2. Real fluids

The perfect gas, whose properties are described in the previous paragraph, is a highly simplified model of the gaseous state since, in practice, only gases under low pressure can be considered perfect. It therefore seems obvious that the equation of state for perfect gases is incapable of correctly calculating the PVT properties of matter, particularly in high-pressure states, whether gaseous or liquid.

On the other hand, from a theoretical point of view, the molecules of a perfect gas should be almost point-like with no interaction. However, there are two main causes of imperfection in molecular edifices, namely the molecules' own volume and molecular attractions. In fact, when two molecules are far enough apart, they attract each other (London forces). When they are very close, they repel each other (Pauli forces), which prevents them from superimposing and enables...