Phase transition

A phase transition is a change of matter from one phase to another. Phases can include gas, liquid, and solid or can also refer to characteristics such as crystal structure or superconductivity.

The distinguishing characteristic of a phase transition is a suddenly change in the behavior of a material when a thermodynamic variable such as pressure or temperature is changed. For example, water changes suddenly when the temperature is changed from below its melting point to above its melting point.

A first-order phase transition such as melting or boiling involves the release or absorption of energy. A second-order phase transition occurs without energy release.

A phase transition occurs when one structure suddenly becomes more energetically favorable than another.