The Heating Curve

Figure below shows the change of the temperature when a solid is heated until it become gas.

Note:
B to C

1. Temperature remain unchanged because the heat absorbed is used to overcome the force between the particles in the solid.
2. The heat absorbed to change a solid to liquid is called the latent heat of fusion.

D to E

1. Temperature remain unchanged because the heat absorbed is used to overcome the force between the particles in the liquid and also the atmospheric pressure.
2. The heat absorbed to change a liquid to gas is called the latent heat of vaporisation.