Re: Energy, etc

[Jim Green <JMGreen@SISNA.COM>]

>         Ok, I'll jump in too.  Didn't this list spend a lot of time
> railing against the word 'heat' being used as a noun??  Weren't we all in
> agreement that 'heat' means 'energy transfer'?  But, if energy cannot
> 'flow' (a word I actually dislike; too caloric sounding), what do we do
> with the dQ in dU=dQ-dW ?

I have assiduously stayed far from the word "heat", but feel now that I
must rush to its aid:

HEAT IS NOT ENERGY!!!  NOR DOES IT FLOW!!!

Sorry to shout, but it would be nice to get at least this straight in our
minds.  U is not "energy" either really (energy is not a substance); U is
the energy level of the system!!!  W and Q are ACTIONS  DONE TO the
system.  Neither heat nor work "flow" -- nor does energy!!!  Energy is a
property of the system and can be changed by actions on the system.

I reluctantly agree to the word "transfer" -- although I think that it is
terrible pedagogy -- as long as the message is given that "transfer" is
like a bank transfer of funds -- the account balance is so much here and
after the transfer the account balance here is changed and the account
balance there is changed, but no dollar bills move from here to there.

No analogy is perfect and this one may not be all that great, but it is the
best I can do.

The energy is a property of  a system:  the level of energy of a system (or
part of a system) can increase or decrease.  This is done by a mechanical
mechanism called work -- heating is one form of such work.  But neither
energy nor heat nor work flow -- (neither do blue nor charge nor mass).  If
we teachers would begin to use proper terminology, our students would begin
to understand the First Law -- and we could make sense to each other (:-)

There that is off my chest.  I feel so much better now.

Now if we launch into another argument re the four letter word "heat", I
think that I will not participate (write me privately if you wish, but
visit my web page re the First Law first)  For any ensuing "heat"
discussion it is Leigh's turn; he was taking a sabbatical from the list
during the last "heat" episode.  Also, it would be nice if those timid
souls who have said to me "Ah, now I understand" would speak up here.

Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen