So at very high pressures the distance between any two molecules is approximately the same as the size of the molecule itself. Now, and I claim under this condition the kinetic theory breaks down. So let's see, what about the kinetic theory that breaks down in this system? Well, now, the molecules are very close to each other. They're so close, in fact, that they will attract each other and repel each other. So the forces that we spoke about before that we neglected.