Free expansion is an irreversible process in which a gas expands into an insulated evacuated chamber.
Real gases experience a temperature change during free expansion. For an ideal gas, the temperature doesn't change, and the conditions before and after adiabatic free expansion satisfy
- pi Vi = pf Vf,
where p is the pressure, V is the volume, and i and f refer to the initial and final states.
During free expansion, no work is done by the gas. The gas goes through states of no thermodynamic equilibrium before reaching its final state, which implies that one cannot define thermodynamic parameters as values of the gas as a whole. For example, the pressure changes locally from point to point, and the volume occupied by the gas (which is formed of particles) is not a well defined quantity.
Famous quotes containing the words free and/or expansion:
“A majority, held in restraint by constitutional checks, and limitations, and always changing easily, with deliberate changes of popular opinions and sentiments, is the only true sovereign of a free people.”
—Abraham Lincoln (1809–1865)
“Artistic genius is an expansion of monkey imitativeness.”
—W. Winwood Reade (1838–1875)