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Can someone explain in both layman's terms and also technically why when I pulled my glass filled with liquid soda from the freezer, the liquid soda quickly froze?

Doesn't this violate the 2nd law of thermodynamics since heat moved away from the glass with soda and to the ambient?

Thanks

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2 Answers 2

up vote 17 down vote accepted

Your soda was in a supercooled state. Being in the freezer, it was at a temperature below its freezing point however it remained as a liquid as the glass was too smooth to allow ice crystals to start to form (in technical terms, the phase transition requires a nucleation site). When you removed it from the freezer, you gave it the disturbance necessary to catalyse the transition from supercooled liquid into a block of ice. No violation of the 2nd law occurred.

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Right, but main reason for the frequent undercooling of botteld drinks is the fact that the liquids are filtered before filling in the bottle. They are just extermely clean. I wonder, whether the carbonic acid in most drinks plays a role? –  Georg Jun 21 '11 at 10:09
    
Excellent answer, Richard. And Georg makes a good point about the bottled water. I remember about 5 years ago, opening my trunk after a very cold night, and removing a case of bottled water. Each and every one was liquid, but turned instantly to a thick slush when shaken. Lots of supercooled fun we had that morning.... –  Vintage Jun 21 '11 at 22:17
    
You can do the same thing with a bottle of beer (the filtration and alcohol make it easier to supercool them). Just give it a whack and you get instant beer-sicle. Tasty treat, great at parties. –  Jim 8 hours ago

Often this reaction can occur simply due to the release of pressure allowing the chemical change to occur. I used to work at a fast food restaurant, and the frozen cola dispenser was always over-pressurised, meaning that new staff would fill the cup with frozen cola, and then panic as it continued to "grow" in the cup. The liquid was also supercooled, and kept expanding in the cup.

Isn't it weird how water is the only molecule (that I know of) that expands when cooled.

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