Ralph Rothwell, Jr  , age 12, of Franfurt. Germany,,

How does salt melt ice on the sidewalk?

The freezing point, which is also the melting point, of plain water is 32 degrees Fahrenheit, When salt is dissolved in the water, the solution has a lower freezing point 

A solution of salt and water may not freeze solid until the temperature drops to 30, or even 25 degrees  When we spread salt on the sidewalk, it quickly dissolves in the surface ice, which is frozen water, The solution is now salt and water  And unless the weather is very, very cold, it melts and runs away