A few days ago, Chuck Britton wrote "And once again, this list will be
drawn into the HEAT of battle!" and so It has proved to be.
There is a difference of opinion among those on the list and there are
some who hold very strong views.
John Denker is the high priest of those who believe that the word heat
can be used in many ways and that the context will allow whoever wants
to understand you to understand you.
I can see quite well where John is coming from; the community of
practitioners who know their way around, those who move easily among
ambiguities, who have overcome their initial uncertainties about the
subject and its word usage, in fact, as John writes, who "communicate
the details using equations".
Those of us who have struggled with aiding student understanding of
the, to them, new concepts involved (and overcoming the so common
heat-temperature misconception) fall into the opposing camp in this
discussion. We are very interested in restricting the use of the word
"heat". We want "heat" to be associated with energy transfer.
BTW there is some disagreement within this camp regarding the use of
the term energy flow (or heat flow) but that is not a path I want to
run down at the moment.
John refers to this specialised use of the word "heat" as "Using the
word in new ways" and believes such use "is an impediment to
communication." But the restriction of "heat" to energy transfer due
to difference in temperature across the boundary of a system is far
from new. It is not a recent fad arising from the work of we pesky
PER folk. Zemansky's text, Heat and Thermodynamics, described by
Herbert Callen as "the classical introductory text in English" was
first published in 1951, half a century ago. Some time late, Zemansky
was awarded one of the prize medals for his work in promoting the
teaching of thermodynamics and in his acceptance address was scathing
of those who did not restrict the use of the term heat to energy
transfer. Perhaps someone can lay hands on the AJP reference.
Arnold Arons in his excellent text deals with this topic in detail
(pages 139 onwards) .He writes "for the sake of clarity and precision
in forming and using the energy concepts in subsequent study, it is
advisable never to speak of the "heat in a body" even in the early
stages of development of the concept. The term should be used only in
connection with the process of transfer into or out of a body or
system. This is the usage in thermodynamics."
In John's posting, he uses an analogy involving water and rain. This
reminded me of a much stronger and well developed analogy used by
Callen in his important text "Thermodynamics" (Callen forsakes the
conventual inductive development of thermodynamics in favour of a
postulational approach but it is the same physics put together in an
elegant fashion - the basis for a second course for the junior or
senior student). Callen's analogy (page 19) starts " A certain
gentleman owns a little pond, fed by one stream and drained by
another. The pond also receives water from an occasional rainfall and
loses it by evaporation, which we will consider as "negative rain".
In the analogy we wish to pursue the pond is our system, the water
within it is the internal energy, water transferred by the streams is
work, and water transferred as rain is heat." Callen develops the
analogy for the best part of a page -the first point is that no
examination of the pond at any time can indicate how much of the water
came from the streams and how much by rain. I won't quote any further
here; if anyone wants the full development and can't get hold of the
book, I'll run the rest off for them off-list.
So that's where I and, I think, many of us stand. For clarity and
precision and for enhanced student understanding we certainly do want
to restrict the use of the word - as the majority of texts over the
last 50 years have.