Pick up the hand boiler and gently squeeze it. As you hold it, the liquid will travel up to the top—not because you squeezed the boiler, but because the heat from your Hand warms the gas inside, which pushes the liquid into the top chamber.
A hand boiler highlights the interplay between temperature and pressure. The liquid will move from an area of higher pressure to an area of lower pressure. When the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be in direct proportion.
The Hand Boiler recommended for ages 7+.