2 cups of water, 1 tablespoon of salt, A refrigerator to freeze.
Take 1 cup of water and add salt. Then put both the cups of water in the refrigerator and freeze. Check from time to time to find out which freezes first.
* Salt decreases the freezing temperature of the water. * This is the reason why lakes and streams freeze in very cold temperatures, but an ocean containing salt water is always free flowing.
The cup of salt water freezes later than the cup of plain water.