Gases
Gases consist of large numbers of tiny particles. These particles, usually molecules or atoms, typically occupy a volume about 1000 times larger than occupied by the same number of particles in the liquid or solid state. Thus, molecules of gases are much further apart than those of liquids or solids. Most of the volume occupied by a gas is empty space. This accounts for the lower density of gases compared to liquids and solids, and the fact that gases are easily compressible. The particles of a gas are in constant motion, moving rapidly in straight lines in all directions, and thus passes kinetic energy. The kinetic energy of particles overcomes the attractive forces between them except near the temperature at which the gas condenses and becomes a liquid. Gas particles travel in random directions at high speeds. The collisions between particles of a gas and between particles and container walls are elastic collisions. An elastic collision is one in which there is no net loss of kinetic energy.
