From: henley@eng.auburn.edu (James Paul Henley)
Subject: Re: Thermodynamics FAQ
Organization: Auburn University Engineering
Date: Fri, 24 Jul 1992 15:17:07 GMT

In article <schinder.711942290@leprss.gsfc.nasa.gov> schinder@leprss.gsfc.nasa.gov writes:
>
>Foolish mysticism, completely unlike "the uncertainty principle".
>Energy is definitely measurable.  (*Define* the term "pure energy").

I didn't say energy wasn't measurable,  I said that you have to use matter
to measure it.

>High energy experimentalists spend their lives measuring it.  There's
>no real distinction between matter and energy; one can be converted
>into the other.

OK, I'll bite, how do you measure pure energy apart from matter without
allowing it to interact with matter?
Give me the measurement technique, and a reference, if you please.

>However, you're neglecting the incoming vs. outgoing radiation.  In
>this respect, the earth is *not* (and can't be so long as the sun
>shines and the earth radiates) a closed system.  In any sense.  No
>doubt (for obvious reasons) you want to try to ignore this "energy",
>but that's too bad.  Thermodyanics has no problems with it.

You are confusing closed systems with isolated systems.  You didn't read
the FAQ.  The definition of a closed system is a system that does not have
mass transfer across system boundaries.  Maybe it is because of the balloon
model?  The wall of the kind of balloon I have in mind does allow a lot of
radiation to enter the balloon.  They reflect some of it too.  In fact they
are selective in which radiation they allow to enter, and which they reflect.
I'll be generous and say that maybe you thought I meant one of those foil
balloons.  They definitely reflect a large amount of radiation.  In that 
case it would *not* be a good model.  I'm talking about the old fashioned
toy kind made out of latex.  (or synthetic latex)

Are you are trying to say that the earth is not a closed system because some
sunlight gets converted into matter, thus increasing the mass of the earth?
You have to show that this conversion of energy to mass is significant
in an overall energy balance.  I made the assumption that it was
negligible.  I would guess that the rate of energy conversion to matter is
*many* orders of magnitude less than the rate of energy conversion to chemical
energy in photosynthesis.  So, let's see, you take CO2, H2O and N2, make sugar,
do a mass balance to determine the additional mass due to the conversion
from energy, and see what number you come up with.  Unless you have a
very precise computer, and some extraordinary means of measuring mass,
you will come up with 0.  So, since it is not measureable, it is not
significant in the overall energy balance.  That does not mean it does not
exist - it is just negligible.

>
>>Two different forms of the Laws of Thermo are used for open and for closed
>>systems.   One consideration in an open system is the fact that energy
>>can be transferred across the system boundaries due to intrinsic energy
>>of the mass that is transferred.
>
>Energy can be transfered in other ways than mass flow.
>

Did you even read the FAQ?  In the FAQ, I mentioned energy transfer by
electrical work, mechanical work, chemical work, radiation, convection,
and conduction.  You are confused about what a closed system is.

>>--------------------------------------------------------------------------
>>o Does Snowflake formation violate the Second Law of Thermodynamics?
>
>>A forming snowflake is an open system.  There is mass transfer across the
>>boundary.  If snowflake formation causes a reduction in the entropy
>>of the snowflake, then, by the second law, the entropy change of the
>>surroundings must increase.
>
>There's also the latent heat released to the environment as the ice
>crystalizes (energy released as the molecules bond).

And if you read the FAQ, you would see that I said that there is an
entropy transfer in the direction of heat transfer.  In this case, a
heat transfer out.  Entropy is then transferred out.  If the temperature
of the environment is constant, then the amount of entropy transfer is:

dS = dQ/T   [2, p.150, equation 5.11]

dS : differential change in entropy of environment (entropy transfer)
dQ : incremental heat transfer to environment 
T : temperature of environment (absolute)

if dQ is positive - heat transfer to environment
then dS is positive - increase in entropy of environment

>>What about the order of the snowflake?  A snowflake indeed appears to have
>>a high degree of order, but remember, we are talking about ordered energy.
>
>We're talking about ordered water molecules.  Not energy.

I thought we were talking about thermodynamics.  Go back and read the
definition of thermodynamics.  Molecules depend heavily on energy to
even stay together.  Molecular bonds ring a bell?  Bonding *energy*?
Latent heat?

>Paul J. Schinder
>NASA Goddard Space Flight Center
>schinder@leprss.gsfc.nasa.gov

James P. Henley Jr.
Chemical Engineering Dept.
Auburn University