of the host cell and continues to live. Though it does not have a cell, it can continue its life only after entering a host cell and by making use of its components.

Question 26.
Observe the given statement, and write correct answer if you find false statements.
a. Aristotle is the Father of Biology.
b. John Ray is the Father of Botany.
c. Carl Linnaeus used the term ‘species’ for the first time.
d. Charaka proposed binomial nomenclature.
Answer:
a. True
b. False, Theophrastus
c. False, John Ray
d. False, Carl Linnaeus

Question 27.
What is the relationship between taxonomic keys and dichotomous key?
Answer:
Taxonomic keys are scientific indicators used to identify and classify plants and animals. Dichotomous keys is one of the popular taxonomic keys.

You can Download Equal Triangles Questions and Answers, Activity, Notes, Kerala Syllabus 8th Standard Maths Solutions Chapter 7 help you to revise complete Syllabus and score more marks in your examinations.

Kerala Syllabus 8th Standard Maths Solutions Chapter 7 Ratio

Area of Quadrilaterals Text Book Questions and Answers

Ratio Chapter Class 8 Kerala Syllabus Question 1.
In a regular polygon, the ratio of the inner and outer angle is 7 : 2. What is each angle? How many sides does the polygon
Solution:
Let the inner angle be 7x and the outer angle 2x .
Inner angle + outer angle = 180°
7x + 2x = 180°
9x = 180°
x = 180 ÷ 9 = 20°
Inner angle = 7x = 7 × 20 = 140°
Outer angle = 2x = 2 × 20 = 40°
Sum of the outer angles of a polygon of n sides is 360°. Since it is a regular polygon, the outer angles are equal,
n × 40 = 360°

Number of sides of the polygon = 9

Hsslive Maths Class 8 Kerala Syllabus Question 2.
The number of girls and boys in a class are in the ratio 7 : 5 and there are 8 more girls than boys. How many girls and boys are there in this class?
Solution:
Let the number of girls be 7x and the number of boys be 5x ,
Difference = 7x – 5x = 2x

Number of girls = 7x = 7 × 4 = 28
Number of boys = 5x = 5 × 4 = 20

Hsslive Class 8 Maths Kerala Syllabus Question 3.
Blue and yellow paints are mixed in the ratio 2 : 5 to make a new colour. 6 litres more of yellow 1 than blue is taken. How many litres of each is mixed?
Solution:
Let the measure of blue paint be 2x and yellow paint be 5x .
Their difference = 5x – 2x = 3x
3x = 6
x = 2
Quantity of blue paint = 2x = 2 × 2 = 4 litre
Quantity of yellow paint = 5x = 5 × 2 = 10 litre

Hsslive Guru 8th Class Maths Kerala Syllabus Question 4.
There are four right triangles, the ratio of perpendicular sides being 3 : 4 m each. One more fact about each is given below. Find the lengths of the sides of each triangle.
i. The difference in the lengths of the perpendicular sides is 24 metres.
ii. The hypotenuse is 24 metres.
iii. The perimeter is 24 metres.
iv. The area is 24 square metres.
Solution:
i. Let the perpendicular sides be 3x and 4x

The difference between the perpendicular sides be,
4x – 3x =x
x = 24
Sides are, 3x = 3 × 24 = 72 m
4x = 4 × 24 = 96 m
5x = 5 × 24 = 120 m

ii. Hypotenuse = 5x = 24

Perpendicular sides 3x = 3 × 4.8 = 14.4 m
4x = 4 × 4.8 = 19.2 m

iii. Perimeter = 3x + 4x + 5x = 12x
12x = 24
x = 2
Sides are, 3x = 3 × 2 = 6m
4x = 4 × 2 = 8 m
5x = 5 × 2 = 10 m

iv. Area = 1/2 × 3x × 4x = 6x ²
6x ² = 24
x ² = 4; x = 2
Sides are, 3x = 3 × 2 = 6m
4x = 4 × 2 = 8m
5x = 5 × 2 = 10 m

