Ice Cube Rope – Sick Science!
Have you ever thrown a lasso around a block of ice?
Most normal people won't put effort into trying to catch a solid chunk of ice with a rope. Luckily, we aren't most people… and we certainly are not normal. Steve and his freeze-ologists wondered if it was possible to pick up an ice cube by using a rope. Seems simple enough. But here's the catch… you can't tie the rope around the ice cube! Believe it or not, it is possible!
- Kosher salt
- A length of string
- A glass of water
- An ice cube or two
- Take an ice cube out of your freezer and drop that chilly block in a glass of water.
- 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!
- 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?
- 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.
- Again, wait a few seconds with the string sitting atop the ice cube.
- 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.
- 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?