Introduction: The kinetic molecular theory of gases makes certain assumptions about the sizes of gases, their attractive forces, their collisions, and the relationships between temperature and average kinetic energy. Specifically, the kinetic molecular theory of gases assumes the following: (1) gas particles are infinitely small, (2) intermolecular forces are virtually zero between particles of a gas, (3) the kinetic energy of gas particles is directly proportional to the temperature of the gas particles, and (4) gas particles undergo elastic collisions that allow for the transfer of energy between particles.

In the real world, however, the kinetic molecular theory of gases doesn't necessarily hold. For example, real gases that we see in the world - such as xenon - are not infinitely small, have some kind of attractive or intermolecular forces, and some energy is not transferred between particles. Therefore, the kinetic molecular theory of gases primarily makes assumptions for what are known as ideal gases, which exist at conditions of high temperature and low pressure.