Textbook Page No 137

8th Std Maths Guide Kerala Syllabus  Question 5.
Acid and water are mix ed in the ratio 4 : 3 to make a liquid. On adding 10 more litres of water, the ratio changed to 3 : 1. How many litres of acid and water does the liquid contain now?
Solution:
Let the volume of acid be 4x and volume of water be 3x volume of acid on adding 10 more litres of acid = 4x + 10 litres
present ratio = 3 : 1
4x + 10 : 3x = 3 : 1
3 × 3x = 1 × (4x + 10)
9x = 4x + 10
9x – 4x = 10 ; 5x = 10
x = 2
Volume of acid in the original mix ture = 4x = 4 × 2 = 8 litres
Volume of water in the original mix ture = 3x = 3 × 2 = 6 litres
Volume of acid in the present mix ture = 8 + 10 = 18 litres
Volume of water in the present mix ture = 6 litres

Hss Live Maths Class 8 Kerala Syllabus Question 6.
Two angles are in the ratio 1 : 2. On increasing the smaller angle by 6° and decreasing the larger angle by 6°, the ratio changed to 2 : 3. What were the original angle?
Solution:
Let x be the smaller angle and 2x be the larger angle,
x + 6 : 2x – 6 = 2 : 3
2(2x – 6) = 3 (x +6)
4x – 12 = 3x + 18
4x – 3x = 18 + 12 = 30; x = 30
Original smaller angle = x ° = 30°
Original larger angle =2x ° = 6o°

Hss Live Guru 8th Maths Kerala Syllabus Question 7.
The sides of a rectangle are in the ratio 4 : 5.
i. By what fraction should the shorter side be increased to make it a square?
ii. By what fraction should the longer side be decreased to make it a square?
Solution:
Let 4x be the smaller side and 5x be the larger side,
i. Let y part of a shorter side be added breadth after adding = 4x + 4xy = 4x (1 + y)
Ratio of breadth and length of a square = 1 : 1
so present ratio
4 × (1 + y) : 5x = 1 : 1
1 × 4x (1 + y) = 5x × 1
4(1 + y) = 5

On adding \(\frac{1}{4}\) part of the original breadth, it can be made into square,

ii. Let y part of the longer side be substracted length after subtracting = 5x – 5xy
= 5x (1 – y)
As the present ratio is 1 : 1
5x (1 – y) : 4x = 1 : 1
1 × 5x (1 – y) = 1 × 4x
5 (1 – y) = 4

On subtracting \(\frac{1}{5}\) part of the original length, it can be made into square.

Hss Live Guru 8 Maths Kerala Syllabus Question 8.
Two quantities are in the ratio 3 : 5
i. If the smaller alone is made four times the original, What would be the ratio?
ii. If the smaller is doubled and the larger is halved, What would be the ratio?
Solution:
i. Let 3x be the smaller side and 5x be the larger side,
4 times the smaller = 4 × 3x = 12x
present ratio = 12x : 5x = 12 : 5

ii. Double the smaller = 2 × 3x = 6x

Kerala Syllabus 8th Standard Maths Notes Question 9.
i. The capacities of two bottles are in the ratio 3 : 4. The smaller bottle was filled twice and the larger bottle was filled and emptied into a vessel. Twice the smaller and half the larger was emptied into another. What is the ratio of the quantities of water in the two vessels?

ii. In the problem, what is the capacities of the bottles are in the ratio 4 : 7?
Solution:
i. Let the capacity of the smaller bottle = 3x
the capacity of the larger bottle = 4x
Volume of water when the smaller bottle is filled twice = 2 × 3x = 6x
Volume of water when the larger bottle is filled once = 4x
Total volume now = 6x + 4x = 10x
Volume of the water when the smaller bottle is filled twice = 6x
Volume of water when larger bottle is filled half = \(\frac{4 x }{2}\) = 2x
Total volume now = 6x + 2x = 8x
Ratio of the quantities of water = 10x : 8x , = 10 : 8 = 5 : 4

ii. Ratio of capacities of the bottle = 4 : 7
Let the capacity of the smaller bottle = 4x
the capacity of the larger bottle = 7x
Volume of water when the smaller bottle is filled twice = 2 × 4x = 8x
Volume of water when the larger bottle is filled once = 7x
Total volume now = 8x + 7x = 15x
Volume of the water when the smaller bottle is filled twice = 8x
Volume of water when larger bottle is filled half = \(\frac{7 x }{2}\)

