15.3.1—The basic assumptions of the kinetic theory of gases

The ideal-gas kinetic model assumes particles are point-like compared with container volume, move randomly, collide elastically and exert negligible forces except during collisions.

These assumptions explain pressure and temperature while marking the limits of the model for dense or strongly interacting gases.

At lower density, the average spacing increases and intermolecular attractions become less important, so ideal behaviour improves.

“No forces” applies between collisions in the ideal model; collisions still transfer momentum and create pressure.