Re: question to espinosa

["W. Barlow Newbolt" <wnewbolt@liberty.uc.wlu.edu>]

	Since I set up this straw man, I guess I should reply.  The way I 
am defining internal energy it doesn't change in this example.  "udm" or 
"udn" -- it doesn't matter -- it's all internal energy.  At first it 
is the chemical possibility for a reaction.  In the final state it is 
basically kinetic energy of the molecules of the gasses which have reacted.
I call it thermal energy because I don't know what else to call it.  I'm 
open to suggestions!
	I agree with Joel.
						Barlow Newbolt
On Wed, 18 Sep 1996, Rauber, Joel Phys wrote:

> Espinosa wrote regarding the burning gas in container Gedanken Experiment:
>
> > In a recent note someone gave an example of an explosion in a cylinder
> > that would show that the term "thermal energy" would be useful.  The
> <statement used an adiabatic wall, so dQ = 0, the walls were rigid, so
> <dV = 0 and no work was done, therefore from the first law of thermo-
> <dynamics it followed that dU = 0.  Yet, the inside gas was at a
> <higher temperature, so that was due to thermal energy.  Actually, the
> <expression for the first law of thermodynamics had been written in an
> <incomplete form.  For an explosion to be possible the original gas
> <could not have been a simple substance, it must have been, for example,
> <a mixture of gasoline vapor and oxygen gas.  It was Gibbs who made
> <the great contribution to chemistry by extending thermodynamics to
> <chemical reactions in 1878 with his paper:  "On the equilibrium of
> <heterogenous substances."  The added terms to the first law were in
> <the nature of udm for each substance; it is more customary now to use
> <dn instead of dm.  In conclusion, it is not true that dU = 0 in the
> <example above.  Thermal energy, which sounds like temperature energy,
> <has no place in physics, the energy of a body is its internal energy.
>
> I don't understand a few points and would like them clarified.  For purposes 
> of discussion lets asasume the reaction in the container is A + B -->  C, 
> where A,B,C are the molecular species in question.
>
> If by internal energy, I mean the internal energy of all the stuff inside 
> the container both before and after the reaction; is not Delta U = 0; then. 
>  If  not, what happened to conservation of energy; as this was all occuring 
> in an isolated container.
>
> If you agree with the above paragraph, I think that espinosa's reply applies 
> then to the internal energy of one of the species present; e.g. Delta U(A) 
> ~= 0.
>
> ~= means not equals.
>
> It strikes me then that the original reply to this gedanken experiment is 
> more appropriate; namely that internal energy is more than the random 
> kinetic energy in the system, but also includes potential energy.  So the 
> process converted potential energy to random kinetic energy; which is what 
> it is more closely related to temperature.
>
> Comments, clarifications, or corrections to my misunderstandings are 
> appreciated.
>
> Joel Rauber
> rauberj@mg.sdstate.edu