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 real gas since its particles lack the attractive forces which hold the particles back when they collide.  Therefore, they collide with less force.  The differences between ideal gases and real gases can be viewed most clearly when the pressure is high, the temperature is low, the gas particles are large, and when the gas particles excerpt strong attractive forces.  Monoatomic gas molecules are much closer to ideal gases than other particles since their particles are so small.  Because of the differences between ideal and real gases, Van der Waals created an equation to relate the two.

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