Kinetic theory of gases is the simplest conceivable model to explain behavior of gases in the ideal limit.
It has the following postulates
(i) Molecules are in incessant random motion colliding against one another and with the walls of the container.
(ii) The dimension of a molecule is negligible compared to the average distance between them
(iii) Molecules are perfectly rigid spheres with no internal structure. There are no forces of attraction or repulsion between them, except for contact interaction. Therefore, energy is purely kinetic.
(iv) All collisions of molecules with each other and with walls are elastic. Between two collisions, a molecule moves in a straight line with uniform velocity. The time during which a collision lasts is negligible compared to the time of the free path between collisions.
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