A true story.  A thermodynamics professor wrote a take-home exam for 
his graduate students.  It had one question:

  "Is hell exothermic or endothermic?  Support your answer with a 
proof."

Most of the students wrote proofs of their beliefs using Boyle's Law 
or some variant.  One student, however wrote the following:

First, we postulate that if souls exist, then they must have some 
mass.

If they do, then a mole of souls can also have a mass.  So, at what
rate are souls moving into hell and at what rate are souls leaving?  I
think that we  can safely assume that once a soul gets to hell, it 
will not leave.  Therefore, no souls are leaving.

As for souls entering hell, lets look at the different religions that
exist in the world today.  Some of these religions state that if you
are not a member of their religion, you will go to hell.  Since, there
are more than one of these religions and people do not belong to more
than one religion, we can project that all people and all souls go to   
hell.

With birth and death rates as they are, we can expect the number of
souls in hell to increase exponentially.

Now, we look at the rate of change in volume in hell. Boyle's Law
states that in order for the temperature and pressure in hell to stay
the same, the ratio of the mass of souls and volume needs to stay   
constant.

So, exothermically, if hell is expanding at a slower rate than the 
rate at which souls enter hell, then the temperature and pressure in hell 
will increase until all hell breaks loose.

Endothermically of course, if hell is expanding at a rate faster than 
the increase of souls in hell, then the temperature and pressure will 
drop until hell freezes over.


(Ending 1)
It was not revealed what grade the student got.

(Ending 2)
"The girl beside me in class has stated that I will obtain sexual 
relations with her when hell freezes over.  Since that has not 
occured Hell must be exothermic. Q.E.D."