Assumptions of the kinetic theory of gases
- The kinetic theory of gases is based on the following assumptions:
- Molecules of a gas behave as identical (or all have the same mass)
- Molecules of gas are hard, perfectly elastic spheres
- The molecules are in continuous random motion
- There are no forces of attraction or repulsion between the molecules
- External forces (e.g. gravity) are ignored
- Newton's laws apply
- The volume of the molecules is negligible compared to the volume of the container
- The molecules collide perfectly elastically with the walls of the container exerting a pressure upon them
- The time of a collision is negligible compared to the time between collisions
- There are a very large number of molecules
Gas molecules in a box
Gas molecules move about randomly at high speeds
Examiner Tip
Make sure to memorise all the assumptions for your exams, as it is a common exam question to be asked to recall them.