Repeat with aluminum foil. Have them describe that the more surface of clay that touches the water the more likely it will float. Carefully insert 10-12 toothpicks into the ball of clay to try to determine what the object is inside the clay. Stop and solicit observations by students. Introduce idea that their movement took energy and that movement changed to heat.
Some materials transfer heat energy better than other materials.
Have a long thermometer inserted in the punctured cap so that temperature can be read without removal of the thermometer. One jug is the control with NO wrap. Have students read the thermometers every half-hour keeping a data table. Student teams will have 3 to 4 different magnets.