Effects of heat
● When a body is heated , it brings about some changes in its properties called Effects of heat
● When heat is imparted to ice its Temperature will increase. At 0 degree centigrade, state will change ice melts . Water now at 0 degree centigrade, further heating will rise the temperature of water. At 100 degree centigrade change of state takes place from water to water vapour.
● Effects are-1. Change in temperature
2. Change in State
3. Change in shape ( Thermal Expansion)
● Factors affecting Change in temperature-
1. Heat imparted
2. Mass of the body
3. Nature of the material of the body
● Change of state takes place when heat is either imparted or taken away from the body at particular temperature.
1. Solid to liquid - Melting
2. Liquid to Solid - Freezing
3. Liquid to Gas - Vaporization
4. Gas to Liquid- Condensation
5. Solid to Gas - Sublimation
6. Gas to Solid - deposition
● Change in shape of a body may occur due to heat . Body expands on heating.
● Thermal Expansion- Expansion in a body on heating
Change of state
● Heat can change state of matter.
● change of state
Important terms associated
1. Melting / Boiling/ Evaporation
2. Boiling point/ Melting point/
3. Latent heat of Fusion
4. Latent heat of vaporisation
●Melting / Boiling/ Evaporation/ Condensation:-
When a solid is heated it changes into liquid at a fixed temperature this process is called melting.
When the liquid freezes into solid at a particular temperature called freezing or fusion .
When a liquid is heated it change it into vapour at a fixed temperature this process is called boiling or vaporization .
When the vapour condenses into liquid at the fixed temperature the process is called condensation
● Boiling point/ Melting point
The constant temperature at which a solid melts is called its melting point and the constant temperature is at which a liquid boils is called boiling point. Melting point and Boiling point a characteristic properties of the matter
● Latent heat of Fusion
The latent heat of fusion is defined as the amount of heat gained by a solid object to convert into liquid form without the change in the temperature.
●Latent heat of vaporisation
The latent heat of fusion is defined as the amount of heat gained by a liquid tto convert into gas form without the change in the temperature.
Thermal Expansion
● Expansion of a substance on heating is called the Thermal Expansion.
● Types-
1. Linear Expansion ( increase in length on heating)
☆ Factors affecting linear Expansion:-
i) material of wire/rod
ii) original length
Iii) rise in temperature
2. Superficial Expansion ( increase in area on heating)
☆ Factors affecting superficial Expansion
i) material of sheet/ surface
ii) original Area
Iii) rise in temperature
3. Cubical Expansion ( increase in volume on heating)
☆Factors affecting cubical Expansion
i) nature of material
ii) original volume
Iii) rise in temperature
●Liquids expand more than solids and Gases expand more than Liquids.
● Expansivity of a substance is constant. Expansivity of different substances are diferent.
● Relation between coefficient of linear Expansion , coefficient of superficial Expansion and coefficient of cubical Expansion is
α = coefficient of linear expansion
β = coefficient of areal expansion
γ = coefficient of volume expansion
α = β /2= γ /3
● Due to differences in Expansivity of metals, a bimetallic strip bend on heating. This property of bimetallic strips is used in thermostats
Thermostat is a device used to control temperature by making and breaking the circuit, .used in electric iron , oven , refrigerator etc.
● Invar , an alloy of iron and nickel has negligible coefficient of expansion so used in pendulum
1.To know more go to the post transfer of heat
2.To check your knowledge question - Answer
