Ice Cube Rope - Sick Science!

1. Take an ice cube out of your freezer and drop that chilly block in a glass of water.
2. The ice cube floats! But now you've got to get the ice cube out of the water… without grabbing it. All you can use is a length of string!
3. Try laying the string across the top of the ice cube. Let the string sit there for a few seconds and try to lift the ice cube out of the water. Did it work?
4. Now lay the string across the top of the ice cube again. This time, sprinkle some Kosher salt onto and around the string as it lays on the ice cube.
5. Again, wait a few seconds with the string sitting atop the ice cube.
6. Carefully lift the string. Did it work this time? (If it didn't, try adding some more salt and try it again.)

How does it work?

Water is a very fickle material. The introduction of a contaminant will instantaneously drop the freezing point below 32°. Crazy, right? It's true. You witnessed it with the experiment you just did. When you added the salt, you introduced a contaminant to the frozen water of the ice. The ice then melted and refroze around the string as the "contaminated" H₂O molecules were cooled by the surrounding molecules.

Additional Info

• What do you think would happen if you tried to freeze salt water? 
• What about trying to boil salt water? 
• What conclusions can you draw about the introduction of contaminants to water?