Charles’ Law – Hand Boiler. Hold the bottom for some cool bubbling action. Heat from your hand warms the air in the boiler causing it to expand. As a result, the air forces the liquid up the twisting glass tube and then bubbles through it. Demonstrate the power of energy transfer with this intriguing liquid motion gadget. Everyone is hot, hot, hot with this boiler. Colour and shapes vary. This is not a toy. Units: Each.