The average kinetic energy of a molecule is closely related to the temperature of its environment, and this determines how fast the molecule is moving. On average, the speed of any molecule is close to 300 m/s, which is equivalent to covering the distance of a few football fields every second! The other important thing to realize, though, is that collisions with other molecules are constantly causing changes in direction, which slows the overall distance in a given direction that a molecule travels.