Hand boiler – boils the liquid with your own body temperature. Cup the lower chamber in your palm and watch how the liquid boils and rises through the tubes into the top chamber. Hand Boilers are looped and twisted glass sculptures containing a liquid that will “boil” as heat is transferred from your bare hand. Once out of your hands, it takes a few minutes for the liquid to cool down and return to the large bulb. It is a pretty fascinating science toy and an excellent demonstration of energy transfer.
Hand boilers demonstrate Charles’s Law and vapor-liquid equilibrium. The colored liquid in the boiler is comprised of a volatile mixture of liquids that have a boiling point just above room temperature. The body heat from your hand causes the liquid to boil, which in turn makes the liquid evaporate, turning it to gas. The expanding gas pushes the liquid upwards and when you release your hand, equilibrium is re-established. The gas condenses into a liquid again and flows back into the lower bulb.