Editing Charles's law (section)

==Relation to kinetic theory==
The [[kinetic theory of gases]] relates the [[macroscopic]] properties of gases, such as pressure and volume, to the [[microscopic]] properties of the molecules which make up the gas, particularly the mass and speed of the molecules. To derive Charles's law from kinetic theory, it is necessary to have a microscopic definition of temperature: this can be conveniently taken as the temperature being proportional to the average [[kinetic energy]] of the gas molecules, {{overline|''E''}}<sub>k</sub>:
:<math>T \propto \bar{E_{\rm k}}.\,</math>

Under this definition, the demonstration of Charles's law is almost trivial. The kinetic theory equivalent of the ideal gas law relates {{mvar|PV}} to the average kinetic energy:
:<math>PV = \frac{2}{3} N \bar{E_{\rm k}}\,</math>