As the Easter Bunny hops off for another year, many parents are left contemplating the mountains of candy left in his wake. Once the favorites are gone, rather than tossing the less-popular leftovers, put that Peep to scientific use.

Peeps, the chick-shaped marshmallow treat manufactured by the Just Born Candy Company, have expanded in recent years to allow for other holiday marketing. However, Easter baskets remain the Peep’s traditional nesting ground. This popular treat comes in multipacks, meaning you should have plenty to execute a few experiments.

Marshmallows are made mainly from sugar, gelatin, and water. The mixing process introduces air pockets. That air behaves in interesting ways depending on the environment. Put the treat in the freezer for a few hours and make observations. Did it shrink a little? What happens if you put a Peep in the microwave? It gets much bigger before collapsing into a sticky heap. What’s going on?

The answer lies in the Peep’s internal air pockets. We think of air as being empty, but it’s made up of molecules. When molecules cool down, or lose energy, they get closer together. When molecules heat up, or gain energy, they move farther apart. The air inside the marshmallow takes up less space when it cools, shrinking the Peep. The microwave heats the air, causing the confection to expand. That rapid expansion also causes some of the sugary pockets to rupture, meaning the treat will “collapse” once the air cools to room temperature.

The heat-related expansion properties of the Peep allow for further fun: Peeps Jousting. A quick Internet search will deliver more details, but in a nutshell: Two marshmallow “combatants,” armed with toothpicks, enter the microwave “arena.” As they expand, the first one to pierce the other wins. While each contender gets only one round before being reduced to a sticky mess, win or lose, this is one sweet competition.

First Published: April 14, 2016, 4:00 a.m.