A project with salt water and ice
Quatr.us answers questions

Salt Water and Ice

Salt Truck
A salt truck spreading salt on the road

You can easily see that salty water freezes at a different temperature than fresh water. If you live somewhere where it gets cold in the winter, you probably already know that you put salt on the sidewalk to melt the ice so people can walk on it.

If you don't, though, you can test this out by filling two cups with water and putting a spoonful or two of salt in one of them. Stir, and put both cups in the freezer. How long does it take each of them to freeze? Does it make a difference if there is even more salt in the water?

The reason water takes longer to freeze when it is salty is that the salt molecules get in the way of the water molecules when they try to form regular ice crystals.

More about salt
Salt in human history

Bibliography and further reading about salt:

More about sedimentary rocks
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Professor Carr

Karen Eva Carr, PhD.
Assoc. Professor Emerita, History
Portland State University

Professor Carr holds a B.A. with high honors from Cornell University in classics and archaeology, and her M.A. and PhD. from the University of Michigan in Classical Art and Archaeology. She has excavated in Scotland, Cyprus, Greece, Israel, and Tunisia, and she has been teaching history to university students for a very long time.

Professor Carr's PSU page

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