Grade IX science L.no.1.matter in our surrounding

Grade IX-Science(Ncert)
1.Matter
in our
surrounding

Matter in our surrounding
Introduction:
As we look at our surrounding, 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”.
Anything that occupies space and has mass is called matter.
Early Indian philosophers classified matter in the form
of five basic elements the “Panch Tatva”
– Air, Earth, Fire , Sky and Water.

Matter in our surrounding
Matter:
Modern day scientists have evolved two types of
classification of matter based on their physical properties
and chemical nature.
In this chapter we shall learn about matter based on its
physical properties.

1.1 Physical properties of matter
1.1.1 Matter is made up of particles
Activity-Take some water in a beaker and note its level.Dissolve some
salt or sugar in it with the help of glass rod.The salt dissolves in the
water does not change.
Observation-The particles of salt or sugar get into the space between
the particles of water.
Conclusion-Matter is made up of particles.

1.1 Physical properties of matter
1.1.2 How small are these particles of matter?
Activity-Dissolve 2-3 crystals of potassium permanganate in 100 ml
water in a beaker. Take 10 ml of this solution and dissolve in 100 ml of
water. Take 10 ml of this solution and dissolve in 100ml of water.
Observation-This shows that a few crystals of potassium
permanganate can colour a large volume of water because there are
millions of tiny particles in each crystal.
Conclusion-Matter is made up of tiny particles.

1.2 Characteristics of particles of matter.
1.2.1 Particles of matter have space between them
Example-When we make tea ,coffee or lemonade(nimbu
pani),particles of one type of matter get into spaces between particles
of another. This shows that there is enough space between particles
of matter.

1.2.2 Particles of matter are continuously moving.
Example- Take some water in a beaker and put a drop of blue or red
ink slowly along the sides of beaker. Leave it undisturbed for few
hours.The ink spreads evenly throughout the water due to the
movement of the particles of ink and water.
This shows that particles of matter are continuously moving.

1.2.1 Particles of matter are continuously moving.
Diffusion:
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.

1.2.3 Particles of matter attract each other.
Example- Take an iron nail, a piece of chalk and a rubber band. Try
breaking them by hammering ,cutting or stretching. It is more easier
to break the chalk, less easier to break the rubber band and difficult
to break the iron nail.This is because the particles in the iron nail are
held together with greater force than in the rubber band or chalk.

1.3 States of Matter
States of
matter
Solids Liquids Gaseous

1.3 States of Matter-Properties of Solids
i) Solids have definite shapes and fixed volume.
ii) The space between the particle is minimum.
iii) The force of attraction between the particles is maximum.
iv) The movement of the particles is minimum.
v) They are least compressible.

1.3 States of Matter-Properties of Liquids
i) Liquids have no definite shape but have fixed volume. Liquids take the
shape of the container.
ii) The space between the particles is intermediate
iii) The force of attraction between the particles is intermediate.
iv) The movement of the particles is intermediate.
v) They are less compressible.

1.3 States of Matter-Properties of Gaseous state
i) Gases have no definite shape or fixed volume. Gases occupy the
whole space of the container.
ii) The space between the particles is maximum.
iii) The force of attraction between the particles is minimum.
iv) The movement of the particles is maximum.
v) They are most compressible.

1.4 Can matter change its state?
Physical states of matter can be interconverted into each
other by following two ways:
1. By changing the temperature
2. By changing the pressure
Physical states
of matter
By changing the
Temperature
By changing the
Pressure

1.4.1 Effect of change in Temperature:
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.
(a) Conversion of ice to water (b) Conversion of water to water vapour

1. Effect of Change of Temperature:
Solid to liquid:
On increasing the temperature of solids, the kinetic energy of the particles
increases which overcomes the forces of attraction between the particles
there by solid gets converted to a liquid.
Melting: Change of solid state of a substance into liquid is called Melting.
Melting point: The temperature at which a solid melts to become a liquid at
the atmospheric pressure is called its Melting point.
Melting point of ice is 0oc /273.15 K

(a) Liquid to gas:
On heating a liquid like water, the kinetic energy of its particles increases
as high as in a gas, thus causing the liquid to change to a gas.
Boiling: The change of a liquid substance into gas on heating is called
Boiling.
Boiling point: The temperature at which a liquid boils and changes rapidly
into a gas at the atmospheric pressure is called its
Boiling point.
Boiling point of water is 100oC.
.

(b) Gas to liquid:
On cooling a gas like steam (or water vapour), the kinetic energy of its
particles is lowered down, causing them to move slowly and bringing
them closer, forming a liquid.
Condensation: The process, in which a gas, on cooling, turns into a liquid
at a specific temperature is called condensation or liquefaction..

(c) Liquid to solid:
When a liquid is cooled down by lowering its temperature, its particles
lose the kinetic energy and come to a stationary position, causing the
liquid to turn to solid.
Freezing: The change of a liquid substance into solid by lowering its
temperature is called freezing.
Freezing point: The temperature at which the state
of a substance changes from a liquid to a solid is
called the freezing point of that substance.

Fusion: The process of melting i.e change of solid state into liquid state is also
known as Fusion.
Latent heat: The heat energy that is required to change the state of a substance
without causing any rise in the temperature of the substance is called latent heat.
Since, the heat energy is hidden in the bulk of the matter, it is called latent heat.
Latent heat of fusion: The heat energy required to convert 1 kilogram of a solid
into liquid at atmospheric pressure, at its melting point, is known as the latent
heat of fusion

Latent heat of vaporisation: The heat energy
required to convert 1 kilogram of liquid into gas, at
atmospheric pressure, at its boiling point, is known
as the Latent heat of vaporisation

Sublimation: The change of state of a substance
directly from a solid to gas or gas to solid, without
changing into the liquid state, is called Sublimation.
Eg-Camphor,Napthalene balls

1.4.2 Effect of change in Pressure:
Gas to liquid: Gases can be liquefied by applying pressure and reducing
the temperature.
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.
Thus, we can say that pressure and temperature determine the state of a
substance, whether it will be solid, liquid or gas.

1.5 Evaporation
Evaporation:
The process of conversion of a substance from the liquid
state to the gaseous state at any temperature below its
boiling point is called Evaporation or Vaporisation.

ii.Temperature: The rate of
evaporation increases with an
increase in temperature.
Eg- Boiling water evaporates faster
than fresh tap water.
15.1 Factors affecting rate of evaporation
i.Surface area: The rate of
evaporation increases on increasing
the surface area of the liquid.
Eg- We spread out clothes to dry. We
do that because that speeds up the
process of vaporization.

iv.Wind speed: An increase in the
wind speed increases the rate of
evaporation.
• For example, we use hand dryers
to dry our hands. Here the wind
is expelled from the hand dryer
which dries our hand.
iii.Humidity: Decrease in the
humidity increases the rate of
evaporation.
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.
15.1 Factors affecting rate of evaporation

Why should we wear cotton clothes in summer ?
Solution-During summer season, we sweat a lot. Cotton is a
good absorber of water. It allows better air circulation. Thus,
it absorbs sweat from our body and exposes the sweat to the
atmosphere ,making its evaporation faster.
15.2 How does Evaporation cause cooling?

Why do we see water droplets on the outer surface of a glass
containing ice-cold water?
Activity-Let us take some ice-cold water in a tumbler.
Observation-Soon we will see water droplets on the outer
surface of the tumbler.
Conclusion-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.
15.2 How does Evaporation cause cooling?

Grade IX science L.no.1.matter in our surrounding

Grade IX science L.no.1.matter in our surrounding

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