- Water exists on Earth in all three phases: solid, liquid and gas.
- The water cycle moves water from the hydrosphere to the atmosphere to the land and
back again. - The major processes of the water cycle include evaporation and transpiration, conden-
sation, precipitation and return to the oceans via runoff and groundwater supplies.
Review Questions
- About what percent of the Earth’s water is fresh water?
- About what percent of all of Earth’s water is found in groundwater, streams, lakes,
and rivers? - Explain the following statement: The water on other planets is present in a different
form than on Earth. - What powers the water cycle?
- In what state would water be found at 130oC? What state would water be at -45oC?
- Define the words condensation and evaporation.
- Summarize the water cycle.
- Why do you think the atmosphere is so important to the water cycle?
- Suppose the sun grew much stronger in intensity. How would this affect the water
cycle?
Further Reading / Supplemental Links
Vocabulary
aquifer A layer of rock, sand, or gravel that holds large amounts of groundwater. Humans
often use aquifers as sources of freshwater.
condense To turn from a gas to a liquid.
freshwater Water with a low concentration of salts, which can be consumed and used by
humans.
groundwater Water that is found beneath the Earth’s surface, between soil or rock par-
ticles.
precipitation Water that falls to the Earth from the sky. Precipitation usually takes the
form of rain, but can also occur as snow, sleet, or hail.