Features 100% hand boiler - activates the liquid using body heat. Cup the lower chamber in your palm and observe the liquid rising through the tubes into the top chamber due to thermal energy transfer. Hand boilers are glass sculptures with a looped design containing a colored liquid that responds to heat from your hand. When removed from hand contact, the liquid gradually cools and returns to the bottom bulb. This science toy demonstrates principles of energy transfer, Charles's Law, and vapor-liquid equilibrium. The liquid inside is a volatile mixture with a boiling point slightly above room temperature. Heat from your hand causes the liquid to evaporate, creating gas pressure that pushes the liquid upward. Upon cooling, the gas condenses and flows back down. Available in various colors such as blue, green, yellow, purple, and red, with different loop shapes. Item shipped at random based on availability. Package includes 1 x hand boiler.