Postulates of Kinetic Molecular Theory
The kinetic energy associated with the molecules’ velocity: KE = (1/2) mass x u2
The temperature of matter is a measure of its thermal energy, such that T is proportional to the average KE. so that their velocity (u) is proportional to √T.
Gas molecules make collisions with the walls, and on average simply reverse their momentum in the direction perpendicular to the wall. This gives rise to the pressure (force per unit area) on the wall.