As we look at our surroundings, we see a large

variety of things with different shapes, sizes

and textures. Everything in this universe is

made up of material which scientists have

named “matter”. The air we breathe, the food

we eat, stones, clouds, stars, plants and

animals, even a small drop of water or a

particle of sand — every thing is matter. We

can also see as we look around that all the

things mentioned above occupy space and

have mass. In other words, they have both

mass* and volume**.

Since early times, human beings have

been trying to understand their surroundings.

Early Indian philosophers classified matter in

the form of five basic elements — the “Panch

Tatva” — air, earth, fire, sky and water.

According to them everything, living or non-

living, was made up of these five basic

elements. Ancient Greek philosophers had

arrived at a similar classification of matter.

Modern day scientists have evolved two

types of classification of matter based on their

physical pr

operties and chemical nature.

In this chapter we shall learn about

matter based on its physical properties.

Chemical aspects of matter will be taken up

in subsequent chapters.

1.1 Physical Nature of Matter

1.1.1 MATTER IS MADE UP OF PARTICLES

For a long time, two schools of thought prevailed

regarding the nature of matter. One school

believed matter to be continuous like a block

of wood, whereas, the other thought that matter

was made up of particles like sand. Let us

perform an activity to decide about the nature

of matter — is it continuous or particulate?

Activity ______________ 1.1

• Take a 100 mL beaker.

• Fill half the beaker with water and

mark the level of water.

• Dissolve some salt/ sugar with the help

of a glass rod.

• Observe any change in water level.

• What do you think has happened to

the salt?

• Where does it disappear?

• Does the level of water change?

In order to answer these questions we

need to use the idea that matter is made up

of particles. What was there in the spoon, salt

or sugar, has now spread throughout water.

This is illustrated in Fig. 1.1.

1.1.2 HOW SMALL ARE THESE PARTICLES

OF MATTER?

Activity ______________ 1.2

• Take 2–3 crystals of potassium

permanganate and dissolve them in

100 mL of water.

Fig. 1.1: When we dissolve salt in water, the particles

of salt get into the spaces between particles

of water.

* The SI unit of mass is kilogram (kg).

** The SI unit of volume is cubic metre (m

). The common unit of measuring volume is

litre (L) such that 1L = 1 dm

, 1L = 1000 mL, 1 mL = 1 cm

ATTERATTER

ATTER

ININ

O O

URUR

S S

URROUNDINGSURROUNDINGS

URROUNDINGS

hapter

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SCIENCE2

• Take out approximately 10 mL of this

solution and put it into 90 mL of clear

water.

• Take out 10 mL of this solution and

put it into another 90 mL of clear water.

• Keep diluting the solution like this 5 to

8 times.

• Is the water still coloured ?

1.2.2 PARTICLES OF MATTER ARE

CONTINUOUSLY MOVING

Activity ______________ 1.3

• Put an unlit incense stick in a corner

of your class. How close do you have to

go near it so as to get its smell?

• Now light the incense stick. What

happens? Do you get the smell sitting

at a distance?

• Record your observations.

Activity ______________ 1.4

• Take two glasses/beakers filled with

water.

• Put a drop of blue or red ink slowly

and carefully along the sides of the first

beaker and honey in the same way in

the second beaker.

• Leave them undisturbed in your house

or in a corner of the class.

• Record your observations.

• What do you observe immediately after

adding the ink drop?

• What do you observe immediately after

adding a drop of honey?

• How many hours or days does it take

for the colour of ink to spread evenly

throughout the water?

Activity ______________ 1.5

• Drop a crystal of copper sulphate or

potassium permanganate into a glass

of hot water and another containing

cold water. Do not stir the solution.

Allow the crystals to settle at the

bottom.

• What do you observe just above the

solid crystal in the glass?

• What happens as time passes?

• What does this suggest about the

particles of solid and liquid?

• Does the rate of mixing change with

temperature? Why and how?

From the above three activities (1.3, 1.4 and

1.5), we can conclude the following:

Fig. 1.2: Estimating how small are the particles of

matter. With every dilution, though the colour

becomes light, it is still visible.

This experiment shows that just a few

crystals of potassium permanganate can

colour a large volume of water (about

1000 L). So we conclude that there must be

millions of tiny particles in just one crystal

of potassium permanganate, which keep

on dividing themselves into smaller and

smaller particles.

