# Avogadro's Law

Equal volumes of an ideal gas contain equal numbers of molecules, if both volumes are at the same temperature and pressure. For example, 1 L of ideal gas contains twice as many molecules as 0.5 L of ideal gas at the same temperature and pressure.

It is, in fact, only true for ideal gases.

**See also: **Avogadro, Armedeo, Dalton′s Law of Partial Pressures.

**Subjects: ** Physics