Avogadro's law states that equal volumes of all gases, at the same temperature and pressure, contain the same number of molecules, which is a fundamental principle of ideal gas behavior.
The claim states a fundamental scientific principle taught at the introductory level, namely that one mole of any ideal gas occupies the same volume at standard temperature and pressure (approx 22.4 liters). This is a foundational definition within thermodynamics and ideal gas theory, qualifying it as common knowledge that requires no specific journal citation to verify.