Gay-Lussac's law gases and the gaseous products can be expressed in simple whole numbers. For example, Gay-Lussac found that 2 volumes of hydrogen and 1 volume of oxygen would react to form 2 volumes of gaseous water. Based on Gay-Lussac's results, Amedeo Avogadro theorized that, at the same temperature and pressure, equal volumes of gas contain equal numbers of molecules (Avogadro's law). This hypothesis meant that the previously stated result could also be expressed as The law of combining gases was made public by Joseph Louis Gay-Lussac in 1808. Avogadro's hypothesis, however, was not initially accepted by chemists until the Italian chemist
Kinetic theory of gases "K": This is a first non-trivial result of the kinetic theory because it relates pressure, a macroscopic property, to the (translational) kinetic energy of the molecules formula_12, which is a microscopic property. Rewriting the above result for the pressure as formula_13, we may combine it with the ideal gas law where formula_14 is the Boltzmann constant and formula_15 the absolute temperature defined by the ideal gas law, to obtain which leads to simplified expression of the average kinetic energy per molecule, The kinetic energy of the system is N times that of a molecule, namely formula_18. Then the temperature formula_15