Water Cycle - Water (2)
Post Lab

  • Analyzing the water cycle.  
  • Exploring how water moves on the surface of the Earth.


  • condensation
  • evaporation
  • precipitation
  • water vapor

Students define evaporation, precipitation, and condensation.


The Earth is made up of both land and water.  When water is heated it changes from  liquid to the gas (water vapor).  This process is called evaporation.  When water vapor is cooled, the gas will go through condensation (change back to liquid form.)  When the drops become large they will precipitate as rain, snow, sleet, or hail. 

We can see water vapor condensing when we watch clouds.  A cloud is nothing more than water vapor that has starting to condensate back to a liquid form.  A cloud is made of extremely tiny drops of water which can remain suspended in the air.  As a cloud grows, and more and more water condense in the same place, the cloud droplets get larger.  Eventually, these cloud droplets will be too large to remain in the air.  The cloud is then said to be saturated.  A saturated cloud will usually precipitate its excess water, or cause it to fall.  This is how it rains or snows.  Moisture falling from clouds is called precipitation.

The amount of the gaseous water vapor that is in the air tells us the relative humidity of the air.  Humidity is a measure of how moist or dry feeling the air is.  When the air is warm, it can hold more water vapor than when it is cold.  When the humidity is high, it is very difficult to dry off after swimming, since there is so much moisture already in the air, it is not easy for more to evaporate.  When the humidity is low, dry air easily evaporates water. 

The cycle of evaporation, condensation, and precipitation of water is called the water or hydrologic cycle.   Since clouds move across the sky, the precipitation does not usually fall in the same place that the water came from.  This is how the earth spreads water across land areas and allow us to live in so many different areas.


  1. Discuss the water cycle.  Make sure you explain the vocabulary by pointing out their position in the water cycle. Discuss with students the different types of condensation, evaporation, and precipitation.  Condensation is the process by which gases become liquid.  Water vapor in the air condenses into tiny drops.  Examples include fog and clouds.  Precipitation is water  which condenses from water vapor.  Precipitation falls to the Earth as rain, snow, sleet, and hail.  Evaporation is the process by which liquid becomes gas.  For example, vapors that rise from the ground on a hot day or when a puddle dries after a rainstorm.  Students may confuse smoke with clouds.  Smoke consists of  particles of substances like oil, wood, coal, but not water.  Clouds, fog, and water vapor are exclusively water. 

  1. Give the students the worksheet and have them define each of the terms after they read or sing Drippy the Hippie.  The pictures should give them “clues” on how to define each of the terms.

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