ABSTRACT
Mechanics is inadequate for thermodynamics processes because it does not account for the internal energy stored within macroscopic objects. An appreciation of the strong linkage between internal energy and entropy can bring a deeper understanding of thermodynamics. All thermodynamics processes entail redistributions, i.e., spreading of energy. An example is the mixing of two distinguishable gases, where each species spreads its energy to a larger spatial volume. Analysis of the ubiquitous photon gas shows that not all equations of state are the familiar ideal gas ones. The photon gas is used to highlight a variety of process types. Thermodynamics is typically presented by discussing heat processes and Carnot cycles to get from energy to entropy. Along with attempts to challenge the sacrosanct nature of the second law, are investigations of whether the second law of thermodynamics is fundamentally quantum mechanical. The many successes of quantum theory make this prospect alluring.
