std. 9th - science and technology, english medium,...

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STD. IX Science

and Technology

Written as per the revised syllabus prescribed by the Maharashtra State Board of Secondary and Higher Secondary Education, Pune.

Printed at: Repro India Ltd., Mumbai

Sixth Edition: March 2016

10054_10512_JUP

P.O. No. 15191

Salient Features

• Exhaustive coverage of entire syllabus in “Question-answer format”.

• Covers answers to all Textual Questions, In-text Questions and Activities.

• Includes MCQs based on practicals and Questions based on diagrams /

flow-charts.

• Includes Higher Order Thinking Skills (HOTS). • Includes Solved and Practice Problems for better preparation.

• Neat and labelled diagrams.

• Includes Memory Maps at the end of each chapter to facilitate quick

revision.

Preface We bring to you “Std. IX: Science and Technology” a complete and thorough guide extensively drafted to boost the students’ confidence. This book has been written as per the latest syllabus and covers answers not only to the textual questions but also for the In-text questions and activities. All the important definitions, laws and formulae are also duly incorporated. In addition to this, solved and practice problems are included which not only aim at covering the topic but also make students ready to face the competition. The topic-wise classified “question and answer” format of this book helps students in easy comprehension. Numerical problems included at the end of respective topics help the student to understand the technique of solving them efficiently. Moreover, neat and labelled diagrams, wherever necessary, are given so as to provide sound understanding of the concept. It also includes MCQs based on Practicals (as per the latest paper pattern). Higher Order Thinking Skills (HOTS) questions have been added for the student to gain insight on the various levels of theory-based questions. Every chapter ends with a Memory Map to facilitate quick revision of the lesson learnt.

There is always room for improvement and hence we welcome all suggestions and regret any errors that may have occurred in the making of this book. Please write to us on : [email protected] A book affects eternity; one can never tell where its influence stops.

Best of luck to all the aspirants! From Publisher

No. Chapter Name Page No.

1 World of Matter 1

2 Understanding Matter 15

3 Inside the Atom 28

4 Counting Matter 39

5 Cell: The unit of Life 51

6 Life: Simple and Complex 71

7 Life Around You 98

8 Highway to Health 122

9 Quality Food, Quality Life 146

10 Moving Objects 169

11 The Laws of Motion 185

12 The Pull of the Earth 199

13 Why Bodies Float 212

14 Energy : The Driving Force 225

15 The Music of Sound 242

16 Bonding with Ecosystems 258

17 Solid Waste – Ecofriendly Management

271

Contents

Note: Textual Questions are represented by * mark. Intext Questions are represented by # mark. Section A : Chapter No. 3, 4, 10, 11, 12, 13, 14, 15, 16 Section B : Chapter No. 1, 2, 5, 6, 7, 8, 9, 17

1

Chapter 01: World of Matter

1.1 Properties of matter 1. ______ is a physical quantity which expresses

the amount of matter in a body. (A) Mass (B) Density (C) Volume (D) Temperature 2. The space inside a container that is occupied

by matter is its ______. (A) density (B) mass (C) volume (D) shape 3. ______ is the ratio of mass of a substance to

its volume. (A) Viscosity (B) Fluidity (C) Density (D) Elasticity 1.2 States of matter 4. Solids are usually ______ since their particles

are closely packed together. (A) soft (B) spongy (C) compressible (D) hard 5. A rubber band is a good example of solids

being ______. (A) elastic (B) rigid (C) hard (D) strong 6. Liquids do not have a definite ______. (A) volume (B) shape (C) density (D) mass 1.3 Change of state 7. The phase or state of matter can change when

the ______ of the substance changes. (A) temperature (B) mass (C) weight (D) amount 8. ______ is the fifth state of matter. (A) Liquid (B) Bose-Einstein condensate (C) Gas (D) Plasma 9. The ______ of a liquid is the temperature at

which the liquid gets converted into solid. (A) freezing point (B) melting point (C) boiling point (D) evaporation 10. Melting point of glucose is ______. (A) 100 oC (B) 218.4 oC (C) 150 oC (D) 110 oC

11. Water freezes at ______. (A) 101 oF (B) 32 oF (C) 212 oF (D) 202 oF 1.4 Evaporation, cooling by evaporation,

condensation 12. ______ is the process by which liquid gets

converted into gaseous form at any temperature below its boiling point.

(A) Melting (B) Evaporation (C) Freezing (D) Condensation 13. ______ is the formation of liquid drops from

vapour. (A) Evaporation (B) Condensation (C) Boiling (D) Melting 1.5 Sublimation 14. ______ is a process in which solids go directly

into gaseous state without going through the liquid state.

