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>>Aaaiiieeee! Is this is yet another attempt to re-define "heat"????
No this is not another attempt to re-define heat.
>>I think this is a step in the wrong direction.
So do I, but no such step was taken.
>>As I have said before, there are two issues here; a big issue and a small
>>issue. The definition of the word "heat" and other language details are
>> the_small_ issue. The much larger issue is conceptual.
>>
>>The big conceptual blunder is the over-emphasis on "energy transfer due to
>>a difference in temperature". It's really quite secondary to a modern
>>understanding of thermodynamics. Focusing thereon puts you at a
>> tremendous
>>disadvantage when discussing situations where thermal energy is being
>>_created_ not just transferred:
What is this vague stuff called "thermal energy"? Why not just say internal
energy or just energy?
As far as I have been able to determine there are
only two kinds of (non-relativistic) energy: kinetic (energy of motion) and
potential (energy of position).
Thermodynamic internal energy (internal
energy or energy for short) is the sum of these two kinds.
So why do we need a term "thermal energy"? [1] And how in the name of all
that is holy can anyone "create" thermal energy? [2] I thought that energy
could be neither created nor destroyed. This is what students are told on
day one. [3] Doesn't it seem a bit contradictory, if not confusing, to
then talk about the creation of energy? [4] Since the defining property of
energy is that it is a quantity that is conserved, the only thing that can
happen is that energy of one measurable kind can be transformed into
another kind. [5] Example: I drop a rock onto the floor. Just before the
rock hits the floor it has a certain (mass-motion) kinetic energy, which
can be measured. After the rock hits the floor its mass-motion kinetic
energy is zero. But if we believe that energy is conserved, we also must
believe that the mass-motion kinetic energy has been transformed into
another kind that requires different kinds of instruments (e.g.,
thermometers) to measure. Is it wise to say that "thermal energy" has been
created? [6] I think not given the confusion this is likely to cause
because of the frequently repeated mantra that energy can be neither
created nor destroyed. [7] Why not just say "transformed"? The word
transformation is well suited: it means a change of form.
>>To the modern way of thinking:
>> 0) The zeroth law of thermodynamics states that there is such a thing
>> as thermal equilibrium. In equilibrium, objects have the same
>>temperature. This is true and important.
>> 1) The first law of thermodynamics states that energy is conserved. In
>>particular, energy obeys a _local_ conservation law. This is the first
>>law; nothing more, nothing less. This is true and important.
>> 2) The second law of thermodynamics states that entropy obeys a local
>>law of nondecrease. This is true and important.
>> 3) The third law of thermodynamics alleges that the entropy of some
>>things goes to zero as temperature goes to zero. This is true except when
>>it's not true. It's not very important.
>> 4) Entropy is defined in terms of statistics. It is well defined even
>>when the temperature is unknown, irrelevant, or zero. This is true and
>>important.
>>
>>
>>Note that the word "heat" does not appear in the foregoing laws. Getting
>>the big picture does not require worrying about the exact definition of
>>"heat".
>>Moving now from the large issue to the small issue: Once you have some
>>semblance of a modern understanding of thermodynamics, there is no harm in
>>using "heat" as a noun, in just the way it was used by Rumford in 1798 and
>>is still used by respectable experts today.
You are right,
but students do not have a "semblance of modern understanding
of thermodynamics."
Experts in a field can say the most outrageous and
illogical things because they know better. They can use sloppy metaphors,
ill-chosen figures of speech, without much harm--when they are talking
amongst themselves.
But someone who is learning something for the first time
has no choice but to accept all statements as literal.
Students are not capable of distinguishing between the literal and the
figurative.
As a matter of fact, Rumford did not discredit the caloric theory. The role
of Rumford in thermodynamics has been greatly exaggerated in textbooks,
especially ones written by Americans. I suggest that you read Fox's
historical treatise The Caloric Theory of Gases, in which he states that the
"history of the theory could be written with scarcely any reference to
Rumford."
>>To summarize: My advice is to keep your eye on the ball. Energy is
>>important! Entropy and temperature are important!
I quite agree.
My parting shot is to note the following. In the first law of
thermodynamics work and heat appear symmetrically, as equals.
like it or not energy transfer due to temperature differences is what is
of most relevance to our everyday lives.
It is
impossible to make a measurement on any system to determine how much heat it
contains or how much work it contains. So why don't the folks who insist
that heat is some kind of substance (i.e., a noun) also make the same claims
about work? What is good for the goose (heat) is good for the gander (work).