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Latent heat and molecular behaviour

During a change of state (e.g. from a solid to liquid), the thermal energy absorbed by a substance goes into weakening or strengthening the intermolecular bonds.

Intermolecular bonds are weak forces that keep molecules in many solids and, to a lesser extent, in liquids close together.

The water molecules in ice are held together by intermolecular bonds.

The energy absorbed during a change of state does not increase the random kinetic energy of the particles.

For this reason the temperature of a substance is constant while it changes state.

The internal energy still changes during a change of state as the potential energy of the particles changes.

If a substance continues to absorb energy after the change of state, the random kinetic energy of its particles will start to increase again.

Ice changing into liquid water. This happens at a temperature of $0^{\circ}\text{C}$