Homeschool Discoveries

Sharing a few things I've discovered along the way…

Why Do Pop Cans Explode in the Freezer? (And Other Science Fun) July 15, 2012

Filed under: Science — kirstenjoyhill @ 10:55 pm

We ended up having a science-y sort of week this past week.  That wasn’t really planned!  I had intended to ease back into the school routine by just adding in history and spelling.  Of course, our science learning this week was mostly just a lot of fun!

Mr. E found the gigantic green caterpillar in our yard on Thursday night.  We had never seen anything like it!  After I very helpfully searched Google Images for  “Giant Green Caterpillar”, I was able to determine that it was most likely a Polyphemus Moth caterpillar. (This blog post was helpful — theirs looked just like ours!).   If it completes its metamorphosis it will become a very large brown moth.  We spent quite a while that evening watching it and letting it crawl on our hands.   We then let it go back on its merry way.  We haven’t seen it since then, but I am hoping it decides to make its chrysalis somewhere nearby so we can continue to observe!

Last Monday the kids planted seedlings while we were at the MN Children’s museum.  They sprouted on Friday and are now even bigger than they were in this picture.  We did a little bit of study of plants last spring, but we ran out of steam before the kids did any activities or demonstrations involving planting seeds.   They have been thrilled to check on the progress of their seedlings each day, and we aren’t even sure what kind of plants they are.  😉

And finally, I am so proud of myself for turning a random question into a real learning opportunity.  Miss M asked me while we were driving in the car on Friday, “Mom, why do pop cans explode when you put them in the freezer too long?”  She was remembering a time a number of weeks ago when Tony put a can of Dr. Pepper in the freezer and it made a giant mess.  It would have been really easy to just google the answer for her (since I didn’t know exactly off the top of my head, other than it probably had to do with the water expanding too much).

But instead, I asked her why she thought it might happen, and how she could teat her ideas.  At first, Miss M thought that maybe it was because soda pop might have baking soda in it, and that maybe things with baking soda are more likely to explode (like a baking soda/vinegar “volcano”!).  She figured out she could investigate that by reading the label on the can.  No baking soda there!  Next she suggested it was perhaps because it was too fizzy.  We couldn’t think of a good way to test that, so I hinted at other ideas.

Finally, she came up with the idea that maybe the pop might take up a different amount of space when frozen.  This is something we could test!

Our Hypothesis: A liquid expands in the freezer and has a greater volume when frozen.

Materials: Water, pop, clear glasses, baking soda (to also test Miss M’s baking soda idea with water), and a marker for the glasses

Procedure: We filled one glass with water, one with Dr. Pepper, one with water and baking soda, and one with “water and baking soda and salt and pepper” (at Mr. E’s suggestion!) 😉 We marked how full each glass was with a marker.  It was hard to see on the glass with the Dr. Pepper, so we added a mark with tape too.  We checked the glasses after two hours and also the next day!

Results: In the glass with the pop, the liquid seemed to expand the most, and not evenly.  The water and water plus additives expanded slightly.

Conclusion: The pop expanding might be enough to cause the can to pop open.  We didn’t know why the water didn’t seem to expand very much.  We didn’t know why it might or might not spray or “explode” out of the can.

Luckily when our resident scientist came home from work, he was able to point out a bit more information.  For one thing, we should have put lids on the glasses so no water could evaporate into gas.  Also, the carbonation of the pop might in fact have something to do with it.

Further internet searching after our experiment was over revealed that if the freezing water takes up more space, not all the pop in the can may be frozen yet, causing some to spray out of the can when it is suddenly popped open.  An “ask a scientist” feature at the DOE website points to the carbonation being a factor as well: “Soda pop is a super saturated solution of carbon dioxide (plus other ingredients). When it is frozen the CO2 and other dissolved substances are excluded from the ice that forms. So one is confining the CO2 to a smaller and smaller volume of “head space” in the bottle or can. If the bottle or can is not strong enough, the CO2 pressure will rupture the container.

Apparently this may be wrong information: This page at ehow and this site don’t agree with what the “Ask a Scientist” website suggested…I guess we still have more reading to do to learn exactly what is going on with these pop cans! 🙂

Fascinating stuff!  I’m linking up with Science Sunday @ Adventures in Mommydom!

Science Sunday

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2 Responses to “Why Do Pop Cans Explode in the Freezer? (And Other Science Fun)”

  1. Amy @ Hope Is the Word Says:

    This is great, Kirsten!

  2. […] Discoveries shared why sodas explode in the freezer, it was a fun read and I know I’ve left a soda or two in too long while trying to instantly […]


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