A true story. A thermodynamics professor had written a take home exam for his
graduate students. It had one question:
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, 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.
Of course, if hell is expanding at a rate faster than the increase of souls
in hell, than the temperature and pressure will drop until hell freezes over.
The student got an A on the exam. 
