Chapter 8
When the attractive forces between molecules overcome the random thermal kinetic energy that keeps molecules apart in the gas phase, the molecules cluster together so that they can no longer move about freely, and enter the liquid or solid phase. Because of their smaller volume relative to gases, liquids and solids are often referred to as the condensed phases. The relative order of kinetic energy among the three different phases of matter is one of the most important concepts to keep in mind. Molecules move most quickly in gases, flow more slowly in liquids, and merely vibrate in solids.