Features Hand boiler - heats the liquid with your body temperature. Cup the lower chamber in your palm and observe the liquid rising through the tubes into the top chamber Hand Boilers are looped and twisted glass sculptures containing a liquid that reacts to heat transferred from your hand. After removing your hand, it takes a few minutes for the liquid to cool and return to the lower chamber. This science toy provides an engaging demonstration of energy transfer. Hand Boilers are available in various colors such as blue, green, yellow, purple, and red, and come in different loop designs. The style you receive will be randomly selected and shipped. Hand boilers illustrate Charles's Law and vapor-liquid equilibrium. The colored liquid inside is a volatile mixture with a boiling point slightly above room temperature. Heat from your hand causes the liquid to evaporate into gas. The expanding gas pushes the liquid upward. When the heat source is removed, the gas condenses back into liquid and flows to the lower chamber. Package includes 1 x hand boiler