- Ice Cubes
- Glass of Water
- Food Coloring (optional)
- String or Twine
How to perform the experiment:
- Add half a dozen or so ice cubes to a cup and fill with water.
- Lay the string over an ice cube.
- Sprinkle salt over the string and ice. Wait 30-60 seconds.
- Gently pull the string. The ice should come along with it!
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Water freezes at 32° F. When you add salt to water, it lowers the water’s freezing temperature, meaning that it has to get colder than 32° F to freeze. The salt you sprinkle on the ice cube lowers its freezing temperature and it starts to melt. A little pool of water forms on top of the ice cube and the string sinks into it. As the ice cube melts, it dilutes the salt/water mixture in the little pool. The freezing point will then go back up again. The ice will then refreeze along with the string.