1.
Matter in Our Surroundings
Chapter 1
Class-IX
Science

2.
What is matter?
Anything around us that has mass and occupy space is
matter.
E.g
 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
 Early Indian philosophers classified matter in the form of
five basic elements – the “Panch Tatva”– air, earth, fire, sky
and water

3.
1.1 Physical Nature of Matter
 Matter is made up of particles.
 Matter of a particle is extremely small.
Solid Particles Liquid particles Gas Particles
 The particles of matter are very small – they are
small beyond our imagination!!!!

4.
1.2 Characteristics of Particles of Matter
1. Particles of matter are continuously moving.
2. Particles of matter have space between them.
3. Particles of matter attract each other.
1.Particles of matter are continuously moving.
Particles of matter possess kinetic energy. As the
temperature rises, particles move faster. So, with
increases in temperature the kinetic energy of the
particles also increases.
The intermixing of particles of two different types
of matter on their own is called diffusion.

5.
Diffusion and Osmosis

6.
2. Particles of matter have space between them.
Particles of sugar, salt, Dettol, or potassium
permanganate got evenly distributed in water. And
these 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.
Solid Liquid Gas

7.
3. Particles of matter attract each other.
The particles of matter have force of attraction between
them.
This force keeps the particles together. The strength of this
force of attraction varies from one kind of matter to
another.
Force of attraction Force of attraction
Force of attraction
Solid liquid Gas
> >

8.
States/Forms of Matter
The matter around us exists in three different states–
1.Solid
2.Liquid
3.Gas.
These states of matter arise due to the variation in the
characteristics of the particles of matter.

9.
Which kind of thing can be called solid?
1.THE SOLID STATE
If a matter possesses these following properties then it is Solid.
 They have a definite shape.
 They have Distinct boundaries and fixed volumes.
 They have negligible compressibility.
 They 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.

10.
1.THE LIQUID STATE
Properties of Liquid-
They have no fixed shape but have a fixed volume.
They take up the shape of the container in which they are
kept.
The particles move freely and have greater space between
each other than Solid.
 Liquids flow and change shape, so they are not rigid but
can be called fluid.
The solids, liquids and gases can diffuse into liquids. The
rate of diffusion of liquids is higher than that of solids.

11.
3.THE GASEOUS STATE
Properties of Gas-
They have no fixed shape but have a fixed volume
Gases are highly compressible as compared to solids and liquids.
The Particles of gas have large space between them and show the
property of diffusing at faster rate.
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.

12.
Can Matter Change its State?
Yes, Variations in Temperature and pressure lead to change in states of
Matter.
EFFECT OF CHANGE OF TEMPERATURE.
 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 reached
when the solid melts and is converted to a liquid and so
liquid to gas.
 The minimum temperature at which a solid melts to
become a liquid at the atmospheric pressure is called its
melting point.
 The temperature at which a liquid starts boiling at the
atmospheric pressure is known as its boiling point.

13.
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
 The melting point of a solid is an indication of the
strength of the force of attraction between its particles.

14.
Latent heat Concept:-
Latent heat means “hidden” or heat that is hidden.
Lets take a look at this graph-
 On heating energy is absorbed by ice without showing any
rise in temperature and this heat is used up in order to
overcome the force of attraction between particles, it is
considered that it gets hidden into the contents of the beaker
and is known as the latent heat.
 So, particles in water at 0 C (273 K) have more energy as
compared to particles in ice at the same temperature.

15.
 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.
 Similarly, the amount of heat energy that is required to change 1
kg of a liquid into gas at atmospheric pressure at its boiling
point is known as the latent heat of vaporization.
 So particles in steam have absorbed extra energy in the form of
latent heat of vaporization. Hence steam has more energy than a
liquid at boiling temperature.

16.
 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.
Examples- 1. Sublimation- Camphor, Naphthalene balls
2. Deposition – Dry Ice (Solid CO2)
Sublimation and deposition

17.
1.4.2 EFFECT OF CHANGE OF PRESSURE
State of matter is dependent on pressure variations.
On increasing pressure in given cylinder the gas particles of matter
bring close to each other this lead to changes in state of matter, i.e
Gas to liquid, further liquid into solid.
However, it is extremely difficult to change liquid into solid by
applying pressure only.

18.
PREPARATION OF DRY ICE(Solid CO2)
We know the variations in temperature and pressure lead to change in
states of matter.
Thus, applying pressure and reducing temperature can liquefy gases as well
as solidify.
 CO2 is compressed at high pressure and at the same time temperature
also decrease.
 On compression the particles of CO2 come closer to each other and by
lowering the temperature the particles loses kinetic energy, these lead to
deposition of CO2 liquid into Solid Ice.
 And Solid CO2 gets converted directly to 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.

19.
Interconversion of the three states of matter
We know the variations in temperature and pressure lead to
change in state of matter.
 Increase in pressure and decrease in temperature or
decrease in pressure and increase in temperature cause
interconversion of the three states of matter.

20.
Evaporation
 It is process where change of state from liquid to vapour
takes place without the liquid reaching the boiling point is
known as evaporation.
 At a given temperature in any gas, liquid or solid, 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 without
reaching boiling point.
Examples- Wet clothes dry up
Evaporation

21.
Factors that effect the rate of evaporation-
 An increase of surface area.
 An increase of temperature.
 A decrease in humidity(Amount of
Moisture).
 An increase in wind speed.
HOW DOES EVAPORATION CAUSE COOLING?
 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.
Examples-
1. Pouring some acetone on your palm leaving cool
effect.
2. Sprinkling water on the roof or open ground helps to cool the
hot surface.

22.
Why should we wear cotton clothes in summer?
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 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.

23.
Why do we see water droplets on the outer surface of
a glass containing ice-cold water?
 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.

24.
-----The End-----
Thankyou!