• id: JTHERM-02-N01
• title: Postulates of the Kinetic Theory of Gases
• tags: kinetic-theory, assumptions, ideal-gas

The kinetic theory models a gas as a large number $N$ of identical molecules of mass $m$, treated as point particles. They move randomly with all directions equally probable (isotropic motion). Intermolecular forces are negligible except during brief elastic collisions. The time of a collision is much shorter than the time between collisions. These assumptions lead directly to the ideal gas law $PV = Nk_BT$. Real gases deviate when intermolecular forces become significant (high pressure, low temperature) — the van der Waals equation $(P + a/V^2)(V - b) = RT$ corrects for this.