Sublimation, when a solid transforms into a gas, is an endothermic phrase change, while deposition, when a gas transforms to a solid, is an exothermic phase change. There are a total of six phase changes in matter, and three are endothermic and three are exothermic. An endothermic phase change absorbs heat or energy, while an exothermic phase change releases heat or energy, states the Washington University Department of Chemistry.
The following are additional endothermic phase changes:
- Fusion, or melting, when a solid transforms to liquid
- Vaporization, when a liquid transforms to gas
The following are exothermic phase changes:
- Freezing, when a liquid transforms to solid
- Condensation, when a gas transforms to liquid
In endothermic phase changes, intermolecular binds are broken, requiring energy. This is the energy that is absorbed. In exothermic phase changes, molecules bind to each other in a formation that requires less energy. Therefore, this energy is expelled.