Re: Why does a marshmallow expand in a vacuum?

What a fun experiment! And a great illustration of the ideal gas law! The marshmallow expanded because it contains air, which makes it so soft and fluffy. So, as you remove the air surrounding the marshmallow and reduced the pressure inside the bottle, the air bubbles inside the marshmallow expand proportionately:

PV = nRT

In this experiment, n, R and T are all constant (assume you are not losing any air from the marshmallow). So, if you reduce the pressure, the volume of air inside the marshmallow expands to reach an equilibrium with the surrounding pressure.

For more info on the Ideal Gas Law, search our MAD archives, using the term: PV

THanks for your question!

Kieran