ABSTRACT
Unlike liquids or solids (see Chapter 5), in which molecules are essentially touching one another, gases consist of well-separated molecules that touch each other only when they collide. Typically, at normal temperatures, gas molecules are travelling at speeds of a few hundred metres per second, although the distance they travel between collisions is only about 10-7 metres. The molecules in a gas are therefore constantly colliding with one another several billion times each second.
