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    Entropy is a measure of the number of specific ways in which a system can be arranged. It is considered to be the measure of disorder. In an isolated system, entropy never decreases because isolated systems spontaneously evolve towards thermodynamic equilibrium which is the state of maximum entropy.

    Entropy is a thermodynamic quantity that helps to account for the flow of energy through a thermodynamic process. Originally, entropy was defined by a thermodynamically reversible process as

    ΔS = ∫(dQrev)/T

    where entropy is found from the uniform thermodynamic temperature of a closed system divided into an incremental reversible transfer of heat into that system.

    Entropy in thermodynamics is a non-conserved state function that has major importance in the science of physics and chemistry. The concept of entropy evolved in order to explain why some processes occur spontaneously while their time reversals do not. Systems tend to process in the direction of increasing entropy. Chemical reactions cause changes in entropy and entropy plays an important role in determining which direction a chemical reaction spontaneously proceeds.

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    Entropy change of the universe

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    Entropy Change in Melting of Ice: Example Problem

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    Entropy increase of Carnot engine operating on methane

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    Carnot Cycle Efficiency in an Idea Gas

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    Calculating entropy of water, reservoirs, and universe

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    Change in entropy that the Universe has to suffer from Ice Cream melting?

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    change in entropy of the ice/water

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    Microscopic Interpretation of Entropy

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