Topics > Matter & Measurements > States of Matter

States of matter are the different physical forms in which matter can exist. Matter can exist as a solid, liquid, or gas, depending on the arrangement and movement of its particles.

Solids have a fixed shape and volume. The particles in a solid are tightly packed and held together by strong intermolecular forces, resulting in a rigid structure. They vibrate in place but do not move freely.

• • Important properties often emphasized with solids: density, hardness, and melting point.

Liquids have a definite volume but no fixed shape. The particles in a liquid are close together, but they have more freedom of movement compared to solids. They can slide past each other, allowing liquids to flow and take the shape of their containers.

• • Important properties often emphasized with liquids: viscosity, surface tension, and boiling point.

Gases have neither a fixed shape nor volume. The particles in a gas are far apart and move randomly and rapidly. They have high kinetic energy (move fast), enabling them to occupy the entire volume of their container and exert pressure on its walls.

• • Important properties often emphasized with gases: compressibility, pressure, and temperature.