Ideal Gasses

An ideal gas is any gas that obeys the ideal gas law (see the ideal gas law lesson).  An ideal gas’ behavior is based on the assumption of the kinetic molecular theory of gases (see the kinetic molecular theory of gases lesson).   

It’s a hypothetical, non-existent gas that has no intermolecular forces that interact between the particles of the gas.  Particles of an ideal gas are infinitesimally small: while the gas itself takes up some volume of space, the individual particles are assumed to have no volume. Theoretically, ideal gasses comprised of these small particles move in a constant, random, linear motion.  

In reality, there are no ideal gasses.  However, real gasses can approach the behavior of ideal gasses at lower pressures and higher temperatures where intermolecular forces between the particles are minimized.  While not exact, ideal gas behavior is a useful initial model for understanding the behavior of real gases.