Avogadro's hypothesis

In chemistry, the law stating that equal volumes of all gases, when at the same temperature and pressure, have the same numbers of molecules. One mole of any gas contains 6.023 × 10²³ particles and occupies 24 dm³ at room temperature and pressure. The type of gas does not make any difference. The law was first put forward by Italian chemist Amedeo Avogadro.