1. types of burning
1.1. combustion
1.1.1. the burning of substances in the air
1.2. incombustable
1.2.1. which do not catch fire in the air
2. sources of heat energy
2.1. sun
2.2. earth
2.3. wood and biomass
2.4. coal and petroleum
3. units of heat
3.1. joules
3.2. ergs
3.2.1. one joule= 10 to the power seven
3.3. calories
3.3.1. 1 cal= 4.2 joules
4. definition
4.1. heat is an invisible energy, which causes a sensation of heat or coldness
5. effects of heat
5.1. it brings about a change in the temperature
5.2. change in dimensions
5.3. change in state
5.3.1. change of state
5.3.1.1. because of the absorption or release of heat the substance changes its physical state
5.3.2. melting
5.3.2.1. melting point
5.3.2.1.1. the fixed temperature at which melting happens
5.3.2.2. when the solid changes to liquid by absorption of heat
5.3.3. freezing
5.3.3.1. when a liquid on cooling changes from solid to liquid with the release of heat energy
5.3.3.2. freezing point
5.3.3.2.1. the fixed temperature at which a liquid changes to solid
5.3.4. boiling
5.3.4.1. when a liquid changes to gaseous state with absorption of heat
5.3.4.2. boiling point
5.3.4.2.1. the fixed temperature at which a liquid changes to gaseous state
5.3.5. condensation
5.3.5.1. when a gas changes into liquid with the release of heat
5.3.5.2. condensation point
5.3.5.2.1. the fixed temperature at which a gas changes into liquid
5.3.6. evaporation
5.3.6.1. the change of liquid from liquid to gas below the boiling point
5.3.7. sublimation
5.3.7.1. when a solid changes to gas without changing into liquid on heating
5.3.7.2. the substance which can sublimate are called sublime