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Re: energy in the tank



How about higher, available for biological use, energy ATP?

this would prompt student questions answered by e.g. gasoline has more PE, but
is not available for cell use, etc.

bc



Jon Greenberg wrote:

John, thanks for your encouragement.

Jim, I have no problem rewording that statement to something like "much of
the chemical potential energy of the reactants (or heat of combustion, or
whatever you prefer) becomes kinetic energy (or thermal energy) that drives
PV work."

I have only two questions for you:

1) How would you word that phrase?

2) Aside from that point, are we basically in agreement about the energetics
of these reactions?

As a former biology teacher, I'll freely admit that we are probably the main
culprits in this story. ("High energy ATP" and all that). The mixed-up story
of reaction thermo presented in most bio classes is conceptually appealing
to the chemically naive because it makes intuitive sense and is simpler than
the story we've been discussing here. Unfortunately, it happens to be wrong.

Jon Greenberg

----------
From: Jim Green
Reply To: phys-l@lists.nau.edu: Forum for Physics Educators
Sent: Wednesday, February 6, 2002 11:55 AM
To: PHYS-L@lists.nau.edu
Subject: Re: energy in the tank

Much of the energy released drives the PV
work of moving the pistons.

OK. How's that?

As I have predicted on occasion, when we think of "energy" as a
fluid
substance our conceptualization gets foggy. The energy of a system can
be increased or decreased by doing _work_ on the system, but it is not
"released" or "transferred". One can of course use this faulty shorthand
language in a pinch, but then one runs into the risk of faulty
understanding -- as has been amply demonstrated in this thread.

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