The kinetic theory of gases explains the relationship between the pressure, temperature and volume of gases base on the following assumptions:
The gas consists of very small particles, each of which has a mass.
These particles are in constant, random motion.
The rapidly moving particles constantly collide with each other and with the walls of the container. All these collisions are perfectly elastic.
There are forces of attraction between particles of matter. These attraction forces will increase as the distance between the particles becomes closer.
The average kinetic energy of the gas particles depends only on the temperature of the system. The higher the temperature, the higher the kinetic energy of the particles.