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enormously rich and logically consistent intellectual framework from within which to characterize macroscopic behavior composed of unknown molecular mechanisms.
Ideas about entropy grew out of William Thomson's (a.k.a Lord Kelvin) thermodynamic laws about energy conservation and its allowable transformations. Later Clausius decomposed the energy into that which was available for mechanical work, called work-content, and that which was not, called transformation content. He referred to the transformation content, a reflection of what changes in the internal order properties of the system that occurred as a concomitant of changes in energy and heat, as the entropy.
Rudolph Clausius added the word entropy as a thermodynamic property to the conceptual armamentarium of theoretical physics in about 1865. This followed the earlier work of the French engineer, Nicolas Leonard Sadi Carnot, who was trying to develop a theoretical framework within which efficiencies in heat-generating engines might be understood. It implicated positive, > 0, changes, d, in entropy, S, with changes in time, t, i.e. dS/dt > 0, entropy is increasing in time, as a concomitant of the inevitable mechanical inefficiencies in an energy driven system. The resulting losses in the form of wasted energy show up as increases in molecular motion, which could be estimated from the increases in heat. Wasted energy dissipated as heat increases the amount of random motion and volume occupied by the surrounding molecules in physical processes involving heat, pressure, vaporization, condensation and work; all elements of that era’s dominant physical metaphor, the steam engine.
The highly developed, multifaceted, often quite abstract formal characteristics of the inferred property, entropy, prevent glib definitions and generalizations. In the context of Kelvin-Clausius theory, the entropy of a closed system will remain the same if it is isolated from any matter or energy exchanges with the environment. If heating a system such that the change, d, in heat, Q, is positive, i.e. dQ > 0, it experiences a rearrangement in its microstructural motions, but the temperature is left unchanged. The (inferred) entropy, S, increases (i.e., dS > 0) as the ratio of change in added heat, dQ, over the unchanging, absolute

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