Lesson 1: Gases

This lesson will introduce you to the behavior of gases. In particular, we will study "ideal gases," those gases whose behavior follows a set of simple physical laws derived from elementary physics.

In fact, as you will see, all gases behave "ideally" when the pressure is low enough and the temperature is high enough. For many gases, these conditions occur at room temperature and normal atmospheric pressure.

Gases are characterized by molecules (or atoms) that are very far apart compared to their size. As a result, gases are mostly empty space. They have very low density and are easily compressible. The gas particles move at very high speeds, colliding with each other and with the walls of their container. They therefore have no fixed volume and no characteristic shape of their own. They naturally expand to fill whatever container they are in and, if the container is not sealed, will easily escape.

The physical properties of gases are largely specified by the amount of gas present (in moles), pressure, volume (when in a container), and temperature.

Before you begin this lesson, and periodically while you are going through it, you will want to review the objectives listed in the Objectives page. When you have completed the lesson, be sure and try the self-quiz.