Handbook of Thermodynamics[Softcrate]

Thermodynamics is the science of energy conversion involving heat and other forms of energy, most notably mechanical work. It studies and interrelates the macroscopic variables, such as temperature, volume and pressure, which describe physical, thermodynamic systems. Thermodynamics concerns phenomena that are experimentally reproducible. For example, a state of thermodynamic equilibrium is a steady state reached after a system has aged so that it no longer changes with the passage of time. But more than that, for thermodynamics, a system, defined by its being prepared in a certain way must, on every particular occasion of preparation, upon aging, reach one and the same eventual state of thermodynamic equilibrium, entirely determined by the way of preparation.

The meanings of the terms used in this statement are clarified in the following, but experimental reproducibility is a primary and fundamental requirement for thermodynamics. This is the source of the strengths and the weaknesses of thermodynamics. Thermodynamics does not deal with phenomena that are not experimentally reproducible.