MadSci Network: Earth Sciences
Query:

Re: Why does a icecube melt faster in fresh water then salt water?

Date: Mon Feb 26 18:03:43 2001
Posted By: Allan Harvey, Staff,National Institute of Standards and Technology
Area of science: Earth Sciences
ID: 982721911.Es
Message:

This seems to be a pretty common question -- you can find in the MadSci archives a lot of questions and answers related to melting, including one that is almost exactly the question you asked. So you can start by taking a look at these questions (and their answers):

/posts/archives/jul99/932797516.Ch.q.html
/posts/archives/nov2000/975640816.Ch.q.html
/posts/archives/aug99/934466473.Ph.q.html

As with many things, there may not be "the answer," as several factors are involved.

One other factor that comes to my mind besides what is written in those answers is that salt water is more dense than pure water. This will give the ice greater buoyancy so that it will float higher. This will put more of the ice in contact with the air (instead of with the liquid), which will slow down the rate of heat transfer and therefore the rate of melting. That will probably be a small effect, but I wouldn't expect much difference between salt water and pure water anyway.

Finally, I should mention that it is important in your experimental design to have identical conditions to support your conclusions. That means starting with the water and salt water at the same temperature, having the same amount of water and salt water in identical containers, and having the ice cube be the same size in each case. For that last one, you can average out the variations in ice cube sizes by repeating the experiment many times.

Allan Harvey
"Don't blame the government for what I say, or vice-versa."


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