Features and High Quality Hand boiler - heats the liquid using body temperature. Cup the lower chamber in your palm and observe the liquid rising through the tubes into the top chamber Hand Boilers are glass sculptures with a looped design containing a liquid that reacts to heat from your hand. After removing from your hand, it takes a few minutes for the liquid to cool and return to the lower chamber. This science toy demonstrates thermal energy transfer. Available in multiple colors such as blue, green, yellow, purple, and red, with various loop designs. Item shipped at random based on availability. Demonstrates principles of gas behavior and vapor-liquid equilibrium. The colored liquid is a mixture with a boiling point slightly above room temperature. Heat from your hand causes evaporation, creating gas pressure that pushes the liquid upward. When cooling, the gas condenses and flows back to the lower chamber. Package includes 1 x hand boiler