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Question

post-21542

Please help, how to answer this question? Thanks. 

Answer

I am not sure it will lower the temperature of the ice. It will lower the freezing point of water but not cause temperature to fall.

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Edited 21-Nov-2016

Actually, the question is not very clear.  It should clearly state when the salt is added.  If the ice is at 0 C at the point when the salt is added, temperature will drop below 0 C, and the ice will melt even the temperature is below 0 C.  This is because adding impurities will lower the melting point of ice.

If we assume that the ice was already below 0 C and the freezing point of saline before the addition of the salt, then (3) will be the answer, since the salt will no lower be able to lower temperature any further.

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Thanks ShockedParent & CKS,

however the answer sheet is (3). Looking at the link below, it does seems that adding salt lowers the melting point of ice, thus (3) is the answer. Do you agree?

http://science.howstuffworks.com/nature/climate-weather/atmospheric/road-salt.htm

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