Kinetic Molecular Theory

Gases

are composed of molecules that are in continuous motion, travelling in straight lines and changing direction only when they collide with other molecules or with the walls of a container.

The molecules composing the gas are negligibly

small compared to the distances between them.

The pressure exerted by a gas in a container results from

collisions between the gas molecules and the container walls.

Gas molecules exert no attractive or repulsive forces

on each other or the container walls; therefore, their collisions are elastic (do not involve a loss of energy).

The average kinetic energy of the gas molecules

is proportional to the kelvin temperature of the gas.