What You Need:
- Clay and glass bottle
- Draw a face on both ends of a large marshmallow.
- Drop the marshmallow into a glass bottle.
- Take a straw and wrap the clay around it about 1-inch away from the end such that the clay forms a ring around the straw.
- Place the short end of the straw into the bottle. The clay should stop the straw from dropping all the way into the bottle.
- Now press the clay around the mouth of the bottle so that the bottle is completely sealed and no air can get in (or out).
- Stand in front of a mirror so you can see the face on the marshmallow. Suck air out of the bottle. Make sure there are no leaks in the clay.
- Now stop sucking on the straw.
Although a marshmallow appears to be solid, it is actually filled with many pockets. These pockets are filled with air, like in a sponge. When you suck the air out of the bottle you are decreasing the pressure inside the bottle, which causes the spongy marshmallow to expand. When you stop sucking on the straw and remove the straw from your mouth the air rushes back into the bottle, increasing the pressure and causing the marshmallow to return to its original size.