Marshmallow Mashers

Marshmallows are a tasty, fluffy staple of summertime s’mores, camp-outs, and backyard barbecues. There really isn’t very much to them, either. The scientific way to see what really fills a marshmallow is to put it to the Marshmallow Masher test. You use a property of air to demonstrate what’s really on the inside of those roasted ‘mallows you make around a campfire. It’s not all sugar. You can use this activity to study the effects of atmospheric pressure. People sometimes refer to things being “as light as air,” but the truth is that the air surrounding Earth weighs a lot and exerts considerable pressure on its surface. The atmospheric pressure at sea level is 14.7 pounds per square inch (76 cmHg). That’s roughly two gallons of milk on top of each square inch (6.5 sq cm)! Consider that a typical large marshmallow has a surface area of about 6 square inches (39 sq cm). So, the marshmallow has about 88 pounds of atmospheric pressure (455 cmHg) being exerted upon it (6 square inches x 14.7 pounds per square inch = 88.2 pounds)!

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