Freezing in Warm Air

I took a bottle of soda out of the freezer today, and looked at it. Not frozen. I opened it, and was surprised to find that a minute later, there was a chunk of soda-ice floating on top. Somehow, the soda had frozen after I took it out of its cold environment and into a warm one.

This didn’t happen because of the temperature of the room. Instead, it happened because I opened the bottle. When sealed, the bottle is under higher pressure. If you put ice under pressure it will try to take up less space, and since water is more dense than ice (as you can test by observing that ice floats), high pressure melts ice. Once I released the pressure, the soda, which was below the normal freezing point, froze sitting out on my desk.

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5 Responses to “Freezing in Warm Air”

  1. Ian Says:

    I think the pressure change is less likely to be the culprit here than the possibility that the soda was supercooled when you initially removed it from the freezer. A similar thing happened to me once in a mini-mart: I picked a plastic 1L bottle of some colorless carbonated beverage (I forget exactly what) out of the cooler at the back of the store, noticing as I selected it that about a third of the surrounding bottles were frozen. However, the contents of this particular bottle were definitely still liquid. As I walked up to the register to pay, the plastic bottle slipped out of my grip and fell onto the floor. By the time I picked it up a few seconds later the contents had turned to slush. It still hadn’t frozen completely (and didn’t finish freezing solid), and I assume that’s because the heat released in crystallizing a fraction of the liquid warmed the bottle contents up to the freezing temperature.

  2. Mark Eichenlaub Says:

    Damn, Ian. I was hoping you wouldn’t even read that post and then I could pose it to you as a puzzle this weekend. Now instead I’m going to be reading tonight trying to figure out what supercooling is. Is this related to how crystals form spontaneously out of solution when you scrape on the edge of the Pyrex with a stirring rod?

  3. Mark Eichenlaub Says:

    Okay, definitely not due to pressure change. The internet tells me that water freezes only a fraction of a degree cooler at 2atm than 1.

    As usual for Wikipedia, the supercooling article is a good place to start. Apparently, Coke once created a super-cooled version of Sprite, but nowadays the project has been put on ice.

  4. Seb Says:

    There’s a cool video of superheating water and supercooling beer here:

    Actually there’s tons. Here’s another one:

    (BTW thanks for the refutation on Chad’s post, Mark!)

  5. Mark Eichenlaub Says:

    Cool videos, Seb. Thanks.

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