# Why use a cube as a reference volume in the kinetic theory of gases?

In basic kinetic theory we often use cubes. For example, the derivation of the ideal gas law is done with a cubical volume. Is a cube necessary for it to work? If not, wouldn't a sphere be more symmetric and thus simpler?

• Can you be more specific? – Aaron Stevens Feb 20 at 4:39
• Depends on the level of the presentation and the way you intend to balance hand-waving against grotty equations. – dmckee Feb 20 at 5:01
• Write out the derivation in (x,y,z). Write out the derivation in (r,$\Theta$,$\psi$). Compare. – Jon Custer Feb 20 at 23:50

Using a cube is an extension of the choice of coordinates used in the mathematical modeling. $$dV=dxdydz$$ is a small cube after all. $$dV$$ is more complicated in radial coordinates