- Glass of water
- Ice cubes
Drop an ice cube in the glass of water. Take the string and dangle the end of it on the ice cube, and then keep it still.
While the string is dangled down onto the ice cube, sprinkle a bit of salt on the ice cube. Set aside for a few minutes. After some time, try to lift the string and observe what happens to the ice cube.
Salt lowers the freezing point of water to below 0 degrees Celsius. When you added salt to the ice cube, the salt lowered the melting point of the ice. The salt is in a thin layer, so it melts a thin layer on top of the ice cube. The water cooled down further and re-froze around the string.