Introduction to entropy: Difference between revisions

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The concept of [[Entropy (classical thermodynamics)|thermodynamic entropy]] arises from the [[second law of thermodynamics]]. This law of entropy increase quantifies the reduction in the capacity of an isolated compound thermodynamic system to do [[Work (thermodynamics)|thermodynamic work]] on its surroundings, or indicates whether a thermodynamic process may occur. For example, whenever there is a suitable pathway, heat spontaneously flows from a hotter body to a colder one.

Thermodynamic entropy is only measured as a change in entropy (<math>\Delta S</math>) to a system containing a sub-system which undergoes heat transfer to its surroundings (inside the system of interest). It is based on the [[macroscopic]] relationship between [[heat flow]] into the sub-system and the temperature at which it occurs summed over the boundary of that sub-system.

Following the [[Clausius theorem|formalism of Clausius]], the basic calculation can be mathematically stated as:<ref>I. Klotz, R. Rosenberg, ''Chemical Thermodynamics – Basic Concepts and Methods'', 7th ed., Wiley (2008), p. 125</ref>