Kinetic Molecular Theory

 Guidelines for reading the material with great comprehension.
 Gases are one of the most pervasive aspects of our environment on the Earth. We continually exist with constant exposure to gases of all forms.
   The steam formed in the air during a hot shower is a gas. The Helium used to fill a birthday balloon is a gas. The oxygen in the air is an essential gas for life.
 A windy day or a still day is a result of the difference in pressure of gases in two different locations. A fresh breeze on a mountain peak is a study in basic gas laws.  

To fully understand the world around us requires that we have a good understanding of the behavior of gases. The description of gases and their behavior can be approached from several perspectives. The Gas Laws are a mathematical interpretation of the behavior of gases. However, before understanding the mathematics of gases, a chemist must have an understanding of the conceptual description of gases. That is the purpose of the Kinetic Molecular Theory.

This presentation will be broken down into three parts.

 Kinetic Molecular Theory

The Kinetic Molecular Theory is a single set of descriptive characteristics of a substance known as the Ideal Gas. All real gases require their own unique sets of descriptive characteristics. Considering the large number of known gases in the World, the task of trying to describe each one of them individually would be an awesome task. In order to simplify this task, the scientific community has decided to create an imaginary gas that approximates the behavior of all real gases. In other words, the Ideal Gas is a substance that does not exist. The Kinetic Molecular Theory describes that gas. While the use of the Ideal Gas in describing all real gases means that the descriptions of all real gases will be wrong, the reality is that the descriptions of real gases will be close enough to correct that any errors can be overlooked.

  1. The gas consists of objects with a defined mass and zero volume.
  2. The gas particles travel randomly in straight-line motion where their movement can be described by the fundamental laws of mechanics.
  3. All collisions involving gas particles are elastic; the kinetic energy of the system is conserved even though the kinetic energy among the particles is redistributed.
  4. The gas particles do not interact with each other or the with the walls of any container.
  5. The gas phase system will have an average kinetic energy that is proportional to temperature; the kinetic energy will be distributed among the particles according to a Boltzmann type of distribution.

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Updated September 1, 2000