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Entropy Variation - System, Neighborhood and Universe

  1. Mar 18, 2013 #1
    I learned ΔSuniv = ΔSsys + ΔSneib

    If ΔSuniv > 0 the process is spontaneous.

    But ΔS = Q/T right? Shouldn't Qsys = -Qneib? (The heat released by the system = - heat released by the neighborhood)
    I cannot understand why this is wrong!

    If it were the case, ΔSuniv would be always zero

    Can anyone help me?

  2. jcsd
  3. Mar 18, 2013 #2


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    Science Advisor

    ##\Delta S=Q/T## only for reversible processes.For irreversible processes, ##\Delta S>Q/T##.
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