(A) Evaporation (B) Sublimation (C) Boiling (D) Melting 15. ______ is not a sublimatory substance. (A) Iodine (B) Camphor (C) Ammonium chloride (D) Solid ice 1.6 Absorption of heat 16. The outer side of the container of a solar

cooker is painted ______. (A) blue (B) black (C) white (D) red 17. Cricketers playing a test match wear ______

clothes. (A) blue (B) black (C) white (D) red 18. Traditionally umbrellas are ______ in colour. (A) yellow (B) blue (C) white (D) black

World of Matter01 Rewrite the following statements by selecting the correct option

2

Std. IX: Science and Technology

2

Experiment 1 : To measure the temperature of hot water as it cools and plot a time-temperature graph 1. When a sample of hot water is cooled slowly

to room temperature, the temperature of the sample _______.

(A) increases (B) decreases (C) remains constant (D) either increases or decreases 2. Under which condition will the hot water cool

faster? (A) When it is kept in open space. (B) When it is kept in a thermos flask. (C) When it is kept inside a refrigerator. (D) When it is kept near a burning stove. 3. Four students plot the time – temperature

graphs of hot water as it cools to room temperature. These graphs are given below:

The correct graph is plotted by _______. (A) Student A (B) Student B (C) Student C (D) Student D Experiment 2 : To separate the components of a given mixture of sand, common salt and ammonium chloride (or camphor) 1. The components of the mixture of common

salt and ammonium chloride can be separated by _______.

(A) sublimation (B) filtration (C) cooling (D) crystallization

2. When a mixture of sand, camphor and common salt is heated, camphor _______.

(A) condenses to a liquid (B) melts to a liquid (C) sublimates to a gas (D) remains as it is 3. On adding water to a mixture of sand and

common salt, _______. (A) both sand and common salt dissolve in

water (B) sand remains as it is but common salt

dissolves in water (C) common salt remains as it is but sand

dissolves in water (D) both sand and common salt remain

insoluble in water Experiment 3 : To determine the melting point of ice and the boiling point of water 1. The melting point of ice is _______. (A) 10 C (B) 0 C (C) 32 C (D) 100 C 2. The boiling point of water is ______. (A) 32 C (B) 80 C (C) 100 C (D) 150 C 3. The process by which a solid gets converted

into a liquid at a fixed temperature is called _______.

(A) melting (B) evaporation (C) boiling (D) condensation 4. The following phase changes will be observed

when ice is heated till it gets converted to steam:

A Heat Liquid Heat C The phases A and C are _______ respectively. (A) solid and liquid (B) solid and gas (C) gas and solid (D) liquid and gas 1.1 Properties of matter 1. The ______ of an object gives an indication of

the amount of matter that an object contains. 2. ______ is made up of very tiny particles. 3. Matter has ______ and ______. 1.2 States of matter *4. We usually find matter in ______, ______ and

______ forms. 5. The particles in a solid are bound to each other by a ______.

Fill in the Blanks

Practical Based Multiple Choice Questions

O Time

Tem

pera

ture

Student D

O Time

Tem

pera

ture

Student A

Tem

pera

ture

O Time Student C

O Time

Tem

pera

ture

Student B

3


Answer the following questions in one sentence each

6. Particles of a solid cannot move much. This is one of the ______ characteristics of solids.

7. Liquefied Petroleum Gas (LPG) cylinders are

used at home and ______ cylinders are used in vehicles.

8. ______ spread out to fill the container. 9. ______ can be easily compressed. 1.3 Change of state *10. On heating, solids get converted to ______

and ______ get converted to gases. 11. ______ describes a physical state of matter. 12. Our body temperature is measured in a unit

called the ______. 1.4 Evaporation, cooling by evaporation,

condensation 13. ______ is the process which creates clouds. 1.5 Sublimation *14. ______ and ______ are sublimatory

substances. 15. Out of sand and iodine, iodine is a ______

substance. 1.6 Absorption of heat 16. ______ enters the object and warms it. Answers 1. mass 2. Matter 3. volume, mass 4. solid, liquid, gaseous 5. force 6. physical 7. Compressed Natural Gas (CNG) 8. Gases 9. Gases 10. liquids, liquids 11. Phase 12. Fahrenheit 13. Condensation 14. Camphor, naphthalene balls 15. sublimatory 16. Heat 1.0 Introduction 1. What is matter? Ans: Anything that occupies space, has mass and

can be perceived through our senses is called matter.

1.1 Properties of matter 2. What is density? Ans: Density is the ratio of mass to volume.

Density (d) =Mass(m)

Volume(v)

3. What happens when kerosene and water are mixed?

Ans: When kerosene and water are mixed, kerosene forms the upper layer as it has less density than water.

*4. Why does ice float on water? Ans: Ice floats on water because density of ice is

less than density of water. 1.2 States of matter 5. What is a solid? Ans: A substance which has a definite shape and

volume is called a solid. Eg. Book, wall, rock, etc. 6. What is crystal lattice? Ans: The atoms in a crystal are arranged in a

regular repeating pattern called as crystal lattice.

