For 10 points, name this measurement of disorder in a system.
For an isothermal process, the change in this quantity is equal to nR (en are) times the natural log of the ratio of volumes. Heat capacity is equal to temperature times the partial derivative of this quantity with respect to temperature.  This quantity can be calculated by finding the natural logs of available microstates, and its change is equal to the change in heat divided by temperature.  It can be defined as the amount of thermal energy in a system that cannot do useful work, and the second law of thermodynamics means that for the universe this is always increasing. For 10 points, name this measurement of disorder in a system.
For an isothermal process, the change in this quantity is equal to nR (en are) times the natural log of the ratio of volumes.
entropy