For this experiment, kids need only their own hands and cubes of ice. Have the kids rub their hands together until they start feeling warm. Tell the kids that this warmth is caused by friction, which occurs when two objects rub together. Have each child pick up a cube of ice, hold it over a sink or bowl and watch how the heat of their hands melts the ice. This is simple conduction of heat from their skin to the ice, and it's a good way to demonstrate how quickly and easily heat can be conducted through the skin.
Kids love eating chocolate and playing with food, so this experiment is the perfect blend of science, cooking and snacking. Take a bowl and place it in a pan of very hot water. Pour a cup of semisweet chocolate chips into the bowl -- making sure not to get any water in with the chocolate -- and have the kids stir the chocolate chips with a spoon and notice how they gradually melt. This shows them that heat is being conducted from the hot water through the metal of the bowl to the chocolate chips. As a final activity, let the kids dip strawberries into the chocolate and eat them as a snack.
Different materials conduct heat at different rates, and this experiment will let the kids measure those differences. Take a ceramic or glass bowl and several objects, including a wooden pencil, a plastic ruler and a metal spoon. Place hot water in the bowl and then lean each of the objects against the side the bowl. Use a small amount of modeling clay to hold the objects to the side of the bowl. Take a bit of butter or shortening and stick a plastic disk or poker chip near the top of each item. Have the kids measure the time it takes for the heat to travel up each object, melt the butter or shortening and cause the plastic disk to slide off. This will show them the different conducting rates of wood, plastic and metal.
Pour hot chocolate into a glass cup, a plastic cup, a Styrofoam cup and a coffee mug. Have the kids pick up each one and see which is hottest and which is coolest; the one that is hottest is the best heat conductor and the one that is coolest is the best insulator. This experiment demonstrates the difference between a conductor and an insulator, and how some materials work best as conductors while others work best as insulators, based on the speed and intensity of their conductivity. And at the end of the experiment, the kids can have the added bonus of drinking the hot chocolate.