O_TEXTBLOCK_TEXT When the metal bar is heated, the molecules next to the heat source move faster. The molecules bump into other molecules, making them move faster; those molecules then bump into other molecules, and their <HL Topic=Kinetic.tpc>KINETIC ENERGY</HL> makes the material hotter. Heat is passed, or conducted, from molecule to molecule by collision within the material.
E_QUEST1 Why is it easier to open a jar after you put it under hot water?
E_QUEST2 How does a stove produce heat energy?
E_QUEST3 When your hands are cold, what can you do to produce heat?
D_TEXTBLOCK_TEXT Heat is <HL Topic=Energy.tpc>ENERGY</HL> that flows from one body to another because of a temperature difference between them. Heat can change the temperature of a material or cause the material to expand.