This experiment teaches principles of pressure, properties of foam, and ocean science. Uh, what do marshmallows have to do with the ocean? With this demonstration, you'll be able to basically see the effect of deep-sea pressure on just one marshmallow from the book Try This! Extreme by Karen Romano Young.
Draw a face or letter on the marshmallow. (This will help you see how it changes under pressure.)
Pull the plunger of the syringe all the way out, and insert a marshmallow. Replace the plunger.
Suck out the air by pulling the plunger. Observe the results.
Push the plunger back in. Observe the results.
WHAT'S GOING ON
The marshmallow may look solid, but it’s actually full of air pockets—a foam. When you pump air in, you increase the pressure on the marshmallows and the air inside them is compressed. When air rushes back in, the marshmallows may get larger—and if you suck it out they may get smaller.