7. What is rigidity? Ans: The property of the solids to maintain their

volume and shape when subjected to external forces is known as rigidity.

8. What is a liquid? Ans: A substance which does not have a definite

shape, but has a definite volume is called a liquid.

Eg. Water, Mercury, etc. 9. What is a gas? Ans: A substance which has neither a definite shape

nor a definite volume is called a gas. 1.3 Change of state 10. Give the different states of matter. Ans: There are five different states of matter: solid,

liquid, gas, plasma and Bose-Einstein condensate.

*11. How are gases liquefied? Ans: Gases are liquefied by lowering their

temperature below a particular temperature and by applying high pressure.

12. What is melting point of a solid? Ans: The temperature at which a solid gets

converted into a liquid is called the melting point of the solid.

13. What is melting? Ans: The process by which a solid gets converted

into the liquid state at a fixed temperature is called melting.

4


4

14. What is freezing point of a liquid? Ans: The temperature at which a liquid gets

converted into a solid is called the freezing point of the liquid.

15. Give the formula for conversion of

temperature in degree Fahrenheit to degree Celsius.

Ans: The formula for conversion of temperature in degree Fahrenheit to degree Celsius is:

(F 32) 5

9= C.

1.4 Evaporation, cooling by evaporation,

condensation 16. What is evaporation? Ans: Evaporation is the process by which a liquid

gets converted into the gaseous form at any temperature below its boiling point.

17. State the factors which affect rate of

evaporation of liquid. Ans: Surface area, temperature, humidity, wind

speed, etc. are the factors which affect the rate of evaporation of liquid.

18. What is condensation? Ans: Condensation is the formation of liquid drops

from vapour. 19. Which process creates clouds and is

essential for snow and rain formation? Ans: Condensation is the process which creates

clouds and is essential for snow and rain formation.

1.5 Sublimation 20. What is sublimation? Ans: The process in which a solid gets directly

converted into the gaseous state without going through the liquid state is called sublimation.

1.1 Properties of matter 1. State the characteristics of matter. Ans: Characteristics of matter: i. Matter is made up of very tiny particles. These particles have space between

them. ii. The particles of matter attract each

other. iii. Matter occupies space. iv. Matter has volume and mass.

1.2 States of matter 2. State the characteristics of solids. Ans: Characteristics of solids: i. Solids have a definite shape and

volume. ii. Solids are almost incompressible, i.e.,

their volume and shape do not change even if an external force is applied.

iii. Most solids are rigid, while some are elastic.

iv. The particles in a solid are closely packed and the forces holding these particles together are quite strong.

*3. Why do solids have a definite shape? Ans: Solids have a definite shape because: i. The particles of solids are very close to

each other. ii. The forces holding these particles are

strong. 4. What is elasticity of solids? Ans: Elasticity of solids: When an external force is applied to a solid,

its shape changes and when this external force is removed, the solid regains its original shape.

This property of solids is known as elasticity. Eg. Rubber band, spring, etc. 5. State the characteristics of liquids. Ans: Characteristics of liquids: i. Liquids have a definite volume. ii. Liquids do not have a definite shape.

They take the shape of the container in which they are kept.

iii. Liquids cannot be compressed easily. iv. Liquids flow and have the property of

viscosity. 6. State the characteristics of gases. Ans: Characteristics of gases: i. Gases flow. ii. Gases spread everywhere in the

available space. iii. Gases do not have definite shape and

volume. iv. Gases can be easily compressed. #7. It is easier to walk through air than

through water. Why is it so? Ans: i. Air is in gaseous state and water is in

liquid state. ii. In air, the particles are so far apart that the

resistance offered by air to the motion of a body through it is negligible.

iii. In water, the particles are closer than in air and the resistance offered by them is more than that of air.

Hence, it is easier to walk through air than through water.

Answer the following questions

5


1.3 Change of state *8. What is the physical state of water at: i. 257 °C ii. 100 °C iii. 0 °C Ans: i. At 257 °C, water is in gaseous state. ii. At 100 C, water co-exists in liquid and

gaseous state. iii. At 0 C, water co-exists in the solid and

liquid state. 1.4 Evaporation, cooling by evaporation,

condensation 9. Why does a desert cooler cools better on a

hot dry day? Ans: i. On a hot dry day, the temperature is

higher. Thus, there is more dryness in the surrounding air (i.e., relative humidity of the air is low).

ii. At a high temperature, rate of evaporation is more. Thus, a desert cooler produces more cooling which results in large fall in the temperature of its surrounding air.

Hence, a desert cooler cools better on a hot dry day.

