Themes > Science > Chemistry > Inorganic Chemistry > More Information About Gas Laws > Gas Index > Real gases

While the ideal gas law doesn a very good job of predicting gas behavior, it's not perfect. Real gases differ in two major ways from an ideal gas
  1. Particles in a real gas have volume. This means that not all the volume in a container is available to the gas: the actual volume the particles have to move around in is Vreal = V-Vpart, where Vpart is the volume of the particles in the gas
  2. Particles in a real gas attract each other in general.

The effects of the particle volume are seen mostly at high pressure, where a lot of molecules are packed into a small space. Interparticle attraction comes in at low temperature: since the average velocity of a gas particle is proportional to the sqaure root of the temperature, as the temperature lowers the particles move more slowly, allowing them more time to interact. (If the temperature drops low enough, the forces become so strong that the particles begin to stick together, forming a liquid.)

Therefore, gases behave most like ideal gases at low pressure and high temperature: low T and high P causes gases to behave non-ideally.


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