For 10 points, name this quantity that is a measure of the disorder of a system.
The cross of the velocity and vorticity vector plus the temperature times this quantity equals zero according to Crocco's theorem. The mass density multiplied by the time derivative of the "specific" form of this quantity is greater than the negative divergence of heat flux over temperature, plus mass density times heat source per unit mass over temperature, according to the Clausius-Duhem inequality. Because Liouville's theorem requires flows in phase space to evolve incompressibly, one obtains a (*) counterintuitive result when considering this quantity as the logarithm of a volume in phase space. The heat transferred is equal to the area under the curve of a process when it is plotted on a diagram of temperature versus this quantity. A process with constant value for this quantity is adiabatic and reversible. For 10 points, name this quantity that is a measure of the disorder of a system.
The cross of the velocity and vorticity vector plus the temperature times this quantity equals zero according to Crocco's theorem.
entropy [or: delta S]