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Re: [Phys-L] Figuring Physics solution Jan 2018

I doubt if mentioning "Gibbs free enthalpy space" would be enlightening to anyone in Hewitt's intended audience.

My PhD is in Atmospheric Physics. While in graduate school, I sat in on many classes where professors who were almost household names in meteorology would awkwardly fumble their explanation of what is happening when water boils. It is definitely NOT 5th grade physics. Mentioning Gibbs free enthalpy is very much like trying to explain to a lay person why a moving wing produces lift - mentioning circulation is less than useful.

Bob formerly at PC

From: Phys-l <> on behalf of John Denker via Phys-l <>
Sent: Thursday, January 25, 2018 5:49 AM
Cc: John Denker
Subject: Re: [Phys-L] Figuring Physics solution Jan 2018

Question: If you put a pot of water on the stove to boil,
is this a warming process or a cooling process?

Answer: Neither of the above. Under ordinary conditions,
water boils at constant temperature. It could be described
as an endothermic process. By any reasonable definition,
warming and cooling refer to change in temperature, so
neither is a good description of the process.

Note: This is fifth-grade physics.

Note: Chemists (for good reasons) and biologists (for even
better reasons) tend to assume, unless otherwise stated,
that everything is held at constant temperature, even when
there is not a phase-change involved. Processes roll
downhill in Gibbs free enthalpy space (not in energy
space). This is yet another reason why asking whether
something is a warming process or cooling process is a
Bad Idea.

Hewitt's question (to some extent) and his answer (to an
much greater extent) trample on the distinction between
energy and temperature.

And that's even if we ignore the counterfactual premise
about speed-independence!

It's an interesting example of how to inflict multiple
misconceptions in a single sentence.

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