All of these calculations, of course, rest on an important assumption: gases behave "ideally". Just what is "ideal" behavior?
The four "big ideas" of kinetic theory more or less describe ideal gas behavior. As we mentioned before, this model is only a convenient approximation of how gases behave under ordinary conditions. In fact, there are no ideal gases. There are only real gases which behave more or less ideally under different conditions.
The greatest deviations from ideal behavior in a gas are tied to two of the assumptions of kinetic theory:
- gas particles are point masses with negligible individual volume
- gas particles exert no attractive or repulsive forces on one another