= 30 : 23 (multiplied by 2)

8th Std Maths Notes Kerala Syllabus Question 10.
The breadth and length of two rectangles are in the ratio 2 : 3. In another rectangle, whose breadth is 1 cm less and length is 3 cm less than those of the first, this ratio is 3 : 4. Calculate the breadth and length of both rectangles.
Solution:
Ratio between the breadth and length of the first rectangle = 2 : 3
Breadth of the first rectangle = 2x
Length of the first rectangle = 3x
Breadth of the second rectangle = 2x – 1
Length of the second rectangle = 3x – 3
Ratio between the breadth and length = 3 : 4
so, (2x – 1) : (3x – 3) = 3 : 4
3 (3x – 3) = 4 (2x – 1)
9x – 9 = 8x – 4
9x – 8x = -4 + 9
x = 5
Breadth of the first rectangle = 2x = 2 × 5 = 10cm
Length of the first rectangle = 3x = 3 × 5 = 15 cm
Breadth of the second rectangle = 2x – 1 = 10 – 1 = 9 cm
Length of the second rectangle = 3x – 3 = 15 – 3 = 12 cm

Textbook Page No 141

Hsslive Guru Class 8 Maths Kerala Syllabus Question 11.
Johny invested 50000 rupees, Jaleel 40000 rupees and Jayan 20000 rupees to start a business together. They got 3300 rupees as profit in a month, which they divided in the ratio of their investments. How much did each get ?
Solution:
Ratio of the investment = 50000 : 40000: 20000 = 5 : 4 : 2
Profit of one month = 3300 rupees

Kerala Syllabus 8th Standard Notes Maths Question 12.
The capacities of three water tanks are in the ratio 2 : 3 : 5. The smallest of them can hold 2500 litres. How many litres can the other two hold ?
Solution:
Ratio of the capacities = 2 : 3 : 5
Let the capacities be 2x , 3x , 5x
Quantity of water in smaller tank = 2x = 2500
x = 1250 litres
Capacity of second tank = 3x = 3 × 1250 = 3750 litres
Capacity of third tank = 5x = 5 × 1250 = 6250 litres

Maths Guide For Class 8 Kerala Syllabus Question 13.
The angles of a triangle are in the ratio 1 : 3 : 5. How much is each angle?
Solution:

Class 8 Maths Notes Kerala Syllabus Question 14.
The outer angles of triangle are in the ratio 5 : 6: 7. What are the angles ?
Solution:
Sum of outer angle = 360°
Let the angles be 5x , 6x , 7x
5x + 6x + 7x = 360°
18x = 360°
x = 20°
Angles are = 5x =5 x 20 = 100°
6x = 6 × 20 = 1200
7x = 7 × 20 = 140°

8th Standard Maths Notes Kerala SyllabusQuestion 15.
The sides of a triangle are in the ratio 2 : 3 : 4. The longest side is 20 cm more than the shortest side. Calculate the length of all three sides.
Solution:
Let sides be 2x , 3x , 4x then,
Since the longest side is 20 cm more than the shortest side,
4x = 2x + 20, 4x – 2x = 20
2x = 20
x = 10
First side = 2 × 10 = 20 cm
Second side = 3 × 10 = 30 cm
Third side = 4 × 10 = 40 cm

Class 8 Chapter 7 Maths Kerala Syllabus Question 16.
A box contains beads of three colors. Black beads and white beads are in the ratio 3 : 5. White and red beads are in the ratio 2 : 3. What is the ratio of all three colors ?
Solution:
Black beads : White beads: Red beads

Hsslive Guru 8 Maths Kerala Syllabus Question 17.
The length, breadth and height of a rectangle block are in the ratio 3 : 2 : 5 and its volume is 3750 cubic centimetres. Calculate the length, breadth and height.
Solution:
Let breadth be 3x , length be 2x and height be 5x , then
3x × 2x × 5x = 3750
30 × 3 = 37
x = 5
Breadth = 3x = 3 × 5 = 15 cm
Length = 2x = 2 × 5 = 10 cm
Height = 5x = 5 × 5 = 25 cm

