1. Gases are made up of particles that are in continuous motion, colliding with each other and with the walls of the container.
2. There are no attractive or repulsive forces between the molecules of a gas.
3. The volume of the gas molecules is negligible compared with the spaces between them.
4. When molecules collide, the collisions are perfectly elastic.
5. The average kinetic energy of the molecules is proportional to the temperature in Kelvin scale.