Describe the distribution of Earth's water, including that only about 3 percent is fresh water and most of that is not easily accessible.
Earth is sometimes called the water planet, and oceans do cover most of its surface. Almost all of that water, about 97 percent, is salt water in the oceans, which people and land plants cannot drink or use for farming without special, expensive treatment. Only about 3 percent of Earth's water is fresh water.
Even that small 3 percent is not all easy to use. Most fresh water is locked up in ice caps and glaciers, or is deep underground as groundwater that is hard to reach. Only a tiny sliver of Earth's total water, well under 1 percent of all water on the planet, is in the lakes, rivers, and shallow groundwater that people actually rely on every day.
Mastery looks like: They can state that about 97 percent of Earth's water is ocean salt water and explain why most of the remaining fresh water is not easily accessible.
Common stumbles: Thinking most of Earth's water is fresh water; assuming all fresh water is equally easy to access, ignoring ice and deep groundwater.