#10. Why do we wear cotton clothes in summer? Ans: i. The temperature of the surrounding

becomes very high in summer due to which we feel hot and sweat.

ii. Cotton clothes absorb sweat easily. iii. Heat is taken from the body for

evaporation of sweat. iv. Thus, due to evaporation of sweat, body

temperature remains constant. Hence, we wear cotton clothes in summer. #11. We find dewdrops, especially in the early

morning on the leaves. Why? Ans: i. A given volume of air can hold a certain

maximum amount of water vapour at a particular temperature.

ii. As the temperature falls, the capacity of air to hold water vapour becomes less.

iii. During cold nights, the temperature of air may fall to dew point or below the dew point.

iv. Thus, excess of water vapour in air condenses to form drops which falls on the leaves at night.

Hence, we find dewdrops, especially in the early morning on the leaves.

1.6 Absorption of heat #12. Why do we paint the outer side of the

container of a solar cooker with black paint?

Ans: i. In a solar cooker, the food is cooked due to the heat energy obtained from the sun.

ii. A black surface absorbs about 98% of the incident heat radiation that falls on it.

iii. Due to this, the temperature of the solar cooker increases and the food is cooked properly.

Hence, we paint the outer side of the container of a solar cooker with black paint.

#13. Why do cricketers playing test match wear

white clothes? Ans: i. Different colours absorb heat in

different proportions. ii. White clothes reflect most of the radiant

heat falling on them. iii. Therefore, cricketers do not feel much

warmth even though it is hot outside. Hence, cricketers playing test match wear

white clothes. #14. Traditionally umbrellas are black in colour.

Why are they better than coloured ones?

Ans: i. A black surface absorbs about 98% of the incident heat radiation that falls on it.

ii. So, the black coloured umbrella absorbs the heat radiations and does not allow heat radiations to pass through.

Hence, black umbrellas are better than coloured ones.

#15. When you go for trekking, which coloured

cap do you prefer to use? Ans: White colour reflects most of the heat

radiations that falls on it.

Hence, when going for trekking, it is preferable to use white coloured cap.

#16. In the state of Rajasthan the temperatures

are very high in summer. Which colour for the roof is preferable in such regions?

Ans: i. In Rajasthan, where the temperatures are very high in summer, white colour for the roof is preferable.

ii. Due to this, the heat is reflected and the temperature of the house remains low.

6


6

1.3 Change of state 1. Describe the change of phase or change of

state of matter when energy is supplied or taken away from a substance.

Ans: Change of phase:

i. The phase or state of matter can change when the temperature changes.

ii. When the temperature is increased, solid gets converted into liquid and liquid gets converted into gas.

iii. As the temperature rises, matter moves to a more active state.

iv. If energy is supplied (like increasing the

temperature or increasing the pressure) or if energy is taken away (like decreasing the temperature or decreasing the pressure), a physical change occurs.

*2. The smell of hot sizzling food reaches you

several meters away, but to get the smell from cold food, we have to go close. Why?

Ans: i. The gas molecules from the hot sizzling food mix with air easily as these molecules have a lot of energy. Hence, the smell of hot sizzling food spread around in all the directions and reaches several meters away.

ii. But the gas molecules from cold food cannot mix easily with air as these molecules have low energy due to its low temperature.

Hence, we have to go close to get the smell from cold food.


condensation 3. How does the condensation and evaporation

process keep the earth’s climate balanced? Ans: i. Condensation is the formation of liquid

drops from vapour. ii. It usually occurs when a parcel of rising

air expands and cools. iii. If it cools enough, some of the water

vapour molecules clump together at a faster rate.

iv. This process creates clouds which results in rain and snow, causing the earth’s climate to become cooler.

v. When cloud form, the heat removed from the earth’s surface through evaporation is released again in the atmosphere.

Thus, the earth’s climate remains balanced. 1.5 Sublimation #4. How would you separate the mixture of

sand and iodine crystals? Ans: i. In the mixture of sand and iodine

crystals, sand is not sublimatory while iodine is a sublimatory substance.

ii. By using sublimation method, we can separate the constituents of this mixture.

iii. Take this mixture in a china dish. iv. Put an inverted gas funnel over it. Place

a cotton plug in its stem. v. Heat the china dish. Iodine undergoes

sublimation and its vapours get condensed on the inner side of the funnel and cotton plug. Sand will remain in the china dish.


condensation 1. Evaporation Ans: i. Evaporation is the process by which a

liquid gets converted into the gaseous form at any temperature below its boiling point.

ii. All liquids can evaporate at room temperature and normal air pressure.

iii. In this process, atoms or molecules escape from the liquid and turn into vapour.

iv. There are always a few atoms or molecules with a lot of energy and some with very low energy.

