  Thermodynamics of power means applies to an ideal quantum gas which may be
nonextensive. Transition to an ideal classical gas occurs when the empirical
temperature exponents of the internal energy and absolute temperature coalesce.
Limiting processes are pure heat conduction and pure deformations. Largest and
smallest mean final volumes occur for isothermal and adiabatic processes,
respectively. The increment in the heat admits two integrating factors which
yield conserved quantities for adiabatic processes. Energy-conserving
equilibrations yield the largest final means possible, while the second law
follows from the property that the power means are monotonically increasing
functions of their order. In the ideal classical gas limit, the change in the
average entropy is proportional to the difference between the Shannon and
R\'enyi entropies for nonextensive, isothermal systems that are multifractal in
nature.
