Heat is also produced by friction and light . You can easily feel the heat produced by friction just by rubbing your hands together -- the mechanical rubbing of your hands gets turned into the motion of molecules in your hands, i.e. heat. Similarly, you can feel the heat produced by light by sitting out in the sun. The light hitting your skin pushes the molecules in your skin about -- creating heat.
This exploration encourages thinking about how heat transfers between objects, using ice cubes as examples. As heat gets transfered to the ice cube, it melts more and more. Heat comes through whatever it is touching, from air that it contacts, and through the sides of its container.
Different materials have different properties of transfering heat. For example, hot coffee in a metal cup will hurt your hand, but in a styrofoam cup it can be handled. The molecules in the metal are all touching each other (i.e. close contact). The styrofoam is light and full of air -- it's molecules are often separated from each other.