Write short notes on

Answer in brief

+E+E

+E

Solid Liquid

Gas Plasma

Each addition of energy creates a change in state Inverted funnel

Iodine

China dish

Burner

Cotton plug

Mixture of sand and

iodine crystals

7


v. The atoms or molecules with lot of energy are able to build up enough energy to get converted into gaseous state.

vi. Once they reach that energy level, they leave the liquid state. As a result the liquid gets evaporated.

vii. The rate of evaporation depends upon the surface area, temperature, humidity, wind speed, etc.

1.2 States of matter 1. Solids are rigid. Ans: i. In solids, the particles are closely

packed together and the forces holding these particles are strong.

ii. As a result, solids are almost incompressible.

iii. Their volume is not changed by any outside force and their shape remains unchanged even if an external force is applied.

Hence, solids are rigid. 2. Gases are more compressible than liquids. Ans: i. In liquids, the distance between the

neighbouring particles is less than those in the gases.

ii. In gases, the particles have high energy. They spread out to fill the container and

there are no forces to stop them from going apart.

iii. Thus, in gases, the particles are very far apart and the forces of attraction between the particles are extremely weak as compared to liquids.

Hence, gases are more compressible than liquids.

3. Some liquids like honey flow slowly, while

other liquids such as kerosene flow rapidly. Ans: i. The differences in flow rate is due to the

property of viscosity. ii. More viscous a liquid, less is its rate of

flow. iii. Honey is more viscous than kerosene. Hence, some liquids like honey flow slowly,

while other liquids such as kerosene flow rapidly.

*4. A gas exerts pressure on the walls of a

closed container. Ans: i. In the gaseous state, the particles of a

gas move with a very high speed in all directions.

ii. Due to this, the particles collide with the walls of the closed container, where a pressure is created.

Hence, a gas exerts pressure on the walls of a closed container.

*5. In LPG cylinder, the gas filled is in the

liquefied state. Ans: i. Gases are highly compressible. They

can be compressed into very small volumes by applying high pressure.

ii. This process converts the gas into a liquid.

iii. As a result, a large volume of gas can be compressed into a liquid and stored in small LPG cylinders. Such cylinders can be easily transported from one place to another.

Hence, in LPG cylinder, the gas filled is in the liquefied state.


condensation 6. The tea in a saucer gets cooled faster than

in a cup. Ans: i. When we pour very hot tea in a saucer,

it cools quickly due to the process of evaporation.

ii. Evaporation takes place only at the surface of a liquid.

iii. The rate of evaporation is directly proportional to the surface area of a liquid.

iv. The exposed surface area of the tea in saucer is greater than the exposed surface area of the tea in a cup.

Hence, tea poured in a saucer gets cooled faster than in a cup.

1.5 Sublimation 7. Naphthalene balls disappear over a period of

time, without leaving behind any solid particles.

Ans: i. Naphthalene balls sublimate at room temperature.

ii. All its molecules go into vapour phase without changing into liquid.

iii. This process takes place when naphthalene balls absorb heat energy from the surrounding, which occurs slowly but continuously.

Hence, naphthalene balls disappear over a period of time, without leaving behind any solid particles.

Give scientific reasons

8


8

1. The state of matter having a definite shape and

volume. 2. The fourth state of matter. 3. A substance which is used as fuel in vehicles. 4. A substance which is used as ideal domestic

fuel in our home. Answers 1. Solid 2. Plasma 3. CNG (Compressed Natural Gas) 4. LPG (Liquefied Petroleum Gas) 1. Two objects can occupy the same space at the

same time. 2. When kerosene and water are mixed together,

water will form the upper layer. 3. The particles of a solid cannot move much. 4. Some liquids flow easily as compared to other

liquids. 5. More viscous liquids flow easily. 6. Liquids do not have a definite volume. 7. Gases cannot be compressed easily. 8. It is easier to walk through water than air. 9. Water freezes at 100 C. 10. The absorption of energy from the surrounding

reduces the temperature of the surrounding. 11. The rate of evaporation is not affected by

change in humidity. Answers 1. False: Two objects cannot occupy the same

space at the same time. 2. False: When kerosene and water are mixed

together, kerosene will form the upper layer. 3. True 4. True 5. False: Less viscous liquids flow easily. 6. False: Liquids have a definite volume. 7. False: Gases can be compressed easily. 8. False: It is easier to walk through air than water. 9. False: Water freezes at 0 C. 10. True 11. False: The rate of evaporation is affected by

change in humidity (i.e., it decreases with increase in humidity).

