Educational Innovations’ website teachersource.com sells tons of unique science related items. One of those items is the handboiler. When you wrap your hand around the base the colored liquid (probably alcohol) heats up and moves up to the top where it eventually bubbles. My guess is that the molecules of the liquid speed up causing them to move up. When you let go the liquid eventually cools and goes back down via gravity. You can make the liquid go down faster by grabbing the top with your hand. I do this demo with student volunteers. We make observations and they hypothesize what is causing it. We also record who is able to send the liquid up the fastest.

Precautions: Don’t squeeze the handboiler. It can break easily.