* 3 cups of water * 3 different colored cups * Salt * Refrigerator to freeze
Take 1 cup of water and add a pinch of salt in it, then add ½ teaspoon salt in the other cup and 1 teaspoon salt in the last cup of water. Mark the cups indicating amount of salt put in each cup and put all of them in the freezer to freeze. Note the time taken by each of the water to become ice.
The cup of water having a pinch of salt freezes first followed by the cup with ½ teaspoon of salt and then the cup of water that has 1 teaspoon of salt. So freezing point decreases with the increase in amount of salt.
* The increase in proportion of salt brings down the freezing point of water. * Hence oceans and seas that contain more salt never freeze.