Re: heat, a nonconserved quantity

[Jack Uretsky <jlu@HEP.ANL.GOV>]

Hi all-
        I add to John's remarks.  Heat behaves as a conserved quantity
(to a good approximation) in certain processes.  That is why we can
define such quantities as "latent heat of fusion", or
"latent heat of vaporization", or "heat capacity".
        It is convenient to treat heat as a conserved quantity when
solving the following problem:
        100 gm of ice at -1 deg C is put into an insulated container
containing 20 gm of water at +1 deg C, all at a pressure of 1 atm.
How much ice is left, and what is the temperature of the water when the
system reaches equilibrium?
                                        Regards,
                                                Jack
On Wed, 31 Jan 2001, John Denker wrote:

> At 04:33 PM 1/31/01 -0700, Larry Woolf wrote:
>
> > If heat is a conserved quantity, define heat and the conservation law that
> > it obeys.
>
> Heat is not a conserved quantity.  That's been known for well over a
> hundred years.
>    http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Clausius.html
>
> By way of analogy:  snow is not a conserved quantity, either.  Yet I'm
> reasonably certain that snow exists.  Talking about snow has considerable
> pedagogical and practical utility.  The word "snow" is a noun (as well as a
> verb).
>
>
> > Bohren's point is that almost all situations can be better
> > described by using temperature instead of heat.  Temperature is well
> > defined.  Heat is not.
>
> Some people from time to time say stupid things about heat.  But then
> again, people have been known to say stupid things about snow, and about
> energy and momentum and silicon and hundreds of other things that somehow
> continue to exist.  Just because some people say stupid things about them
> doesn't prevent the rest of us from properly using these nouns and
> benefiting from the ideas they represent.

--
While [Jane] Austen's majestic use of language is surely diminished in its
translation to English, it is hoped that the following translation conveys
at least a sense of her exquisite command of her native tongue.
                        Greg Nagan from "Sense and Sensibility" in
                     <The 5-MINUTE ILIAD and Other Classics>