Overview of The Ideal Gas and Kinetic Theory
The ideal gas is an imaginary construct. Like the incompressible fluid or the frictionless inclined plane, the ideal gas was developed to make certain kinds of discussion possible. The ideal gas enables the discussion of basic thermodynamic relationships without the need for endless reservations. An ideal gas consists of perfectly spherical particles of zero volume that may only collide elastically. Because the particles may only interact through elastic collisions, as a system, an ideal gas may only possess internal energy in the form of the translational kinetic energy of the particles. There are no places for rotational or vibrational kinetic energy, and there are no intermolecular forces within an ideal gas. There is no electrostatic potential energy. One very important consequence of this restriction is that the internal energy of a given amount of ideal gas may be directly determined from the temperature. Another crucial consequence is that tthe thermodynamic state of the ideal gas may be specified by any two of the pressure, volume, and temperature.
The Ideal Gas and Kinetic Theory on the MCATIn my opinion a good understanding of Thermodynamics is one of the most important steps to an integrated conceptual understanding of science, so the importance of this chapter, as well as all of the other topics from this week and next week cannot be understated. In addition the importance of the Ideal Gas and Kinetic Theory to the overall learning progression, this material will show up in conceptual questions and quantitative questions. Generally, the writers of the MCAT are more interested in your conceptual understanding of physics and chemistry than your ability to solve number problems, so the balance with MCAT physical sciences questions will lean more towards conceptual questions than quantitative questions. However, usually there will be a half dozen or so physics questions that require quantitative problem solving, so it is important to give a bit of extra attention to the categories that have often given rise to quantitative questions. On many MCATs there have been quantitative problems involving the Ideal Gas Law as well as portions of Kinetic Theory such as Graham's Law.