See if you can lift an ice cube with just a piece of string.
Time: 1 minute set-up and a few minutes experimenting.
- ice cubes
- a piece of string or twine or yarn
- a plate
- table salt
- Lay the middle section of moistened string on top of the ice-cube
- Sprinkle salt on the string and top of the cube
- wait about 30 seconds
- carefully lift the string
- What did you observe?
- What do you think is happening?
- Did the ice cube stick to the string?
- Where you able to lift the ice cube by lifting the string?
Salt lowers the freezing point of water. In other words, salt melts ice. By adding salt to the top of the ice cube, the water melts and the string gets mixed in with the water. If you wait, the water will eventually refreeze and freeze the string into the ice. Can you think of a common every day scenario (in the winter time) where it would be useful to put salt on ice.
- Try using more or less salt
- Try using sugar or pepper or other substances? Do they do the same thing?
- Does the type of string matter?
- Try it by putting the ice cube in a full glass of water.