States of Matter and Phase Transitions: Chemistry Key Concepts

Solid

Molecules are arranged in regular, repeating patterns, held firmly in place, and can only vibrate within a limited area

. Liquid

Molecules flow easily around one another but are kept from flying apart by attractive forces; they assume the shape of their container

. Gas

Molecules fly in all directions at great speeds with attractive forces between them being insignificant

. Plasma

A state of matter at very high temperatures where atoms lose their electrons, resulting in a mixture of electrons and nuclei

. Melting

The phase transition from a solid to a liquid

. Freezing

The phase transition from a liquid to a solid

. Vaporization (Boiling)

The phase transition from a liquid to a gas

. Condensation

The phase transition from a gas to a liquid

. Sublimation

The phase transition from a solid directly to a gas

. Deposition

The phase transition from a gas directly to a solid

. Ionization

The process of a gas becoming a plasma

. Deionization

The process of a plasma becoming a gas

. Phase Diagram

A graphical way to depict the effects of pressure and temperature on the phase of a substance

. Triple Point

The specific temperature and pressure where all three phases (solid, liquid, and gas) exist in equilibrium

. Critical Point

The temperature above which a gas cannot be liquefied, no matter how much pressure is applied

. Supercritical Fluid

A substance beyond the critical point that is indistinguishable between a gas and a liquid