Ideal Gases vs. Real Gases An ideal gas is a theoretical gas which perfectly fits into the equation PV= nRT. An ideal gas is different from a real gas in many ways. An ideal gases' mass can be disregarded in the equation because it has none; this is because an ideal gas is said to be a particle and particles do not have any mass. Ideal gases obtain no volume unlike real gases which obtain small volumes. Also, since ideal gas particles excerpt no attractive forces, their collisions are elastic. Real gases excerpt small attractive forces. The pressure of an ideal gas is much greater than that of a re