According to Avogadro's principle, equal volumes of gases at the same conditions of temperature and pressure have equal:

Avogadro's principle states that equal volumes of gases, when measured at the same temperature and pressure, contain equal numbers of molecules. This is a fundamental concept in gas laws and illustrates that the volume of a gas is directly related to the number of its particles, assuming ideal behavior.

To further elaborate, when gases are allowed to expand or compress under the same conditions of temperature and pressure, the amount of substance, or number of molecules, determines how much space the gas occupies. Thus, if two different gases are at the same temperature and pressure and occupy the same volume, it follows that they must consist of the same number of molecules, regardless of their identity or mass.

This understanding is essential for calculations involving gases in chemical reactions and stoichiometry, where the mole concept connects to volume under defined conditions. This principle highlights the relationship between physical properties and the molecular nature of gases, strengthening our grasp of the behavior of gases in the context of the kinetic molecular theory.