In article ,
Ned Simmons wrote:
In article ,
says...

I'm not looking for a demonstration, Ned. A simple explanation would
do. If you find it "impossible" to explain then that's one thing, but
could you at least try? I'm very frustrated with people who simply
assert complex facts without trying to explain them. They do teach
thermodynamics to college freshmen, and I don't usually fail to
understand concepts from freshman physics.
Grant

Unfortunately the demonstration is much easier than the
explanation. I just looked at Resnick and Halliday (my
freshman physics text) and it devotes about 40 pages to a
good quick introduction to thermo.

But that book is pretty pathetic; it drones on and on, not saying things
as accurately and concisely as they should be said. Fermi's book on
thermodynamics is much better (as befits one of the greatest physicists
of the last century): it spends about the same number of pages on a
really good explanation of everything up to and including entropy. It's
not easy reading, but it isn't difficult for stupid reasons; it is as
easy as the subject permits.

Please don't take any of this as a
rigorous presentation, and don't waste time with web sites
that use entropy to prove the existence (or non-existence)
of God. g

Also don't waste time listening to people who try to say that entropy is
a way of measuring the amount of chaos in a system, as opposed to the
amount of order. Entropy doesn't correspond to everyday notions of order
and chaos. What these people say is that increasing entropy means
increased chaos; but if, for instance, you pour one jar of paint into
another, resulting in a chaotic-looking mess of colors, that system has
less entropy than it does after you mix the colors thoroughly, creating a
nice, even, orderly, uniform color.

The first law is the conservation of energy, pretty
straightforward and intuitive to most of us. However, many
processes can be imagined that, although they do not
violate the first law, do not proceed naturally. For
example a hot chunk of metal will not jump up in the air
and drop in temperature to compensate for its increased
potential and kinetic energy.

The second law predicts which processes *will* occur
naturally, and entropy is the property that quantifies the
2nd law. Any process that occurs on its own will move in a
direction such that net entropy increases. Entropy is *not*
conserved, and to my mind, is not at all intutitive.

Entropy can also be thought of as an indicator of how much
of the energy in a system is available to do work. As
entropy rises, energy available for work falls. Relevant to
this thread, the entropy of a gas increases as it expands,
reducing available work.

That's as far as I'm sticking my neck out-hopefully it'll
give you a place to start.

Your neck is safe.


--
Norman Yarvin