For this reason, many students are taught the three most important gas laws by the names of their discoverers. What happens to the volume of a gas as the pressure on it changes. Let's try the following experiment using equipment that might be found in your kitchen. Marshmallows in a kitchen vacuum pump. Do try this experiment at home.
Marshmallows are a mixture of sugar, air, and gelatin.
The sugar makes them sweet, the air makes them fluffy, and the gelatin holds everything together. Marshmallows are a frozen foam, if you will, and are mostly air by volume. When placed in a vacuum pump, they expand as the pressure decreases. Break the seal on their container and they shrink during the return to normal atmospheric pressure. Since the vacuum pump pulls on the marshmallows hard enough to burst some of the air bubbles, they are actually a bit smaller and more shriveled at the end of this experiment.