PVT surface for a real substance Regions where Van der Waals’ PVT surface is multi-valued is where one finds co-existence of phases.

Phase Diagram of CO2 Critical Point Triple Point

Water: CP at 374 C and 218 atm

dU = TdS – pdV + mdN DSuniv ≥ 0 : equality for reversible process Isolated system tries to maximize S. Interacting system tries to minimize F, G, H.

Thermodynamics is a funny subject Thermodynamics is a funny subject. The first time you go through it, you don't understand it at all. The second time you go through it, you think you understand it, except for one or two small points. The third time you go through it, you know you don't understand it, but by that time you are so used to it, it doesn't bother you any more. Arnold Sommerfeld