This is part three of a two week unit on heat and energy. For many students this will be their first exposure to a quantitative study of heat. The focus is on a conceptual understanding of heat as a form of energy as well as mastery of simple quantitative problems, including changes of state. Introduce inter-particle forces. Most simple substances can be converted to liquids or gases by heating them, or turned into solids by cooling them.
Hot objects store thermal energy which is released as the objects cool.
One unseen fact is that the transformations from solid to liquid or liquid to gas usually require enormous amounts of thermal energy. For example, on a warm day a glass containing melting ice will absorb a lot of heat energy while the ice is melting. The mixture will always remain at 0 o C until all the ice is melted. This is because all the absorbed heat is changing the solid to a liquid, and therefore in not able to increase the temperature of the mixture. Steps a to b above.