- Develop a conceptual cause-and-effect model for the phase change process that shows the relationship among particle attraction, particle motion, and gain or loss of heat - when a solid melts it has absorbed heat that increased the potential energy of its particles (space between particles) thus reducing the attraction between particles so that they can flow in a liquid phase. (Consider conditions of normal atmospheric pressure as well as the qualitative affects of changes in pressure involving gases.)
- The focus should be on the following phase changes: solid to liquid (melting), liquid to gas (vaporization), gas to liquid (condensation), and liquid to solid (freezing).
- Compare the process of evaporation to vaporization – materials that evaporate verses those which do not; attraction between surface particles and colliding air molecules.
- Recognize that the formation of solutions is a physical change forming a homogenous mixture