Re: HEAT1=HEAT2 ?

["Richard W. Tarara" <rtarara@saintmarys.edu>]

I would certainly vote for leaving the usage of 'heat' alone in the
introductory texts.  If there really is a concensus, then perhaps some
pressure could be placed on the writers/editors of 'University Physics'
texts for more 'precise' use, but leave the 'College Physics' and high
school texts alone.  It seems to me that to limit the usage of 'heat' to
the classical thermodynamics meaning would only obfuscate the topic for
non-majors.  For these beginning students, we need to work from their
experiences and their vocabulary and the common treatments in introductory
texts tend to do this.

As far as changing the word in thermodynamics,  if we think physics majors
are too dumb to understand that 'heat' has a much more restrictive meaning
in this context, then we could change it.

Rick
----------
> From: LUDWIK KOWALSKI <kowalskil@alpha.montclair.edu>

> Yes, the word heat has two conflicting meanings in many introductory
physics 
> textbooks. In thermodynamics it refers to that part of a thermal energy
change
> which is due to a difference of temperatures, dT, between the inside and 
> outside of a system. It is a path-dependent quantity, usually expressed
in 
> joules. In elementary physics on the other hand, heat is the name given
to 
> the quantity Q when the formula Q=c*m*dT is used to perform simple 
> calorimetric calculations. Students often say that the temperature of a
body 
> is determined by the amount of heat "it contains". Phrases such as "heat
added 
> to a body" or "heat removed from it" are commonly used by teachers who
take
> it for granted that "heat" is a synonym for "thermal energy of molecules
and 
> atoms". The experiments of Joule are often interpreted by saying that 
> "energy in the form of heat" and "mechanical  energy" are equivalent. In 
> thermodynamics, on the other hand, we emphasize that heat is not a state 
> function, such as energy or enthalpy. 
>
> Thus a common statement: "heat is a form of energy" is false in
thermodynamics.
> This situation was created because the same name, "heat", was given to 
> different physical quantities expressed in joules. We use it in
calorimetry 
> and we use it in the first law, dE=Q+W. The recognition of this fact is
an 
> important first step toward the elimination of many conceptual conflicts.
We 
> must then decide what to do about this unfortunate situation. Should the
term 
> "heat" be eliminated from elementary calorimetry and replaced by
"internal 
> energy"? I suspect that most phys-L-ers would favor this "modern"
approach. 
> They would disagree with the following formulation, found in Sears and 
> Zemansky. "The process of combustion releases the internal energy and
converts 
> it into heat. In this form the energy can be utilized for ..."
>
> The other alternative is to retain the traditional meaning of heat (form
of 
> energy) and to invent a new name, for example, "thermal pseudo-energy",
for 
> the path-dependent quantity Q in thermodynamics. This approach could be 
> defended by observing that "heat" is a common word; introductory courses
have 
> traditionally been structured to quantify common words, such as force,
work 
> and heat. Phrases, such as "energy in the form of heat", "heat released
in a 
> reaction", "heat produced through friction" or "heat flows" are too
deeply 
> rooted to be abandoned. Renaming Q in thermodynamics would be less
confusing 
> than renaming it in elementary physics. Wouldn't you agree with Jim that
the 
> most effective way of confusing students and teachers is to redefine 
> traditional words with which they are already familiar. Can students
learn 
> thermodynamics before they learn calorimetry?
>
> By the way, I still think that a distinction between thermal energy and 
> internal energy can be very useful in many problems. Thermal energy is
that 
> part of internal energy which is associated with motions and interactions
of 
> molecules and atoms. The internal energy, on the other hand, is not
limited 
> to its thermal component; part of it may be associated with motions and 
> interactions of macroscopic components of a system, such as wheels,
belts, 
> springs and pistons. The internal energy does not change when friction
slows 
> down a brick sliding along a horizontal surface. But a conversion of
kinetic 
> energy into thermal energy does take place in the system.
>                                                            Ludwik
Kowalski