4.2a Heat moves in predictable ways, flowing from warmer objects to cooler ones, until
both reach the same temperature.
4.2b Heat can be transferred through matter by the collisions of atoms and/or mole-
cules (conduction) or through space (radiation). In a liquid or gas, currents will facilitate
the transfer of heat (convection).
4.2c During a phase change, heat energy is absorbed or released. Energy is absorbed
when a solid changes to a liquid and when a liquid changes to a gas. Energy is released
when a gas changes to a liquid and when a liquid changes to a solid.
4.2d Most substances expand when heated and contract when cooled. Water is an
exception, expanding when changing to ice.
4.2e Temperature affects the solubility of some substances in water.