Some of that water is salt water. Some is fresh water. As a group, write down your answer. Tell students that Cup 1 now represents all the salt water in the world. More than 97 percent of the world's water is salty ocean water.
Salt water is too expensive and difficult to process for human use.
We're surrounded by salt water, but for the most part we can't use it. Cup 2 represents 100 percent of the world's fresh water. Less than 3 percent of the world's water is fresh water. Tell each group to write down its response to the small amount of fresh water. The water in one of the cups represents the amount of the kind of water you can't drink and the water in the other cup represents the kind you can .