Then have the students look at a map of surface salinity of the oceans. Think about the surface temperatures of other planets and moons in our solar system. This activity works best as a small group activity, but can be done as a demonstration. As a demonstra-tion, use an overhead projector to record the data for the class. If seawater is unavailable, you can find salt water aquarium mix at any pet store that sells salt water fish.
Isopropyl alcohol works nicely because it contains water.
When the water in the alcohol freezes, it should sink. There are numerous stores that sell dry ice as either chunks or cubes. Ask the salespeople at the store for the best way to handle the dry ice. If you cannot find or do not wish to use dry ice, you can use a salt-ice mixture. In this procedure, you will explore the freezing point of water, including the differences between salt water and fresh water.