A phase transition from solid to liquid takes place at constant
pressure and temperature. This is a closed PVT system. (a) Show
that the Gibbs free energy G = U - TS + PV is a constant. (b) The
solid and liquid phases are in equilibrium at a temperature T and
pressure P, where G(solid) = G(solid)(T,P) and G(liquid) =
G(liquid)(T,P). The phases are also in equilibrium at the
neighboring temperature T +dT and pressure P + dP, where G(solid)...