The same activity can be done using 2 ml

of Dettol instead of potassium permanganate.

The smell can be detected even on

repeated dilution.

The particles of matter are very small –

they are small beyond our imagination!!!!

1.2 Characteristics of Particles of

Matter

1.2.1 PARTICLES OF MATTER HAVE SPACE

BETWEEN THEM

In activities 1.1 and 1.2 we saw that particles

of sugar, salt, Dettol, or potassium

permanganate got evenly distributed in water.

Similarly, when we make tea, coffee or

lemonade (nimbu paani ), particles of one type

of matter get into the spaces between particles

of the other. This shows that there is enough

space between particles of matter.

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MATTER IN OUR SURROUNDINGS 3

• If we consider each student as a

particle of matter, then in which group

the particles held each other with the

maximum force?

Activity ______________ 1.7

• Take an iron nail, a piece of chalk and

a rubber band.

• Try breaking them by hammering,

cutting or stretching.

• In which of the above three

substances do you think the particles

are held together with greater force?

Activity ______________ 1.8

• Take some water in a container, try

cutting the surface of water with your

fingers.

• Were you able to cut the surface of

water?

• What could be the reason behind the

surface of water remaining together?

The above three activities (1.6, 1.7 and 1.8)

suggest that particles of matter have force

acting between them. This force keeps the

particles together. The strength of this force of

attraction varies from one kind of matter to

another.

uestions

1. Which of the following are

matter?

Chair, air, love, smell, hate,

almonds, thought, cold, lemon

water, smell of perfume.

2. Give reasons for the following

observation:

The smell of hot sizzling food

reaches you several metres

away, but to get the smell from

cold food you have to go close.

3. A diver is able to cut through

water in a swimming pool. Which

property of matter does this

observation show?

4. What are the characteristics of

the particles of matter?

Particles of matter are continuously

moving, that is, they possess what we call

the kinetic energy. As the temperature rises,

particles move faster. So, we can say that with

increase in temperature the kinetic energy of

the particles also increases.

In the above three activities we observe

that particles of matter intermix on their own

with each other. They do so by getting into

the spaces between the particles. This

intermixing of particles of two different types

of matter on their own is called diffusion. We

also observe that on heating, diffusion

becomes faster. Why does this happen?

1.2.3 PARTICLES OF MATTER ATTRACT

EACH OTHER

Activity ______________ 1.6

• Play this game in the field— make four

groups and form human chains as

suggested:

• The first group should hold each

other from the back and lock arms

like Idu-Mishmi dancers (Fig. 1.3).

Fig. 1.3

• The second group should hold hands

to form a human chain.

• The third group should form a chain

by touching each other with only their

finger tips.

• Now, the fourth group of students

should run around and try to break the

three human chains one by one into

as many small groups as possible.

• Which group was the easiest to break?

Why?

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1.3 States of Matter

Observe different types of matter around you.

What are its different states? We can see that

matter around us exists in three different

states– solid, liquid and gas. These states of

matter arise due to the variation in the

characteristics of the particles of matter.

Now, let us study about the properties of

these three states of matter in detail.

1.3.1 THE SOLID STATE

Activity _____________ 1.9

• Collect the following articles — a pen,

a book, a needle and a piece of wooden

stick.

• Sketch the shape of the above articles

in your notebook by moving a pencil

around them.

• Do all these have a definite shape,

distinct boundaries and a fixed volume?

• What happens if they are hammered,

pulled or dropped?

• Are these capable of diffusing into each

other?

• Try compressing them by applying

force. Are you able to compress them?

All the above are examples of solids. We

can observe that all these have a definite

shape, distinct boundaries and fixed volumes,

that is, have negligible compressibility. Solids

have a tendency to maintain their shape when

subjected to outside force. Solids may break

under force but it is difficult to change their

shape, so they are rigid.

Consider the following:

(a) What about a rubber band, can it

change its shape on stretching? Is it

a solid?

(b) What about sugar and salt? When

kept in different jars these take the

shape of the jar. Are they solid?

yet we are able to compress it. Why?

All the above are solids as:

• A rubber band changes shape under

force and regains the same shape when

the force is removed. If excessive force is

applied, it breaks.

• The shape of each individual sugar or

salt crystal remains fixed, whether we

take it in our hand, put it in a plate or in

a jar.

• A sponge has minute holes, in which

air is trapped, when we press it, the air

is expelled out and we are able to

compress it.

