Re: Definition of heat [and S]

[Ludwik Kowalski <KowalskiL@MAIL.MONTCLAIR.EDU>]

Referring to:

> > There are more important issues to deal with; some students
> > are not aware of the fundamental difference between heat and
> > temperature.

Jim Green wrote:

> Some _instructors_ are not aware of the difference!!!  That is
> why we have the annual discussion -- but it might appear that
> we are back in the 80s when this discussion began.

I do not think this is true, at least on this list. We are constantly
returning to some topics because:

1) they have deep content
2) they are fascinating
3) we face them each year
4) terminology is often ambiguous
5) we do not time to analyze all messages
6) we forget what we learn
7) new phys-L-ers ask old questions
8) we evolve and see things differently
9) physics is fun

> > Heat is a form of energy.
>
> "Heat" (if by "heat" one is referring to Q) is not in any way a form of
> "energy".  "Heat", ie Q, is an action that might be _done_ to a
> system,  Just as "work" is something that might be _done_ to a system.

10 joules of that action, Q, represents a contribution to the internal energy
change of a system. Some call it heat, others call it thermal energy and you
are calling it action. But we all agree that the internal energy (of a defined

system) changed by 10 joules due to that contribution. Some say that the
10 joules flow, others say it is received or accepted or injected or supplied.

But we all agree it was not there before and it is there now. It can not be
distinguished from other "actions" (including work) or from what were
there to begin with.

> Saying "heat is lost" reifies  [Leigh's favorite word] the concept of
> "heat" and is not a valid.

In a recent message Leigh emphasized that the role of a physics teacher
is to associate correct ideas with common words, when they are used to
identify physical quantities. We can not prevent students from using the
word heat but we can help them to associate that word with energy of
random motion of molecules and atoms. And we can tell them that in
calorimetry we still use the old caloric model of "heat is a weightless
substance". Then we proceed and explain limitations of that model.
I am glad that you recognized this, Jim.

> The "caloric" analogy is _always_ "totally wrong".  It may be useful as
> short hand, IF in the lecture/discussion it is made patently clear that
> this anachronistic analogy is being used.  (Note btw that Carnot had
> suspicions that the prevailing concepts were wrong, but he had other things
> on his mind and did not investigate it further.  And Rutherford was simply
> ignored.  He still is to a large extent.)

You meant to say Rumford, I suppose. Why do you say he is still ignored?

Regards, Ludwik.