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Chemomechanics t1_jd4pbix wrote

Reply to comment by LoyalSol in Can a single atom be determined to be in any particular phase of matter? by Zalack

> One bit of nitpick. Entropy is still very well defined even at the atomic level. There's many different types of entropy, but they all are related to the same underlying concept.

Isn't it clear from the context that I'm referring to the thermodynamic entropy as applied to ensembles of molecules to determine the equilibrium bulk state?

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LoyalSol t1_jd4w78f wrote

Yes, but even that is still one to one correspondence with the partition function which is the number of accessible states.

The thermodynamic entropy is actually defined well at the atomic level. Where as many other properties only exist in the bulk limit.

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Chemomechanics t1_jd5cot7 wrote

Sorry, I don’t see how this helps the OP. It sounds like you’re talking about looking at the behavior and any transitions over a very long time rather than relying on the ergodic hypothesis and stat mech assumptions based on large N. OK, so now you’ve calculated what you consider the entropy. I don’t get how this allows the OP to classify the atom as a bulk solid, liquid, or gas when it’s a lone aqueous atom.

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LoyalSol t1_jd5zils wrote

I made the point about time to show how you can prove the entropy exists in the absence of large N. It is not exclusive to that however.

I was not making a point about the OP question as much as clearing up a statement that entropy is a strictly bulk property when it isn't. Unlike many thermodynamic definitions entropy is actually defined the same way on both a macro and micro scale.

Thus why I called it a nitpick.

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