[Tigers] Laws of Thermodynamics

[Tod Brown]

Steve's original statement of the Laws of Thermodynamics as given by 
C.P. Snow are pretty succinct and an
easy way to remember them.  When stated in the usual language of 
physics, they do become a little less
clear to the layman.  Whichever way you prefer, I would add a couple of 
things as an attempt at clarification
and elaboration.

The First Law is also known as the Law of Conservation of Energy.  Most 
people have heard of this, but it
simply states that the total amount of energy in an isolated system is 
constant.  That is, energy can be
converted from one form to another, but cannot be created or destroyed.  
Automobile engines operated by
converting the chemical energy stored in gasoline into heat.  Engine 
modifications to gain power are involved
with finding ways to convert the energy content in gasoline into heat 
more rapidly.  Power is the measure of
how fast energy is being converted.  You can, of course, use gasoline 
with more energy content (i.e. higher
octane) as well, but the principle remains - energy in = energy out.

The Second Law, also known as the Law of Entropy, concerns itself with 
more practical matters.  It basically
says that energy conversions involve "losses".  Most of the time these 
losses appear as heat, which is just
the random motion of molecules.  In an automobile engine, when the 
chemical energy stored in the gasoline
is converted into motion of the engine, some of the energy is also 
converted to heat due to friction.  This
turns out to be quite a bit of energy, so most automobile engines are 
not very efficient devices.  The Second
Law also explains why many processes, even though they do not violate 
the First Law, are not seen to take
place.  That is why many processes that can be observed in a film run 
backwards seem so strange - they
represent processes which diminish the amount of Entropy (or disorder) 
in a system.  Put simply, things run
downhill spontaneously, not uphill.  It is on the basis of this law that 
perpetual motion devices are precluded. 
One can get into a lot of philosophical discussions with the Law of 
Entropy and the implications it has for the
direction of time, etc.  One other interesting aspect of this law is 
that it is not absolutely true, in the sense
that it is a statement of statistical probabilities. 

Finally, these laws operate whether we wish them to or not.  
Consequently, it would, indeed, be helpful if
those who determine the policies of our government with regard to energy 
could take the time to understand
them.  The comments of a couple of folks in this forum regarding the 
conversion of corn into ethanol and the
possibility of using hydrogen power for vehicles might be better 
understood in light of these laws.

Tod
B382002384LRXFE
(constantly generating entropy in my little corner of the universe)