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Cole A.
Feb5-13, 12:22 PM
P: 12
I'm having trouble understanding the relationship between a system's energy level and its stability (in a general sense).

My understanding is that chemical and physical systems experience a driving force that pushes them toward the lowest possible energy state (ignoring quasi-steady states and those things). Biochemistry calls this the Gibbs energy of reaction when the systems are chemical. The driving force represents the amount of non-PV (or useful) work that might be done by the system in moving toward that lowest energy level, and thus the system does the max amount of non-PV work by moving from an arbitrary energy level to the Gibbs energy minimum, or the energy level characterized by

\frac{dG}{dt} = 0.

But I do not understand why the driving force exists (i.e. why it is favorable thermodynamically for a system to minimize its free energy). In other words, I cannot tell from the the laws of thermodynamics why natural systems tend toward lowest energy states.

And I also do not understand why a stable system corresponds to a low-energy one. My engineering prof. calls the state of lowest energy the state of maximum stability. Stability is a term that is tossed around a lot it seems, but I don't really understand what it means.

P.S. If the best answer would be something along the lines of "take a proper thermodynamics course," that would be fine.

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