1. Water, Kerosene, Sugar, Milk 2. Stone, Common salt, Ice, Oil 3. Mercury, Hydrogen, Oxygen, Nitrogen 4. Camphor, Iodine, Water, Ammonium chloride Answers 1. Sugar: Others are liquids. 2. Oil: Others are solids. 3. Mercury: Others are gases. 4. Water: Others are sublimatory substances. 1. Solids 2. Rigid solids 3. Elastic solids 4. Liquids 5. Less viscous liquids 6. Highly viscous liquids 7. Gases 8. Sublimatory substances Answers 1. Blackboard, Ice 2. Stone, Iron 3. Rubber band, Spring 4. Milk, Oil 5. Water, Kerosene 6. Honey, Lubricants 7. Hydrogen, Oxygen 8. Iodine, Camphor 1. Wooden block: Solid :: Milk: ……. 2. Stone: Rigid :: Spring: ….. 3. Dust: Solid :: Carbon dioxide: …… 4. Solid: Incompressible :: Gas: ..….. 5. Water: Liquid :: Water vapour: …….. 6. Melting point of solid oxygen: 218.4 °C ::

Melting point of glucose: ..……. 7. Boiling point of water: .......... :: Freezing point

of water: 0 °C Answers 1. Liquid 2. Elastic 3. Gas 4. Compressible 5. Gas 6. 150 °C 7. 100 °C

State whether the following statements are true or false. If false, rewrite the correct statement.

T F

Find the odd man out

Give two examples of

Complete the analogy

Name the following

9


1.

Column I Column II

i. Solids a. High compressibility

ii. Liquids b. Incompressible

iii. Gases c. Low compressibility Ans: (i – b), (ii – c), (iii – a) 2.

Column I Column II

i. Solid converts into liquid a. Evaporation

ii. Gas converts into liquid b. Freezing

iii. Liquid converts into gas c. Melting

iv. Liquid converts into solid d. Condensation Ans: (i – c), (ii – d), (iii – a), (iv – b) *3.

State of matter

A

B

1. Gas a. Soil i. Milk

2. Solid b. Kerosene ii. Oxygen

3. Liquid c. Carbon

monoxide iii. Peas

Ans: (1 – c - ii), (2 – a - iii), (3 – b - i) 1. Solids and Liquids Ans:

Solids Liquids

i. Solids have definite shape.

Liquids do not have definite shape.

ii. Solids are almost incompressible.

Liquids are less compressible.

iii. Solids do not flow. Liquids flow.

Eg. Sugar, stone Water, milk 2. Liquids and Gases Ans:

Liquids Gases i. Liquids have definite

volume. Gases do not have definite volume.

ii. Liquids have very low compressibility.

Gases have high compressibility.

iii. Liquids flow upto certain extent.

Gases flow everywhere in the available space.

Eg. Water, kerosene Hydrogen, oxygen 3. Solids and Gases Ans:

Solids Gases i. Solids have definite

shape. Gases do not have definite shape.

ii. Solids have definite volume.

Gases do not have definite volume.

iii. Solids are almost incompressible.

Gases are highly compressible.

Eg. Table, iron Nitrogen, Oxygen 4. Evaporation and Boiling Ans:

Evaporation Boiling i. It takes place at all

temperatures below the boiling point of the liquid.

It takes place only at the boiling point of the liquid.

ii. It causes cooling. It does not cause cooling.

1. Sample structure of a solid Ans: 2. Effort needed to compress solid, liquid and

gas Ans:

Match the columns

Distinguish between the following pairs

More Less

Effort Needed to Compress

GasSolid Liquid

Draw neat & labelled diagrams of the following

Solid particles

10


10

3. Condensation due to the expansion of air Ans: 4. Condensation due to direct cooling of air Ans: 1. In the following figure, water changes into

ice: i. Which type of change is observed in

the process? ii. For this change of state, is energy

released or absorbed? Ans: i. Changing of water into ice is a physical

change. ii. In freezing (i.e., in conversion of water

to ice), energy is taken away from water. So, water releases energy to get converted into ice.

2. In the following figure, water changes to

hydrogen peroxide: i. Which type of change is observed in

the process? ii. Does the process involve change in

basic chemical structure of water? Ans: i. In the given process, chemical change is

observed. ii. Yes, the process involves change in

basic chemical structure of water as the water molecule (H2O) is converted to hydrogen peroxide molecule (H2O2).

3. Observe the following figure which shows the heating of ammonium chloride:

i. Name the process that occurs when ammonium chloride changes directly from solid state to gaseous state.

ii. Name other two substances which will show same behaviour as that of ammonium chloride when heated.

Ans: i. Sublimation ii. Camphor and iodine #1. Classify the following into solids, liquids

and gases: Air, bench, kerosene, bag, bottle, chalk, brass, water vapour, blackboard, dust, table, soil, chair, water, door, pen, milk, eraser, petrol, book, windowpanes, ice, diesel, carbon dioxide, cupboard, oxygen, mercury.

