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February 20

I put a six-pack of soda can in a river, which was not frozen

And the liquid in the soda cans froze. How can water, which is above freezing temperature freeze the liquid in the soda cans? Noopolo (talk) 12:56, 20 February 2015 (UTC)[reply]

Are you sure the water was above freezing, not just "still liquid"? The temperature can be as low as the freezing point of even lower without freezing visibly occurring. And water being in motion rather than still also can prevent the physical freezing process. DMacks (talk) 14:03, 20 February 2015 (UTC)[reply]

See also Supercooling, one important thing is that water in the middle of a river will not have nucleation sites that allow crystal formation. SemanticMantis (talk) 14:45, 20 February 2015 (UTC)[reply]

During cold spells, there are often announcements in the news media that people should let their faucets trickle, because the slight motion of the water in the pipes will lower the temperature at which they will freeze. Jc3s5h (talk) 14:47, 20 February 2015 (UTC)[reply]

I think that's just because the water drains out of the pipe before the temperature has a chance to drop below freezing. StuRat (talk) 05:48, 21 February 2015 (UTC)[reply]

It might also be the case that the additional substances in the soda (which render that liquid "not merely water") raise its freezing point above 0C. Also, was the soda frozen before the cans were opened? Carbonated drinks are under greater than atmospheric pressure while sealed, and the sudden drop in pressure when they're opened cases a drop in temperature (see Adiabatic cooling) that can often cause them to suddenly freeze – I've experienced this many times when opening bottles of lemonade that have been in the fridge. {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 14:50, 20 February 2015 (UTC)[reply]

There are many things that can cause freezing-point depression. But I don't know if it is possible to raise the freezing point of water with a small admixture of any substance (I'd welcome suggestions...) Wnt (talk) 15:08, 20 February 2015 (UTC)[reply]

Gelatine or agar :) - no, not really, see Freezing-point depression. Returning to the original question, this webpage: [1] explains how escaping carbon dioxide causes the cold (but not supercooled) soda to partially freeze when the container is opened. --Dr Dima (talk) 23:21, 20 February 2015 (UTC)[reply]

Could it have been an estuary instead of a river ? Those contain saltwater, which has a lower freezing point than water. Note that the mouths of "rivers" are often actually estuaries, as in this illustration: Estuary#Definition. StuRat (talk) 05:48, 21 February 2015 (UTC)[reply]