1.3.2 THE LIQUID STATE

Activity _____________1.10

• Collect the following:

(a) water, cooking oil, milk, juice, a

cold drink.

(b) containers of different shapes. Put

a 50 mL mark on these containers

using a measuring cylinder from

the laboratory.

• What will happen if these liquids are

spilt on the floor?

• Measure 50 mL of any one liquid and

transfer it into different containers one

by one. Does the volume remain the

same?

• Does the shape of the liquid remain the

same ?

• When you pour the liquid from one

container into another, does it flow

easily?

We observe that liquids have no fixed

shape but have a fixed volume. They take up

the shape of the container in which they are

kept. Liquids flow and change shape, so they

are not rigid but can be called fluid.

Refer to activities 1.4 and 1.5 where we

saw that solids and liquids can diffuse into

liquids. The gases from the atmosphere

diffuse and dissolve in water. These gases,

especially oxygen and carbon dioxide, are

essential for the survival of aquatic animals

and plants.

All living creatures need to breathe for

survival. The aquatic animals can breathe

under water due to the presence of dissolved

oxygen in water. Thus, we may conclude that

solids, liquids and gases can diffuse into

liquids. The rate of diffusion of liquids is

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MATTER IN OUR SURROUNDINGS 5

higher than that of solids. This is due to the

fact that in the liquid state, particles move

freely and have greater space between each

other as compared to particles in the solid

state.

1.3.3 THE GASEOUS STATE

Have you ever observed a balloon seller filling

a large number of balloons from a single

cylinder of gas? Enquire from him how many

balloons is he able to fill from one cylinder.

Ask him which gas does he have in the cylinder.

Activity _____________ 1.11

• Take three 100 mL syringes and close

their nozzles by rubber corks, as

shown in Fig.1.4.

• Remove the pistons from all the

syringes.

• Leaving one syringe untouched, fill

water in the second and pieces of chalk

in the third.

• Insert the pistons back into the

syringes. You may apply some vaseline

on the pistons before inserting them

into the syringes for their smooth

movement.

• Now, try to compress the content by

pushing the piston in each syringe.

We have observed that gases are highly

compressible as compared to solids and

liquids. The liquefied petroleum gas (LPG)

cylinder that we get in our home for cooking

or the oxygen supplied to hospitals in

cylinders is compressed gas. Compressed

natural gas (CNG) is used as fuel these days

in vehicles. Due to its high compressibility,

large volumes of a gas can be compressed

into a small cylinder and transported easily.

We come to know of what is being cooked

in the kitchen without even entering there,

by the smell that reaches our nostrils. How

does this smell reach us? The particles of the

aroma of food mix with the particles of air

spread from the kitchen, reach us and even

farther away. The smell of hot cooked food

reaches us in seconds; compar

e this with the

rate of diffusion of solids and liquids. Due to

high speed of particles and large space

between them, gases show the property of

diffusing very fast into other gases.

In the gaseous state, the particles move

about randomly at high speed. Due to this

random movement, the particles hit each

other and also the walls of the container. The

pressure exerted by the gas is because of this

force exerted by gas particles per unit area

on the walls of the container.

Fig. 1.4

• What do you observe? In which case

was the piston easily pushed in?

• What do you infer from your

observations?

Fig.1.5: a, b and c show the magnified schematic

pictures of the three states of matter. The

motion of the particles can be seen and

compared in the three states of matter.

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SCIENCE6

1.4.1 EFFECT OF CHANGE

OF TEMPERATURE

Activity _____________ 1.12

• Take about 150 g of ice in a beaker and

suspend a laboratory thermometer so

that its bulb is in contact with the ice,

as in Fig. 1.6.

uestions

1. The mass per unit volume of a

substance is called density.

(density = mass/volume).

Arrange the following in order of

increasing density – air, exhaust

from chimneys, honey, water,

chalk, cotton and iron.

2. (a) Tabulate the differences in

the characterisitcs of states

of matter.

(b) Comment upon the following:

rigidity, compressibility,

fluidity, filling a gas

container, shape, kinetic

energy and density.

3. Give reasons

(a) A gas fills completely the

vessel in which it is kept.

(b) A gas exerts pressure on the

walls of the container.

called a solid.

(d) We can easily move our hand

in air but to do the same

through a solid block of wood

we need a karate expert.

