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  2. Spontaneous process - Wikipedia

    en.wikipedia.org/wiki/Spontaneous_process

    When ΔS > 0 and ΔH < 0, the process is always spontaneous as written. When ΔS < 0 and ΔH > 0, the process is never spontaneous, but the reverse process is always spontaneous. When ΔS > 0 and ΔH > 0, the process will be spontaneous at high temperatures and non-spontaneous at low temperatures. When ΔS < 0 and ΔH < 0, the process will be ...

  3. Thermodynamic free energy - Wikipedia

    en.wikipedia.org/wiki/Thermodynamic_free_energy

    For a process at constant temperature and pressure without non-PV work, this inequality transforms into <. Similarly, for a process at constant temperature and volume, <. Thus, a negative value of the change in free energy is a necessary condition for a process to be spontaneous; this is the most useful form of the second law of thermodynamics ...

  4. File:Scheme of spontaneous parametric down-conversion.pdf

    en.wikipedia.org/wiki/File:Scheme_of_spontaneous...

    You are free: to share – to copy, distribute and transmit the work; to remix – to adapt the work; Under the following conditions: attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made.

  5. Second law of thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Second_law_of_thermodynamics

    or dG < 0. For a similar process at constant temperature and volume, the change in Helmholtz free energy must be negative, <. Thus, a negative value of the change in free energy (G or A) is a necessary condition for a process to be spontaneous. This is the most useful form of the second law of thermodynamics in chemistry, where free-energy ...

  6. Entropy (statistical thermodynamics) - Wikipedia

    en.wikipedia.org/wiki/Entropy_(statistical...

    Many systems, such as crystal lattices, have a unique ground state, and (since ln(1) = 0) this means that they have zero entropy at absolute zero. Other systems have more than one state with the same, lowest energy, and have a non-vanishing "zero-point entropy".

  7. Helmholtz free energy - Wikipedia

    en.wikipedia.org/wiki/Helmholtz_free_energy

    and thus for a system kept at constant temperature and volume and not capable of performing electrical or other non-PV work, the total free energy during a spontaneous change can only decrease. This result seems to contradict the equation dF = −S dT − P dV, as keeping T and V constant seems to imply dF = 0, and hence F = constant.

  8. Introduction to entropy - Wikipedia

    en.wikipedia.org/wiki/Introduction_to_entropy

    Download as PDF; Printable version; ... This can be either 0, 1, or 2. We can call these "macrostates". ... Spontaneous thermodynamic processes are irreversible, in ...

  9. Entropy (classical thermodynamics) - Wikipedia

    en.wikipedia.org/wiki/Entropy_(classical...

    If we calculate the entropy S 1 before and S 2 after such an internal process the Second Law of Thermodynamics demands that S 2 ≥ S 1 where the equality sign holds if the process is reversible. The difference S i = S 2 − S 1 is the entropy production due to the irreversible process. The Second law demands that the entropy of an isolated ...