an equation of state relating the pressure, volume, and absolute temperature of a gas, taking into account the finite size of the molecules and the attractive force between them.

Origin of van der Waals' equation

named after J. D. van der Waals (1837–1923), Dutch scientist

An equation that relates the pressure, volume, and absolute temperature of a gas taking into account the finite size of molecules, and their intermolecular attraction, having the form RT = (P + av-2)(v - b), where R is the gas constant, T is the absolute temperature, P is the pressure, v is the volume of fluid per molecule, a is a measure of the attraction of the molecules for each other (due to van der Waals forces), and b is the volume occupied by a single molecule. The equation accurately captures phase transitions between liquid and gas phases of substances. See also ideal gas law.