Growing & Shrinking Marshmallows - Cover Image

Growing and Shrinking Marshmallows

Vacuum packing Peeps marshmallows is an incredible (and delicious) demonstration of air!

A vacuum packer is an amazing device that vacuum packs food to seal in the freshness. At least that’s what those late night infomercials tell us. We’re more excited about using this fascinating device to explore the amazing properties of air pressure. Fill the special storage container with marshmallows (we prefer those adorable Peeps) and remove the air. Watch out! It’s the incredible growing marshmallow trick!

Adult Supervision Required – Not many kids have their own kitchen vacuum packer, so it goes without saying that adult supervision is required. Hey kids, you’ll have to fight for time with the vacuum packer machine after Mom and Dad figure this one out! Be sure to read and follow the manufacturer’s directions for using your specific kitchen vacuum packer.

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Experiment Materials

  • A kitchen vacuum packer
  • A vacuum packer storage container
  • Marshmallows of various sizes and types

Experiment Videos

Experiment

Growing & Shrinking Marshmallows - Step 1

1

Fill the storage container jar about half full with marshmallows and replace the lid.

2

Secure the lid that attaches to the special vacuum hose that came with the unit.

Growing & Shrinking Marshmallows - Step 3

3

Place the hose over the vacuum port on the lid and start the vacuum packer.

4

Don’t take your eyes off those marshmallows and watch them grow!

5

When the unit turns off, remove the hose.

6

Release the vacuum. Watch as the marshmallows shrink when the air comes rushing back into the container.

How Does It Work

The job of the vacuum packer is to remove the air from inside the storage container. Under normal conditions, molecules of air from the atmosphere (called atmospheric pressure) are pushing on the outside of the marshmallow. When the vacuum packer removes the air that was once pushing on the outside of the marshmallow, the air trapped inside the marshmallow pushes out (expands) causing it to get larger. The marshmallows shrink when the vacuum seal is broken and air rushes back into the container, reapplying the pressure onto the marshmallow.

Take It Further

Now that you understand the concept, try using a small balloon in place of the marshmallows or fill the storage container with soap bubbles. What would happen if you placed a small bag of potato chips into a large storage container and removed the air? Let’s say the goal was to shrink the marshmallows – how would you do it? Place the marshmallows into one of the plastic storage bags that came with the vacuum packer. When the air is removed from inside the bag, you get to see the power of the air in the atmosphere as it compresses the marshmallows. Also, see the Marshmallow Masher experiment.

Science Fair Connection

Growing and shrinking marshmallows is pretty cool, but it isn’t a science fair project. You can create a science fair project by identifying a variable, or something that changes, in this experiment.  Let’s take a look at some of the variable options that might work:

  • Try other items besides marshmallows such as gummy bears, Rice Krispies, baked goods, etc.  How much do these other items expand? What does this tell you about the amount of air inside of them?
  • Try different brands of vacuum packers. Which one expands the marshmallows the most? What does this tell you about their quality?

That’s just a couple of ideas, but you aren’t limited to those! Try coming up with different ideas of variables and give them a try.  Remember, you can only change one thing at a time.  If you are testing different liquids, make sure that the other factors are remaining the same.

Special Thanks

Thanks to Patti Duncan from High Point High School in Sussex County New Jersey for sharing this idea.