- Solid => Liquid is Melting
- Liquid => Solid is Freezing
- Liquid => Gas is Vaporization
- Gas => Liquid is Condensation
- Gas => Solid is Deposition
- Solid => Gas is Sublimation
A phase change occurs in matter when its atoms become too charged or uncharged to maintain their current state. In essense a state of matter is just the most stable way a group of atoms can group together given a certain temperature. Some people confuse a chemical reaction with a state change; this is not the case, while a chemical reaction can heat or cool a substace to cause a state change they are fundamentally different.