What Are the Four Phases of Matter?

The four phases of matter are solid, liquid, gas and plasma. Substances can move between these states of matter based on changes in pressure and temperature.

As temperature increases, a solid turns into a liquid by melting, and a liquid turns into gas by vaporization. A gas can turn into plasma through the process of ionization, while the reverse occurs through deionization. In the other direction, a gas becomes a liquid via condensation, which becomes a solid by freezing. In addition to the traditional four phases, some non-classical states of matter include glass, liquid crystal states, quantum spin liquid, superfluids and degenerate matter.