4. Liquids generally have lower

density as compared to solids.

But you must have observed that

ice floats on water. Find out why.

1.4 Can Matter Change its State?

We all know from our observation that water

can exist in three states of matter–

• solid, as ice,

• liquid, as the familiar water, and

• gas, as water vapour.

What happens inside the matter during

this change of state? What happens to the

particles of matter during the change of

states? How does this change of state take

place? We need answers to these questions,

isn’t it?

(a)

(b)

Fig. 1.6: (a) Conversion of ice to water, (b) conversion

of water to water vapour

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MATTER IN OUR SURROUNDINGS 7

• Start heating the beaker on a low flame.

• Note the temperature when the ice

starts melting.

• Note the temperature when all the ice

has converted into water.

• Record your observations for this

conversion of solid to liquid state.

• Now, put a glass rod in the beaker and

heat while stirring till the water starts

boiling.

• Keep a careful eye on the thermometer

reading till most of the water has

vaporised.

• Record your observations for the

conversion of water in the liquid state

to the gaseous state.

On increasing the temperature of solids,

the kinetic energy of the particles increases.

Due to the increase in kinetic energy, the

particles start vibrating with greater speed.

The energy supplied by heat overcomes the

forces of attraction between the particles. The

particles leave their fixed positions and start

moving more freely. A stage is r

eached when

the solid melts and is converted to a liquid.

The minimum temperature at which a solid

melts to become a liquid at the atmospheric

pressure is called its melting point.

The melting point of a solid is an indication

of the strength of the force of attraction

between its particles.

The melting point of ice is 273.15 K*. The

process of melting, that is, change of solid

state into liquid state is also known as fusion.

When a solid melts, its temperature

remains the same, so where does the heat

energy go?

You must have observed, during the

experiment of melting, that the temperature

of the system does not change after the

melting point is reached, till all the ice melts.

This happens even though we continue to

heat the beaker, that is, we continue to supply

heat. This heat gets used up in changing the

state by overcoming the forces of attraction

between the particles. As this heat energy is

absorbed by ice without showing any rise in

temperature, it is considered that it gets

hidden into the contents of the beaker and is

known as the latent heat. The word latent

means hidden. The amount of heat energy

that is required to change 1 kg of a solid into

liquid at atmospheric pressure at its melting

point is known as the latent heat of fusion.

So, particles in water at 0

C (273 K) have more

energy as compared to particles in ice at the

same temperature.

When we supply heat energy to water,

particles start moving even faster. At a certain

temperature, a point is reached when the

particles have enough energy to break free

from the forces of attraction of each other. At

this temperature the liquid starts changing

into gas. The temperature at which a liquid

starts boiling at the atmospheric pressure is

known as its boiling point. Boiling is a bulk

phenomenon. Particles from the bulk of the

liquid gain enough energy to change into the

vapour state.

For water this temperature is 373 K

(100

C = 273 + 100 = 373 K).

Can you define the latent heat of

vaporisation? Do it in the same way as we

have defined the latent heat of fusion.

Particles in steam, that is, water vapour at

373 K (100

C) have more energy than water

at the same temperature. This is because

particles in steam have absorbed extra energy

in the form of latent heat of vaporisation.

*Note: Kelvin is the SI unit of temperature, 0

C =273.15 K. For convenience, we take 0

C = 273 K after

rounding off the decimal. To change a temperature on the Kelvin scale to the Celsius scale you

have to subtract 273 from the given temperature, and to convert a temperature on the Celsius

scale to the Kelvin scale you have to add 273 to the given temperature.

So, we infer that the state of matter can

be changed into another state by changing

the temperature.

We have learnt that substances around

us change state from solid to liquid and from

liquid to gas on application of heat. But there

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SCIENCE8

enclosed in a cylinder? Will the particles come

closer? Do you think that increasing or

decreasing the pressure can change the state

of matter?

are some that change directly from solid state

to gaseous state and vice versa without

changing into the liquid state.

Activity _____________1.13

• Take some camphor. Crush it and put

it in a china dish.

• Put an inverted funnel over the china

dish.

• Put a cotton plug on the stem of the

funnel, as shown in Fig. 1.7.

* atmosphere (atm) is a unit of measuring pressure exerted by a gas. The unit of pressure is Pascal (Pa):

1 atmosphere = 1.01 × 10

Pa. The pressure of air in atmosphere is called atmospheric pressure. The

atmospheric pressure at sea level is 1 atmosphere, and is taken as the normal atmospheric pressure.

