What happens to a gas when it expands adiabatically?

When a gas is expanded through an adiabatic valve, sometimes its temperature decreases. Sometimes, however, its temperature increases. There are even situations where the temperature of the gas doesn't change at all. What's going on? James Joule and William Thomson tried to answer this question in the 1850's by performing a set of careful experiments along with a detailed theoretical analysis. In honor of their pioneering work, the adiabatic expansion of a gas of often referred to as a "Joule-Thomson expansion", and the temperature change upon expansion is called the "Joule-Thomson effect".

In this module, you will investigate the Joule-Thomson effect, using classical thermodynamics along with molecular simulation. You will explore how the relationship between temperature, pressure and intermolecular forces leads to a given temperaure change upon expansion. At the completion of the module, you should be able to answer Joule and Thomson's question!

Last modified:July 10, 2001