Ans:

Solids Liquids Gases

Bench, bag, bottle, chalk, brass, blackboard, dust, table, soil, chair, door, pen, eraser, book, windowpanes, ice, cupboard

Kerosene, water, milk, petrol, diesel, mercury

Air, water vapour, carbon dioxide, oxygen

#2. Suggest one scientific word for all of the

following changes: i. Solid wax converts into liquid wax. ii. Ice changes into water. iii. A plastic bowl kept near the flame,

changes its shape. iv. Frozen butter is kept outside the

refrigerator. Ans: Melting

Water Ice

H2O H2O2

Questions Based on Diagram

Miscellaneous

Liquid waterdroplets

Rising air parcel

Ice

Water

Inverted funnel

Ammonium chloride solidified

China dish

Burner

Cotton plug

Ammonium chloride

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Activity … II (Textbook page no. 1) Ans: i. No, we cannot count the number of

particles present in a piece of chalk. ii. The cotton cloth becomes wet due to

absorption of the liquid. iii. Yes, we can break the stream of water

with our fingers. iv. No, it is not possible to fill any more

liquid in the bottle as it is already filled up to the brim. There is air in the space which was earlier occupied by water.

Activity … III (Textbook page no. 2) Ans: i. The pebble will sink in water because

the density of the pebble is greater than the density of water. However, the plastic spoon will not sink in water because it has less density than water.

ii. Dry wood, ice, leaves, kerosene, oil, etc. are some substances which float on water.

Activity … IV (Textbook page no. 3 and 4) Ans: Observation: i. The liquids come down in the order of

decreasing speed as follows: kerosene > water > milk > honey ii. Among the four liquids, honey is the

most viscous and kerosene is the least viscous liquid.

iii. Kerosene, water and milk take the shape of the container faster.

iv. Honey forms layers and these layers take the shape of the container slowly.

Conclusion: Rate of flow of liquids depends on their viscosity. Activity ... V (Textbook page no. 4) Ans: i. Inflated balloons become heavier than

uninflated balloons because the air inside the inflated balloons also has some mass.

ii. a. Yes, we get the smell of incense stick in the other corner of the room.

b. When an incense stick is ignited, its material starts burning. The fragrance present in the incense stick is converted into gaseous state and spreads in all directions.

c. As gas molecules move faster than liquid or solid, they reach from one corner of a room to the other corner easily and so a person at the other corner gets its smell.

iii. Perfume is a volatile substance (easily escapes into air). Thus, the molecules of the perfume spread everywhere in the surrounding air. So, Sabiha can smell the perfume though she is sitting in a far off corner.

Activity … VI (Textbook page no. 5) Ans: i. Small droplets of the water are

observed on the inner surface of the lid because water vapours from the tea get condensed.

ii. In winter morning, the temperature of atmosphere is very low. The coconut oil freezes at this temperature and becomes solid. In the summer morning, the temperature of atmosphere is higher as compared to winter. Thus, oil does not freeze and remains in the liquid state.

Activity … VII (Textbook page no. 7) Ans: i. The wet handkerchief kept in the open

space would dry up faster. ii. The puddle will reduce in size due to

evaporation of water present in it. iii. We feel cold sensation at the site where

spirit is applied. iv. We pour very hot tea in a saucer to cool

it rapidly. By doing so, the exposed surface area increases and the rate of evaporation also increases which makes the tea cool faster.

v. a. The water kept in an earthen pot becomes cool due to the process of evaporation.

b. Large number of pores are present on the surface of earthen pot. Water comes out continuously from these pores into the outside environment.

c. As a result, evaporation takes place and the temperature of water in the pot decreases.

Hence, the water kept in an earthen pot (matka) becomes cool even in summer.

Activity … VIII (Textbook page no. 8) Ans: i. Camphor is a sublimatory substance. It

sublimates at room temperature and changes into gaseous state slowly. Due to this, camphor becomes smaller in size and finally disappears.

ii. Naphthalene balls sublimate at room temperature. They absorb heat energy from the surrounding and get converted into gaseous form. Naphthalene present in the gaseous form gets mixed with the air due to which the bad odour in the toilet reduces. So, naphthalene balls are kept in the toilets.

Activities

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Activity … IX (Textbook page no. 8) Ans: Ammonium chloride is a sublimatory

substance. When heated, solid ammonium chloride changes directly into gaseous state without changing into liquid state. Ammonium chloride, thus, gets deposited inside the inverted funnel and on the cotton plug.

1. Two vessels contain different types of

liquids A and B. If density of A is two times that of B and volumes of both the liquids taken in the vessels are the same, then which liquid has less mass?

Ans: Liquid B has less mass. 2. Why does the temperature of a substance

remain constant while changing from one state to another?

Ans: When a substance changes from one state to another, heat provided to the substance is utilised in increasing the distance between the molecules of the substance. However, the energy of the molecules (which is directly related to the temperature) does not increase.

Therefore, the temperature of a substance remains constant while changing from one state to another.

