PURPOSE: Amusing demonstration of Boyle's Law.

DESCRIPTION: A marshmallow is placed in a bell jar. As the air is pumped out of the jar the pressure inside becomes smaller and the little bubbles of air in the marshmallow increase in size, inflating the marshmallow. Eventually much of the air originally in the marshmallow is pumped aaway. When the air is let back in, atmospheric pressure compresses the marshmallow to a small fraction of its original size.

An alternative demonstration uses a balloon with a small amount of air in it in place of the marshmallow. The photographs below show the marshmallow: before pumping, after pumping, and after the air is let back into the bell jar, and the balloon: before pumping and after pumping.

SUGGESTIONS: BRING YOUR OWN MARSHMALLOWS! Do not place the marshmallow near the pump inlet; place the screen over the air intake and the marshmallow or the balloon on top of the screen.

REFERENCES: (PIRA unknown.) This is done on the infamous film loop "Boyled Marshmallows."

EQUIPMENT: Vacuum pump with bell jar, marshmallows.

SETUP TIME: None.