Entropy and the 2nd law of thermodynamics. We start with a review of the 1st law of thermodynamics. Then we find another exact differential related to heat. Earlier we introdudced the enthalpy and now we arrive at entropy. Then, with the fact that heat flows from hot to cold we show that the entropy must increase for the classic example where a fixed volume of gas is surrounded by a heat reservoir. We analyze the entropy change in detail for the cases where the iniWe briefly discuss the Clausius and Kelvin-Planck statements of the 2nd law.
