Internal energy in phase transition

During a change of phase the temperature does not change, but the internal energy does. The internal energy is the sum of the kinetic energy of the molecules and the chemical potential energy of the molecules. During a change of phase, the average kinetic energy of the molecules stays the same (with the temperature), but the average potential energy changes.

For more information on this topic, do visit:

http://electron6.phys.utk.edu/101/CH7/phase_transitions.htm&ei=cJxiShax&lc=en-IN&s=1&m=364&ts=1436773479&sig=AKQ9UO84sBHgLYBnocfErpK9LfMYP6vfkQ