CLASS 9 MATTER IN OUR SURROUNDINGS
Ch-1. Matter in our surroundings
Notes Matter
* Everything in this universe is made up of material which is called matter.
Matter is anything which occupies mass and space.
* Each matter is a collection of lots of tiny particles.
* Each matter is are continuously moving
* A matter may exist in three forms or states namely solid, liquid, gas
Characteristics of matter
✤ Solid State
→ Solid have definite shape.
→ Solid have distinct boundaries.
→ Solid have rigidity
→ Solid have incompressibility.
→ Solid have fixed volume.
✤ Liquid state
→ The liquid shows fluidity.
→ Liquid have low compressibility.
→ Liquid have not definite boundary or shape but fixed volume
✤ Gas State
→ Gas have fluidity.
→ Gas have high compressibility.
→ Gas have not definite boundary, volume or Shape
→ Particles of matter are closely packed in solids, loosely
→ Particles of matter attract each other. The force of attraction between particles
is called intermolecular force of attraction.
The intermolecular force of attraction is affected by temperature and
pressure. Thus the state of matter can be changed by changing temperature
and pressure.
✤ Melting point
• Melting point is the temperature at which is solid becomes a liquid at
atmospheric pressure.
• Latent heat of fusion is the amount of heat consumed when 1 kg of a solid
changes into liquid at a constant temperature.
✤ Boiling point
→ Boiling point is the temperature at which a liquid changes into its vapor at
atmospheric pressure.
→ Latent heat of fusion vaporisation is the amount of heat consumed when 1 kg
of liquid charges into vapor at constant temperature.
✤ Sumblimation
→ Sumblimation is the changes of state directly from solid to gaseous state
whereas the change of gaseous state directly to solid state without going to
the liquid state is called sumblimation. deposition.
✤ Evaporation
→ Evaporation is a surface phenomenon in which a liquid changes into
vapours/gas below its boiling point.
→ Evaporation results in lowering of temperature, i.e., self cooling is caused
when evaporation takes place.
✤ 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 Solid,
intermediate in liquids and minimum in gases.
• The spaces in between the constituent particles and kinetic energy of the
particles are minimum in the care of Solids, intermediate in liquids and
maximum in gases.
• 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 on pressure.
• Sublimation is the change of gaseous state directly to Solid state without going
through liquid state, and vice versa.
• 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 1kg of a
liquid to gas at atmosphere pressure at its boiling point.
• Latent heat of fussion is the amount of heat energy required to change 1kg of
solid into liquid at its melting point.
ACTIVITY
{Particles of matter magnified millions of time}
Steps :-
❆ Take 100ml 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.
Steps :-
❆ Take some camphor or ammonium chloride- crush it and put it in a china
dish.
❆ Put an interval funnel over the china dish.
❆ Put a cotton plug on the stem of the funnel, shown in the figure.
❆ Now, heat slowly and observe.
