<P> The Joule expansion , treated as a thought experiment involving ideal gases , is a useful exercise in classical thermodynamics . It provides a convenient example for calculating changes in thermodynamic quantities , including the resulting increase in entropy of the universe ( entropy production ) that results from this inherently irreversible process . An actual Joule expansion experiment necessarily involves real gases ; the temperature change in such a process provides a measure of intermolecular forces . </P>
<P> The Joule expansion , treated as a thought experiment involving ideal gases , is a useful exercise in classical thermodynamics . It provides a convenient example for calculating changes in thermodynamic quantities , including the resulting increase in entropy of the universe ( entropy production ) that results from this inherently irreversible process . An actual Joule expansion experiment necessarily involves real gases ; the temperature change in such a process provides a measure of intermolecular forces . </P>
expansion of a perfect gas into vacuum is related with
expansion of a perfect gas into vacuum is related with
entropy
entropy