Additional Questions And Answers

Hss Live Guru Maths 8th Kerala Syllabus Question 1.
Sides of a triangular plot are in the ratio 3 : 5 : 7. Perimeter of the plot is 150 meter. Find the length of the sides.
Solution:
Perimeter = 150 m

= 30 m, 50 m, 70 m

Question 2.
The denominator and numerator of fraction are in the ratio 3 : 1. If \(\frac{1}{2}\) part of the numerator is added to it, prove that the ratio becomes 2 : 1.
Solution:

Ratio between denominator and numerator, when \(\frac{1}{2}\) part of the numerator is added to it, then the ratio is 6 : 3 = 2 : 1

Question 3.
Arun, Varun and Hari bought two packet of sweets, 245 in all. The ratio of the number of sweets Arun took to the number of sweets Varun took is 3 : 4. The ratio of the number of sweets Varun and Hari took is 6 : 7
How many sweets did each take?
Solution:

Question 4.
In a goat farm, the ratio of the number of goats which give milk to the number of goats which don’t is 6 : 2. The number of goat which don’t give milk is 160. How many goats do give milk? And how many goats are there in all?
Solution:
Ratio of the number of goat which give milk to the number of goat which don’t = 6 : 2
We have to find how many times the number of goat which don’t give milk is the number of goats which give milk is \(\frac{6}{2}\) times
that the number of goats which don’t give milk.
Therefore the number of goats which give milk \(160 \times \frac{6}{2}=480\)
Total number of goats = 160 + 480 = 640

Question 5.
Length and breadth of a rectangle are in the ratio 5 : 3. How many parts of the length of this rectangle is to be deducted so as to get the ratio of the length and breadth of the new rectangle is 7 : 6?
Solution:
5 : 3 = 10 : 6
If \(\frac{3}{10}\) part of 10 is deducted from it, the ratio is 7 : 6
That is \(\frac{3}{10}\) part of the length is deducted from it, the ratio is 7 : 6

Question 6.
In a school, the ratio of the number of boys to the number of teachers 2 : 3; and the ratio of the number of teacher to the number of girls is 4 : 5. What is the ratio of the number boys to girls.
Solution:
boys : teacher : girls

Question 7.
The ratio between the number of boys and girls in a college is 8 : 5. If the number of girls is 800, find the total number of students.
Solution:
Let the number of boys = 8x
Let the number of girls = 5x
5x = 800
x = 800 ÷ 5 = 160
Number of boys = 8 × 160 = 1280
Total number of students = 800 + 1280 = 2080

Question 8.
The sides of a triangle are in the ratio 3 : 5 : 7. Its smallest side is 28 cm less than the largest side. Find the sides of the triangle.
Solution:
Ratio of the sides of the triangle = 3 : 5 : 7
3x = 7x – 28
7x – 28 = 3x
4x = 28
x = 28 ÷ 4
Smallest side = 3 × 7 = 21 cm
Second side = 5 × 7 = 35 cm
Largest side = 7 × 7 = 49 cm

Question 9.
To make a colour, red, blue and green paints mixed in the ratio 1 : 2 : 4. How much quantity red and green are needed for 10 bottle of blue paint?
Solution:
Let red paint be 1x bottle, blue paint
2x bottle and green paint 4x
2x = 10 x = 10 ÷ 2 = 5
Red paint needed = 1 × 5 = 5 bottles
Green paint needed = 4 × 5 = 20 bottles.

