At high temperature and low pressure, the vanderwaal equation is reduced to ideal gas equation.

i.e, [P + \(\frac{a}{v^2}\)] [v - b] = RT is reduced to PV = nRT

Generally, a gas behaves more like an ideal gas at higher temperature and lower pressure as the potential energy due to intermolecular forces, it becomes less significant compared with the particles kinetic energy and the size of the molecules, then it becomes less significant compared to the empty space between them.