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 as a concept to make certain kinds of discussion possible, clarifying the discussion of basic thermodynamic relationships. An ideal gas consists of perfectly spherical particles of zero volume. Ideal gas particles can only collide elastically. Because the particles may only interact through elastic collisions, as a system, an ideal gas only possesses internal energy in the form of the translational kinetic energy of the particles. There are no place within the system for rotational or vibrational kinetic energy, and there are no intermolecular forces within an ideal gas, so there is no place for electrostatic potential energy. One very important consequence of restricting internal energy to the translational kinetic energy of the particles is that the internal energy a given amount of ideal gas may be directly determined from the temperature. Another crucial consequence is that the thermodynamic state of the ideal gas may be specified by any two of the pressure, volume, and temperature.|
In my opinion a good understanding of Thermodynamics is one of the most important steps to an integrated conceptual understanding of science, so please pay special attention to this chapter, as well as the other topics from this module and the next. In addition the importance of the Ideal Gas and Kinetic Theory to the overall learning progression, this material will definitely appear in conceptual questions and quantitative questions on the MCAT. 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 leans towards conceptual questions away from quantitative questions. However, there will usually be a half dozen physics questions that require quantitative problem solving, so it is helpful to know which categories often given rise to quantitative questions, such as the Ideal Gas Law as well as portions of Kinetic Theory such as Graham's Law.