Fig. 1.7: Sublimation of camphor

Fig. 1.8: By applying pressure, particles of matter

can be brought close together

Applying pressure and reducing

temperature can liquefy gases.

Have you heard of solid carbon dioxide

(CO

It is stored under high pressure. Solid

gets converted directly into gaseous state

on decrease of pressure to 1 atmosphere*

without coming into liquid state. This is the

reason that solid carbon dioxide is also known

as dry ice.

Thus, we can say that pressure and

temperature determine the state of a

substance, whether it will be solid, liquid

or gas.

• Now, heat slowly and observe.

• What do you infer from the above

activity?

A change of state directly from solid to gas

without changing into liquid state is called

sublimation and the direct change of gas to

solid without changing into liquid is called

deposition.

1.4.2 EFFECT OF CHANGE OF

PRESSURE

We have already learnt that the difference in

various states of matter is due to the

difference in the distances between the

constituent particles. What will happen when

we start putting pressure and compress a gas

Fig. 1.9: Interconversion of the three states of matter

Deposition

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MATTER IN OUR SURROUNDINGS 9

dish and keep it inside a cupboard or

on a shelf in your class.

• Record the room temperature.

• Record the time or days taken for the

evaporation process in the above cases.

• Repeat the above three steps of activity

on a rainy day and record your

observations.

• What do you infer about the effect of

temperature, surface area and wind

velocity (speed) on evaporation?

You must have observed that the rate of

evaporation increases with–

• an increase of surface area:

We know that evaporation is a surface

phenomenon. If the surface area is

increased, the rate of evaporation

increases. For example, while putting

clothes for drying up we spread them out.

• an increase of temperature:

With the increase of temperature, more

number of particles get enough kinetic

energy to go into the vapour state.

• a decrease in humidity:

Humidity is the amount of water vapour

present in air. The air around us cannot

hold more than a definite amount of

water vapour at a given temperature. If

the amount of water in air is already high,

the rate of evaporation decreases.

• an increase in wind speed:

It is a common observation that clothes

dry faster on a windy day. With the

increase in wind speed, the particles of

water vapour move away with the wind,

decreasing the amount of water vapour

in the surrounding.

1.5.2 HOW

DOES EVAPORATION CAUSE

COOLING?

In an open vessel, the liquid keeps on

evaporating. The particles of liquid absorb

energy from the surrounding to regain the

energy lost during evaporation. This

absorption of energy from the surroundings

make the surroundings cold.

uestions

1. Convert the following temperature

to celsius scale:

a. 300 K b. 573 K

2. What is the physical state of

water at:

a. 250

C b. 100

C ?

3. For any substance, why does the

temperature remain constant

during the change of state?

4. Suggest a method to liquefy

atmospheric gases.

1.5 Evaporation

Do we always need to heat or change pressure

for changing the state of matter? Can you

quote some examples from everyday life where

change of state from liquid to vapour takes

place without the liquid reaching the boiling

point? Water, when left uncovered, slowly

changes into vapour. Wet clothes dry up. What

happens to water in the above two examples?

We know that particles of matter are

always moving and are never at rest. At a given

temperature in any gas, liquid or solid, there

are particles with different amounts of kinetic

energy. In the case of liquids, a small fraction

of particles at the surface, having higher

kinetic energy, is able to break away from the

forces of attraction of other particles and gets

converted into vapour. This phenomenon of

change of liquid into vapours at any

temperature below its boiling point is called

evaporation.

1.5.1 FACTORS AFFECTING

EVAPORATION

Let us understand this with an activity.

Activity _____________1.14

• Take 5 mL of water in a test tube and

keep it near a window or under a fan.

• Take 5 mL of water in an open china

dish and keep it near a window or

under a fan.

• Take 5 mL of water in an open china

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SCIENCE10

What

you have

learnt

• Matter is made up of small particles.

• The matter around us exists in three states—solid, liquid

and gas.

• The forces of attraction between the particles are maximum in

solids, intermediate in liquids and minimum in gases.

• The spaces in between the constituent particles and kinetic

energy of the particles are minimum in the case of solids,

intermediate in liquids and maximum in gases.

What happens when you pour some

acetone (nail polish remover) on your palm?

