chemistry question #95

Colin Genade, a 24 year old male from the Internet asks on November 30, 1999,

Q:

I have seen some advertised ice packs that claim to have salt water solution in them and a clicker, which if pushed will cause the water to freeze. How do these work?

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the answer

Barry Shell answered on November 30, 1999, A:

The cooling is caused by an endothermic chemical reaction that absorbs heat. One website identifies the compounds as a combination of ammonium chloride, urea and buffering agents to create the chemical reaction. There may be various other compounds used in other products. I'm not sure if the water will actually freeze, but it will get cold. The salt solution is probably not ordinary salt, but other salts like ammonium chloride or ammonium nitrate.

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