2. MATTER
Matter is anything that occupies space
and has volume . In other words , they
have only mass and volume .
For eg.. The pen with which we write ,
notebooks etc are all made up of matter .
4. In Solids, The particles are packed closely
together. The forces between particles are strong
enough so that the particles cannot move freely .
As a result, a solid has a stable, definite shape,
and a definite volume.
A liquid is a nearly incompressible fluid that takes
the shape of its container but has a fixed volume.
Intermolecular space is more in liquids than in
solids.
A gas is a compressible fluid. A gas takes the
shape of its container andit will also fill the
container . In a gas, intermolecular space is
much greater than solids and liquids
5. MELTING POINT & BOILING POINT
Melting Point
The temp. at which a solid melts to
become a liquid at the atmospheric
pressure is called its melting point.
The melting point of ice is 273.16 k .
The state of melting is also known as
“ fusion “
Boiling Point
The temp. at which a liquid boils to
became a gas at the atmospheric
pressure is called its boiling point.
6. 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.
7. Evaporation
The phenomenon of change of a liquid
into vapours at any temp. below its boiling
point is called evaporation
8. Factors affecting evaporation:
1.Surface area :
if the surface area is increased , the rate of
evaporation will also increase ,,, for eg .
While putting clothes for drying up we
spread them out
9. 2 . Temperature :
With the increase in temperature , the rate of
evaporation also increases
3 . Humidity :
Humidity is the amount of water vapour present
in in air … if the amount of vapour in air
increases , the rate of evaporation decreases.
For eg , a dessert cooler cools better on a dry
day as compared to a humod day
10. EVAPORATION CAUSES
COOLING
Evaporation is the conversion of water to vapour at a temperature
below boiling point.
Water has a 'Vapour Pressure' at any temperature below 100°C at
atmospheric pressure. (At the boiling point, water is NOT
evaporating, it's Vaporising. Evaporation takes place below the
boiling temperature).
The molecules leaving the water as vapour are moved away by any
movement of air above the water and therefore cannot return to the
water. The Energy required to evaporate the water is called 'Latent
Heat' and takes place by removing the necessary heat from the
water as 'Sensible Heat' thereby decreasing the water temperature.
