Kids who experience winter snowfalls know what happens when salt trucks pour granules over slushy streets. To recreate this scenario, fill two cups with water. Stir a spoonful of salt in one cup. Place both containers inside your freezer. The salt water requires more time to freeze because the salt particles get in the way of the water molecules when they try for form ice crystals. This same principle applies to salt products that are sprinkled over icy sidewalks.
Salt water is denser than fresh water, which explains why swimmers float more easily in the ocean than they do at a swimming pool or lake. Pour water into a pint jar so that your container is three-quarters full. Watch how a raw egg sinks to the bottom. Add a half ounce of salt to your water and stir with a spoon. The same egg now drifts upward because the salt turns the water into a heavier liquid.
A glass of salt water demonstrates that the brine remains even when we cannot see it. Pour a tablespoon of salt into a clear cup, and fill your container about one third full with hot water. Stir until the salt dissolves. Use a permanent marker to draw a line on the clear cup to indicate the water level. Observe the cup daily until the water evaporates. Notice the salt that remains, because the salt returns to its original solid state as the water evaporates.
Convert salt water into fresh water by mixing 1 1/2 tablespoons of salt into 3 cups of water in a bowl. Place an empty cup in the bowl's center. Stretch plastic wrap over your bowl, and place a small stone in the center so that the plastic slopes downward toward your empty cup. Place the bowl in the sun, and watch as condensation droplets gradually form on the plastic. Salt remains at the bottom of the bowl but the water inside the cup is salt-free.