Blowing up Peeps: An experiment in thermodynamics

Here’s a video showing a lesson in thermodynamics with Peeps. Yes, Peeps.

(If you don’t know what Peeps are, they are marshmallow candies in animal shapes. They used to appear in stores at Easter time but now are found year-round.)

Carl Nelson, chief scientist and exhibits director at Imagination Station, a nonprofit science center in Toledo, does the honors in this video. Here’s the write-up from Imagination Station on what you will see:

The balloon and Peeps expand as the air pressure in the chamber is reduced by the vacuum pump. Peeps contain millions of tiny air pockets inside the gelatin/sugar mixture they made of. As the air expands inside the Peep, it pushes against the walls of the air pockets and eventually tiny rips and tears form between the air pockets that allows the air to escape. Once the air stops flowing out of the peep, the force exerted on the Peep relaxes a bit and it begins to slowly shrink. Allowing air to rush back inside the chamber further crushes the Peeps as the air slams into them.

Kristina noticed that the Peeps felt cold when touched. From a thermodynamics perspective, the tiny air pockets inside do Work as they expand. The energy used to do this Work on the walls of the pockets reduces the internal energy of the air inside the peep and it’s temperature drops, thus cooling the Peep.

The shaving cream grows large for the same reason as the Peeps. When the air is suddenly returned to the chamber the foam is much more dramatically crushed since it has a much weaker physical structure than the gelatin/sugar mix used in the Peeps.

Valerie Strauss covers education and runs The Answer Sheet blog.
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Valerie Strauss · April 20