Heat, Temperature and the First Law of Thermodynamics

Thermodynamics developed before the atomic nature of of matter was understood. Major developments occurred in the first half of the nineteenth century. The names Carnot, Clausius, W. Thompson (Kelvin) are major names associated with these developments. Tsallis is a notable current worker in this field. Thermodynamics is based on a small number of basic principles (the laws of thermodynamics.) These are deductions from and generalizations of a large number of the results of a large number of experiments on macroscopic systems. They are phenomological descriptions and are not based on microscopic structure at all. Thermodynamics uses exclusively macroscopic variables such as p, V, and T. Equations of state such as pV = NkT = nRT are experimentally derived.