Find out if you're "hot" when you experiment with the relationship between temperature and pressure. Just wrap your hand around the bottom bulb and the liquid will go up to the top - not because the kids squeezed the boiler, but because the heat from their hands warms the gas, which pushes the liquid into the top chamber. After a little while, challenge your students to get the liquid back to the bottom of the boiler without turning it over. Works on the same principle as the old Love Meter, common in drugstores and five-and-dimes all over America.
