Sunday, March 23, 2008

Peeps Chemistry

There is a long and glorious tradition of torturing leftover Easter candy. At the site Peep Research, the fear response of a Marshmallow Peep is measured through exposure to heat in a microwave. But many of the more sophisticated Peeps experiments can probably not be done at home. While you can replicate the vacuum experiment above (by Seaford, NY chemistry teacher Edward Kent, who has many other interesting demonstration videos on his website) by using an ordinary Kitchen Vacuum Packer as shown on the Steve Spangler website, the explosive liquid oxygen video should be only be done under laboratory conditions.

More Peepy links at Peep-O-Rama including Martha Stewart's recipe for fresh, homemade Peeps (sort of an oxymoron). Also solubility tests by a stuffed chemistry mascot mole.

Oh, and here's the chemistry explanation, from the Exploratorium's Science of Cooking website:

Marshmallows are mostly sugar and water wrapped around a bunch of air bubbles. When you cook marshmallows in your microwave oven, several things happen at once. The microwave makes the water molecules vibrate very quickly—which makes the water heat up. The hot water warms the sugar, which softens a little. The hot water also warms the air bubbles.
When you warm air in a closed container, the gas molecules move around faster and push harder against the walls of the container. As the air in the bubbles warms up, the air molecules bounce around faster and faster and push harder against the bubble walls. Since the sugar walls are warm and soft, the bubbles expand, and the marshmallow puffs up. If it puffs up too much, some air bubbles burst, and the marshmallow deflates like a popped balloon.
When you take the marshmallow out of the microwave and it cools off, the bubbles shrink and the sugar hardens again. When the microwave marshmallow cools, it’s dry and crunchy. We think that’s because some of the water in the marshmallow evaporates when the marshmallow is hot. If you cook your marshmallow for too long, it turns brown or black inside. That happens when the sugar gets so hot that it starts to burn [known as caramelizing].

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