The particles gain energy from your palm or

surroundings and evaporate causing the palm

to feel cool.

After a hot sunny day, people sprinkle

water on the roof or open ground because

the large latent heat of vaporisation of water

helps to cool the hot surface.

Can you cite some more examples from

daily life where we can feel the effect of cooling

due to evaporation?

Why should we wear cotton clothes in

summer?

During summer, we perspire more

because of the mechanism of our body which

keeps us cool. We know that during

evaporation, the particles at the surface of

the liquid gain energy from the surroundings

or body surface and change into vapour. The

heat energy equal to the latent heat of

vaporisation is absorbed from the body

leaving the body cool. Cotton, being a good

absorber of water helps in absorbing the

sweat and exposing it to the atmosphere for

easy evaporation.

Why do we see water droplets on the outer

surface of a glass containing ice-cold

water?

Let us take some ice-cold water in a

tumbler. Soon we will see water droplets on

the outer surface of the tumbler. The water

vapour present in air, on coming in contact

with the cold glass of water, loses energy and

gets converted to liquid state, which we see

as water droplets.

uestions

1. Why does a desert cooler cool

better on a hot dry day?

2. How does the water kept in an

earthen pot (matka) become cool

during summer?

3. Why does our palm feel cold

when we put some acetone or

petrol or perfume on it?

4. Why are we able to sip hot tea or

milk faster from a saucer rather

than a cup?

5. What type of clothes should we

wear in summer?

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MATTER IN OUR SURROUNDINGS 11

• The arrangement of particles is most ordered in the case of

solids, in the case of liquids layers of particles can slip and

slide over each other while for gases, there is no order,

particles just move about randomly.

• The states of matter are inter-convertible. The state of matter

can be changed by changing temperature or pressure.

• Sublimation is the change of solid state directly to gaseous

state without going through liquid state.

• Deposition is the change of gaseous state directly to solid

state without going through liquid state.

• Boiling is a bulk phenomenon. Particles from the bulk

(whole) of the liquid change into vapour state.

• Evaporation is a surface phenomenon. Particles from the

surface gain enough energy to overcome the forces of attraction

present in the liquid and change into the vapour state.

• The rate of evaporation depends upon the surface area exposed

to the atmosphere, the temperature, the humidity and the

wind speed.

• Evaporation causes cooling.

• Latent heat of vaporisation is the heat energy required to change

1 kg of a liquid to gas at atmospheric pressure at its

boiling point.

• Latent heat of fusion is the amount of heat energy required

to change 1 kg of solid into liquid at its melting point.

• Some measurable quantities and their units to remember:

Quantity Unit Symbol

Temperature kelvin K

Length metre m

Mass kilogram kg

Weight newton N

Volume cubic metre m

Density kilogram per cubic metre kg m

–3

Pressure pascal Pa

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1. Convert the following temperatures to the celsius scale.

(a) 293 K (b) 470 K

2. Convert the following temperatures to the kelvin scale.

(a) 25

°C (b) 373

°C

3. Give reason for the following observations.

(a) Naphthalene balls disappear with time without leaving

any solid.

(b) We can get the smell of perfume sitting several metres

away.

4. Arrange the following substances in increasing order of forces

of attraction between the particles— water, sugar, oxygen.

5. What is the physical state of water at—

(a) 25

°C (b) 0

°C (c) 100

°C ?

6. Give two reasons to justify—

(a) water at room temperature is a liquid.

(b) an iron almirah is a solid at room temperature.

7. Why is ice at 273 K more effective in cooling than water at the

same temperature?

8. What produces more severe burns, boiling water or steam?

9. Name A,B,C,D,E and F in the following diagram showing

change in its state

Exercises

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MATTER IN OUR SURROUNDINGS 13

Group Activity

Prepare a model to demonstrate movement of particles in solids,

liquids and gases.

For making this model you will need

• A transparent jar

• A big rubber balloon or piece of stretchable rubber sheet

• A string

• Few chickpeas or black gram or dry green peas.

How to make?

• Put the seeds in the jar.

• Sew the string to the centre of the rubber sheet and put some

tape to keep it tied securely.

• Stretch and tie the rubber sheet on the mouth of the jar.

• Your model is ready. Now run your fingers up and down the

string by first tugging at it slowly and then rapidly.

Fig. 1.10: A model for converting of solid to liquid and liquid to gas.

Rationalised 2023-24