# During what type of phase change does a substance release energy to its surroundings?

##### 1 Answer
Apr 19, 2016

Freezing and Condensation

#### Explanation:

There are two phase changes where the heat energy is released: Condensation: When gas condenses to liquid the quantity of energy converted from chemical to heat is called the Heat of Vaporization or Δ ${H}_{v a p}$.

As the gas particles cool down ,the particles slow down, and a liquid forms. The droplets of water seen on a mirror when you exhale come from water vapor (in your breather) that cools enough to condense and collect on the mirror.

When a liquid becomes a solid (freeze), heat energy is generally lost (given off).