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Kinetic Molecular Theory

Theory of the ideal Gas


Ever see a fast food commercial. Don't those burgers look great.  Then you get one, and you are disappointed because it is not the perfect one on the TV. So you lie to yourself.

No matter how many burgers you order in your life, none will be as perfect at the one on TV. But if you think it is perfect, who really cares.


Ideal gas are like the commercials and real gases are what you get. Nothing is ever perfect, but close is good enough.

Ideal Gas Rules (the Kinetic Molecular Theory)

  1. Gases consist of large numbers of molecules (or atoms, in the case of the noble gases) that are in continuous, random straight line motion

  2. The volume of all the molecules of the gas is negligible compared to the total volume in which the gas is contained (This is equivalent to stating that the average distance separating the gas particles is large compared to their size).

  3. Attractive and repulsive forces between gas molecules is negligible (they can never group together and form drops and liquefy)

  4.  Energy can be transferred between molecules during collisions, but the collisions are perfectly elastic and the total energy remains constant.


Here is what you really need to know.

1. The most ideal gas in nature is hydrogen then helium. It is small and has the least mass.

2. How real gases deviate from Ideal gases.

    They have mass, volume and attraction. this causes the molecules to be drawn to each other, which cause the actual volume of a gas to be smaller then its ideal gas calculation. 

Watch this simulation of how a real molecules would wobble as it travels.

AP Chemistry-The Van der Waals equation accounts for these shortcomings of the Theory of the Ideal Gas.

3. Also real gases can liquefy under the conditions of High Pressure and Low Temperature. These are the least ideal conditions.

 Just like ideal gas conditions, Ideal Vacations  conditions High Temperature and Low Pressure. 

Chemical Demonstration Videos