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When salt is added to fresh Ice water to cool a six-pack of beer, it does it much more quicker. I know that salt water has a lower freezing point than fresh water, but if the fresh water was at near 0 deg C before the salt was added, then it got below 0C with the salt. Where did the water get it's extra "cool" if the ice is only at 0C? In other words, how was that the ice salt-water get below 0C when all it had was ice thats at 0C?
- Omar (age 31)
As you say, salt lowers the melting point of ice. So adding the salt to the 0 °C ice-water melts some of the ice. But liquid water has higher bond energy than solid ice, because in ice the water-water bonds settle into lower energy arrangements. Where does the energy to mess up those bonds come from? It comes from all the thermal jiggling energy of the water, ice, and beer. Reducing that thermal jiggling is the same thing as lowering the temperature.
(published on 07/12/12)
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