1) Simply wrap your hands around the hand boiler. You don’t need to squeeze tight. Then watch the gas push the liquid from the bottom to the top. The liquid mY bubble and appears to boil. But not for everyone.
The heat from your hand transfers to the liquid in the bottom of the boiler. This increase in temperature causes the pressure inside the bulb to rise. As a result the liquid moves to the top of the hand boiler bulb. After almost all of the liquid has moved from the bottom to the top of the boiler, the remaining liquid starts to move up tube to the top of bulb. It creates bubbles in the liquid at the top and it appears to boil. Hence the name “Hand Boiler”.
When containers are kept closed an interesting relationship exists between temperature and pressure. The more the temperature increases, the more the pressure increases. Molecules of gas inside the container move faster as the temperature rises and pressure increases.
Over the years that I have use these hand boilers it always interesting seeing who can make the hand boiler appear to boil. Temperatures of people are not exactly the same. Some are more hot than others!