Unit 1Lesson 2 The Water Cycle
What Goes Up …
What is the water cycle?
•The movement of water between the atmosphere, land, ocean, and living things makes up the water cycle.
•Rain, snow, and hail fall on the oceans and land. On land, ice and water flow downhill.
•Water vapor moves upward and is carried great distances by the wind. The wind also creates ocean currents.
How does water change state?
•Water on Earth is found as a liquid, solid, and gas.
•Water absorbs energy from its surroundings as it melts from solid to liquid.
•Water also absorbs energy as it evaporates from liquid to gas, or when it sublimates from solid to gas.
•Water releases energy to its surroundings when it condenses from gas to liquid.
•Water also releases energy when it freezes from liquid to solid or deposits from gas to solid.
•No water is lost during these changes of state.
How does water reach the atmosphere?
•Water reaches the atmosphere as water vapor through evaporation, transpiration, and sublimation.
•Evaporationoccurs when liquid water changes to water vapor.
•Most of the water vapor evaporates from Earth’s oceans.
•Transpirationis the release of water vapor into the atmosphere by plants.
•Sublimationis when solid water changes directly to water vapor without first becoming a liquid.
•Sublimation can occur when dry air blows over ice or snow, where it is very cold and the pressure is low.
•Identify each process as evaporation, sublimation, or transpiration.
What happens to water in the atmosphere?
•Condensationis the change of state from gas to liquid. It can occur in the air as clouds, fog, or mist, or on the ground as dew.
•Precipitationis any form of water that falls to Earth from clouds.
•Rain, snow, and hail are common forms of precipitation.
How does water move on land and in the oceans?
•Streams, rivers, and the water that flows over land are types of runoff. Runoff flows downhill.
•Some of the water on land seeps into the ground. This process is called infiltration.
Once undergound, the water is called groundwater. Groundwater also flows downhill.
•Glaciers, which may be called “rivers of ice,” flow downhill and sometimes flow to the ocean, where pieces may break off.
•Winds move ocean water on the surface in great currents over long distances.
•Cold or salty water will sink in the ocean, forming deep ocean currents that move large amounts of water.
Water Works
What does the water cycle transport?
•The water cycle moves energy and matter.
•Energy is transported by changes in state and by the movement of water from place to place.
•Matter is transported all around the world by ocean currents, rivers, and glaciers.
•Identify the processes in the water cycle.