Phase changes occur when the state of matter of a substance changes. This can happen when the temperature or pressure of the substance is changed. There are three common phase changes:

Melting occurs when a solid turns into a liquid. This happens when the temperature of the solid is increased.

Freezing occurs when a liquid turns into a solid. This happens when the temperature of the liquid is decreased.

Vaporization occurs when a liquid turns into a gas. This happens when the temperature of the liquid is increased.

Condensation occurs when a gas turns into a liquid. This happens when the temperature of the gas is decreased.