**A) Definition** : heat is a form of energy. it measured in calories and B.T.U(Fahrenheit = 1 b.t.u )**B) Units**:

Calory : the amount of heat require to raise 1 degree temp of 1 gram water is called 1 calory.

B.T.U : Energy require to raise 1 degree temp of 1 pound water . (1 B.T.U = 1 Fahrenheit )

**C) Specific heat** : energy required to raise 1 degree of any 1 gm substance.

**D) Latent heat** : 1. Latent heat of vaporization.

2. Latent heat of freezing

**Latent heat of vaporization** : amount of heat required to convert 1 gm of water in to vapor is called latent heat of vaporization of water.(at 100 degree , 540 calories/gm needed for water)

**Latent heat of freezing**: amount of heat required to convert 1 gm of water in to solid ice is called latent heat of vaporization of water.(at 0 degree , 80 calories/gm needed to convert water to ice)

**TRANSMISSION OF HEAT**

**1) Conduction**

The heat travels through the molecule of substance without movement of molecule themselves.(molecule doesn’t travels.)

**2) Convection :**