Courses: P3, P13
Safety: Make sure to supply cryogenic gloves and splash goggles (despite Yorke using neither in the video...)
This demo can be done with a balloon filled with air or with helium. With a helium balloon it will sit on the table once chilled, but as it warms it will eventually float up into the air.
Another good variation on this demo is to connect a helium balloon to an air filled balloon. The HE balloon will have sufficient buoyancy to lift the air filled balloon, but if you cool the air filled balloon in liquid nitrogen, the HE balloon will no longer be able to lift it. (2B40.29)
Equipment: Styrofoam box, Dewar of LN2, Cardboard box with a few balloons -- tape helium balloons to bottom of box, cryogenic gloves, splash goggles.