Heat is added to melt ice, and heat is given off when water solidifies back into ice. The reaction takes place below our body temperature so we cannot feel it. Thus, they can live under pack ice where salt water is below the freezing temperature of fresh water, but only so long as no ice enters their body. Have students freeze an apple at home and bring it to class to thaw. Place it next to an apple that has not been frozen, and observe it over the next 2-3 days.
Students can respond in their Logbooks or turn in their written explanation at the end of the class.
Salt on roads mixes with ice and water on roads. More heat must be removed from the mixture of ice and water for it to reach its freezing temperature than from pure water. This happens because the molecules have to overcome adhesion of water to the salt molecules in order to arrange themselves in the ice crystal lattice. We put salt on roads because the water remains liquid at a lower temperature. The cream inside the container is not pure water-thus its freezing temperature is lower than the freezing temperature of water.