Question 10.
In a 50 litre mixture of milk and water, milk and water are in the ratio 3 : 2. How much more milk should be added to it to make the ratio as 3 : 1.
Solution:
Let the measure of milk = 3x litre and
that of water = 2x litre.
3x + 2x = 50, 5x = 50
x = 50 ÷ 5 = 10
Milk = 3 × 10 = 30 litres
Water = 2 × 10 = 20 litres
Let k more litre of milk is added to make the ratio 3 : 1
Then 30 + k : 20 = 3 : 1
30 + k = 60, k = 60 – 30 = 30
Measure of milk to be added = 30 litres

Question 11.
The length and breadth of a rectangle are in the ratio 8 : 5. The length is 9 centimetres more than the breadth. What are the length and breadth of the rectangle?
Solution:
Let the length of the rectangle = 8x and breadth = 5x
Their difference = 8x – 5x = 3x
This is given as 9 m, 8x – 5x = 9
3x = 9, x = 9 ÷ 3 = 3
∴ Length of the rectangle = 8 × 3 = 24 cm
Breadth of the rectangle = 5 × 3 = 15 cm

Question 12.
In a concrete, cement and sand are mixed in the ratio 4 : 3. Prove that double the quantity of cement should be added to it to make the ratio 4 : 1.
Solution:
cement : sand = 4 : 3
Let cement = 4x and sand = 3x .
Double of cement = 2 x 4x = 8x ,
Quantity of cement now = 4x + 8x = 12x
Quantity of sand = 3x
Their ratio now = 12x : 3x
= 12 : 3 (divided by x)
= 4 : 1 (divided by 3)
That is if double the quantity of cement is added, the ratio will become 4 : 1.

Question 13.
Ratio of the number of red beads and blackheads in a box is 6 : 5. If the number of red beads is 4 more than the number of black beads find the number of red beads and black beads in the box.
Solution:
Let the number of red beads = 6x
Number of black beads = 5x
6x – 5x = 1x ; = 6x – 5x = 4
This is given as 4. ∴ x = 4
Number of red beads = 6 × 4 = 24
Number of black beads = 5 × 4 = 20

Question 14.
The ratio of the number of boys to the number of girls in a school is 14 : 15. There are 27 more girls than boys. How many girls are there in this school? How many boys?
Solution:
Ratio of the number of boys to the number of girls = 14 : 15
Let girls be 15x & boys be 14x
Their difference = 15x – 14x
= x = 27
Number of girls = 15x = 15 × 27 = 405
Number of boys = 14x = 14 × 27 = 378

Question 15.
State that if the sides of a triangle are in the ratio 3 : 4 : 5, then it is a right angled triangle. If perimetre is 36 cm, then find the length of the sides?
Solution:
Sides are 3x , 4x and 5x

Square of two sides are equal to the square of the third side. Therefore, it is a right angled triangle.

Question 16.
Ratio of cement, sand and gravel in a concrete mixture are in the ratio 1 : 3 : 4. If 80 kilogram of mixture is to be prepare, what quantity of cement, sand and gravel are to be taken?
Solution:
Let quantity of cement = x,
Quantity of sand = 2x,
Quantity of gravel = 4x
x + 3x + 4x = 80
8x = 8o ⇒ x = 10
quantity of cement = x = 10 kg
quantity of sand = 3x = 3 × 10 = 30 kg
quantity of gravel = 4x = 4 × 10 = 40 kg

Question 17.
Did the sides of a triangle be in the ratio 3 : 5 : 8 ? Why ?
Solution:
Sides are 3x, 5x and 8x .
3x + 5x = 8x
here sum of two sides is equal to the third side.
But sum of two sides should be greater than the third side. So the given sides
3x, 5x and 8x are not the sides of a triangle.
Therefore the ratio 3 : 5 : 8 cannot be the sides of a triangle.

Question 18.
In ∆ ABC, AB : BC = 2 : 3, BC : CA = 4 : 5, then find AB : BC : CA.
Solution:

Question 19.
One side of triangle given below is 12 cm. P is the midpoint of BC. Find the ratio of areas between ∆ ABC and ∆ APC

Solution:

Question 20.
Area of a rectangle is 2400 sq.cm. If length and breadth are in the ratio 8 : 3, find length and breadth? If length and breadth are increased by 20 cm, then find the ratio between length and breadth
Solution:
Length = 8x
Breadth = 3x

length = 8 × 10 = 80,
Breadth = 3 × 10 = 30
When length and breadth are increased by 20, then length = 100;
Breadth = 50
length : breadth = 2 : 1