# what is entropy?

Discussion in 'Mechanical | Automobile | Aeronautics' started by ESSA, Jun 25, 2012.

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## i want know about entropy

Poll closed Jan 25, 2013.
 concept d concept 2 vote(s) 66.7% 3 vote(s) 100.0%

### ESSACertified CEan

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I am a mechanical engineer and I want someone among you to explain me the term entropy and relate it to enthalpy. Why and how is it used? I want to know it in detail. Please explain.

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Engineering Discipline:
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In simple Entropy is a thermodynamic property of a system which increases with addition of heat and decreases with removal of heat.

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enthalpy = internal energy + flowwork
enthalpy and entropy are two different properties of system.

### A.V.RamaniMentor

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Different types of energy have different levels of availability. Even in one kind of energy, say heat, the level of temperature decides the availability of that heat for usable work.
Entropy is a quantitative expression of the degree of unavailability of energy. Greater the unavailability greater the entropy.
Generally all natural (spontaneous) processes are more or less irreversible. Entropy is a measure of this irreversibility. For example water flows down hill by itself. You need a pump to push it back up. By losing potential energy in flowing down water increases its entropy.
Heat flows from a higher to a lower temperature by itself, not the other way One needs a heat pump (such as refrigerator) to push heat the other way.
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### The myth busterApprentice

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