Introduction to entropy: Difference between revisions

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===Thermodynamic entropy===

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 aan isolated compound thermodynamic system forto changedo [[Work (thermodynamics)|thermodynamic work]] on its surroundings, or determinesindicates whether a thermodynamic process may occur. For example, heatwhenever alwaysthere flows fromis a regionsuitable ofpathway, higherheat temperaturespontaneously toflows onefrom witha lowerhotter temperaturebody untilto temperaturea becomescolder uniformone.

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.