3. X and Y are two substances. They are given

same quantity of heat. X changes its state from solid to liquid. Y changes its state from solid to gas.

i. Can X change its state from liquid to gas when more heat is given?

ii. What kind of substance is Y? Ans: i. If more heat is given, then X can change

its state from liquid to gas. ii. Y is a sublimatory substance. 4. Complete the following chart:

Ans: 1. Solids

2. Liquids

3. Condense into liquids. Type I: Problems based on

Density(d) =Mass(m)

Volume(v)

#1. What is the density of a wooden block of

mass 4 grams and dimensions of

2 cm 3 cm 1 cm?

Ans: Given: m = 4 g, l = 2 cm,

b = 3 cm, h = 1 cm

To find: d = ?

Formula: i. v = l b h

ii. d = m

v

Solution:

From formula (i),

v = 2 cm 3 cm 1 cm

= 6 cm3

From formula (ii),

d = 3

4g

6cm = 0.67 g/cm3

The density of wooden block = 0.67 g/cm3 2. The mass of an iron block is 158 g and

density is 7.9 g/cm3. Calculate the volume of the block.

Ans: Given: m = 158 g, d = 7.9 g/cm3

To find: v = ?

Formula: density (d) = mass(m)

volume(v)

Solution:

From formula,

v = m

d

= 3

158g

7.9g/cm = 20 cm3

The volume of iron block = 20 cm3

3. The density of an object is 3.0 g/cm3 and its

volume is 8 cm3. Calculate the mass of the object.

Ans: Given: v = 8 cm3, d = 3.0 g/cm3

To find: m = ?

Solved Examples

HOTS

Melt into liquids. Sublimate into gases.

Matter

Gases

can be convertedinto

Evaporate into gases.Freeze into solids.

can be convertedinto

1 2

can be

3

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Formula: density (d) = mass(m)

volume(v)

Solution: From formula,

m = d v

= 3.0 g/cm3 8 cm3

= 24 g

Mass of the object = 24 g

Type II: Problems based on (F 32) 5

9= C

4. The temperature of an object is 20 °C.

Express this temperature in degree Fahrenheit.

Ans: Given: Temperature in degree Celsius (C) = 20 °C

To find: Temperature in degree Fahrenheit (F) = ?

Formula: (F 32) 5

9= C


(F 32) 5 = 9C 5F – 160 = 9C 5F = 9C +160

5F = 9 20 +160 = 180 +160 = 340

F = 340

5 = 68 F

Temperature in degree Fahrenheit = 68 F 5. The temperature of an object is 95 F.

Express this temperature in degree Celsius. Ans: Given: Temperature in degree Fahrenheit

(F) = 95 F To find: Temperature in degree Celsius (C) = ?

Formula: (F 32) 5

9 = C


C = (95 32) 5

9

= 63 5

9

= 7 5 = 35 °C

Temperature in degree Celsius = 35 C

Type I

1. The mass and volume of an object are 50 g and 25 cm3 respectively. Calculate the density of that object.

2. The volume and the density of an object is

18 cm3 and 4 g/cm3 respectively. Calculate the mass of that object.

3. Find the volume of an object having mass 27 g

and density 3 g/cm3. Type II 4. Express the following temperatures in degree

Fahrenheit.

i. 45 °C ii. 60 °C

iii. 15 °C iv. 70 °C 5. Express the following temperatures in degree

Celsius.

i. 104 °F ii. 122 °F

iii. 194 °F iv. 50 °F 1. 2 g/cm3

2. 72 g

3. 9 cm3

4. i. 113 °F ii. 140 °F

iii. 59 °F iv. 158 °F

5. i. 40 °C ii. 50 °C

iii. 90 °C iv. 10 °C Additional Theory Questions 1. Write the formula to calculate density of a

substance from its mass and volume.

Ans: Refer Answer the following questions in one sentence each Q.2. (Formula)

2. Explain why solids are incompressible.

Ans: Refer Give scientific reasons Q.1.(i) and (ii).

Practice Problems

Answers to Practice Problems

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Memory Map

Have definite shape and volume.

Almost incompressible.

Particles are compact and close together.

Different phases orstates of matter

Energy is supplied

Energy is taken away

Liquids

Energy is supplied

Energy is taken away

Solids

Have definite volume butdo not have definite shape.

Have very lowcompressibility.

Particles are little morespread out as compared tosolids.

Gases

Do not have definite shapeand volume.

Have high compressibility(i.e., can be easilycompressed).

Particles are very far apart.

Change in state Change in state Change in state

Solid Liquid Gas

Change in state Solids can be converted to: Liquids Melting Gases Sublimation

Change in state Liquids can be convertedto: Gases Evaporation Solids Freezing

Change in state Gases can be converted to: Liquids Condensation

Matter Made up of very tiny particles that

attract each other Occupies space Has volume and mass

std. 9th - science and technology, english medium,...

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