Density in Action: Can You Sink a Marshmallow?
By Loralee Leavitt, Candy Experiments
At the USA Science and Engineering Festival in Washington, DC, children crowd around the Candy Experiments booth. A volunteer asks if they’re ready to take the marshmallow challenge: “Can you sink a marshmallow?”
As Steve Spangler teaches in the lemon and lime sink-and-float experiment, an object sinks if it is more dense than water. It floats if it is less dense than water.
When you drop a marshmallow in water, it floats like a balloon. A marshmallow is full of air bubbles, which puff it out. The sugar in the marshmallow gets spread out over a large area, making the marshmallow less dense than water. So how do you make a marshmallow denser? You have to make it smaller.
To try the marshmallow challenge, take a mini marshmallow and squash it. You can do this by smashing it between your palms, rolling it between your fingers, or smashing it against a flat surface. Try to roll it into a ball rather than flatten it into a pancake, because a pancake shape floats better than a ball.
When your marshmallow is as small as you can make it, drop it in water. Does it sink? If it does, you’ve made it denser than water. You beat the marshmallow challenge!
If that was too easy, try a harder challenge: sinking a regular marshmallow. Squash or roll it on a cornstarch-covered cutting board to keep it from getting too sticky. (Otherwise, you may have to scrape the marshmallow goo off your hands with a spoon.) Then drop it in a water to see what happens. You can also try this experiment with Peeps, 3 Musketeers, or other kinds of candy that float.
Loralee Leavitt destroys candy for the sake of science at www.CandyExperiments.com. Her new book, Candy Experiments, contains dozens of amazing experiments including creating giant gummi worms, turning M&Ms into comets, and growing candy crystals. Candy Experiments is available at Amazon.com.