Gas and the Size of a Marshmallow

In this family STEM activity, students explore the science behind the size of a marshmallow. What happens if you add or remove air around a marshmallow? Families can see science in action by experimenting with stretchy, gooey marshmallows.

Gas Inside and Gas Outside

Marshmallows contain hidden gas that is trapped inside when they are made. Balanced by the gas (air) outside, marshmallows stay a certain size. But by manipulating the air surrounding a marshmallow, you can force a marshmallow's size to change and observe important laws of chemistry in action.

In this week's family science activity, students use a vacuum pump to remove air from a jar in which marshmallows have been placed and see what happens. How do the marshmallows change? Why? Once air is allowed back into the jar, kids will observe something else happen. Do the marshmallows change again? Why? The activity also guides a related exploration using a microwave to heat marshmallows and observe what happens after they are heated and as they cool.

The following Science Buddies activity on the Scientific American website has all the information you need to do this science activity with your students at home: Puffing Up Marshmallows.

Making Connections

Students interested in the science questions and principles demonstrated by this family science activity, or in other experiments using marshmallow, may also enjoy the following hands-on science projects and activities:

• Boyle's Law: Pressure vs. Volume of a Gas at Constant Temperature
• Charles's Law: Volume vs. Temperature of a Gas at Constant Pressure
• Circus-Trick Science: How to Balance Anything
• Make Your Own Marshmallows
• Mixing Your Own Marshmallows: Finding the Right Ratio of Sugar to Corn Syrup