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[Phys-l] statistical thermo terminology



Hi --

I'm looking for suggestions on how to resolve some terminology
problems that arise when trying to explain thermodynamics.
(Note that the only way I know to understand thermo is in terms
of statistical mechanics.)

Many of the terms in thermodynamics are horribly ambiguous.
This is an impediment to communication even between experts,
and is even more of a problem for students.

By way of background, some of these problems are relatively
easy to fix. For example, "adiabatic" can have three different
meanings, but this problem can be solved by avoiding the word
entirely:
# If you mean thermally insulated, say thermally insulated.
# If you mean a non-sudden perturbation, say non-sudden or gentle.
# If you mean isentropic, say isentropic.
http://www.av8n.com/physics/thermo-laws.htm#sec-adiabatic

Similarly "heat" and "work" are ambiguous, but there are ways
around that, too.

Now we come to the point of this note: I'm stuck when it comes
to "state" and "phase".
-- State can either mean microstate or macrostate. State always
means microstate in the context of quantum mechanics. Meanwhile,
state always means macrostate in the context of classical thermo,
for instance in the expression "function of state". These usages
are well established, but they collide and conflict as soon as
you start doing stat mech.

An obvious candidate solution is to consistently use "macrostate"
and/or "microstate" instead of "state". However, this gets ugly,
especially in hyphenated forms such as macrostate-function or
microstate-space.

So, can anybody suggest a better solution?

This seems worth worrying about, because in one of my documents,
words related to "state" appear almost as many times as "entropy"
and "energy".

-- Similarly, "phase space" is ambiguous. It means one thing in
classical canonical mechanics, and anotherthing in classical
thermodynamics. (Ironically, Gibbs has his name associated with
both of them.)

Also BTW, I'm not even talking about quantum mechanical phase,
as in exp(i phase); that's a third thing, which is not terribly
troublesome because you can usually figure out the meaning based
on context.

Do we have to write microphase-space and microphase-space? Ick.

I knew it was going to be a bad hair day when I wrote the phrase
"probability spread in state-space", realized it was ambiguous, crossed
it out and replaced it with "probability spread in phase-space", and
realized that was ambiguous, too.

Given how messed-up our language is, it's a miracle anybody ever
communicates anything.