BACKGROUND:

Water is our most common natural resource.  It is essential to the biology and chemistry of all living things, it plays a major role in shaping the earth and is an active agent in many physical reactions.  It is important to most life to keep it clean.  There is plenty of water on Earth, but 97% of this water is saline (contains dissolved salts).  Only 3% is fresh and about two thirds of that amount is locked up in polar  ice caps and glaciers; about one third (1%) can be found as ground water, lakes, and in the  atmosphere.

Water exists in three states of matter including  solid (ice), liquid (water), and gas (vapor) at normal  conditions.  Water is a colorless, odorless, tasteless liquid with a melting point of  zero degrees centigrade and a boiling point of 100 degrees centigrade.  

Water is cleaned as it passes through nature’s water cycle.  When water evaporates to the gaseous phase, it leaves the dissolved impurities behind.  Water can also be cleaned through other natural ways.  Overtime, civilization have developed ways in which they can also clean water by taking advantage of part of the natural water cycle. 

PROCEDURE:

1. Water is important to our lives.  Discuss with your students some of the reasons why water is necessary to humans and then write these reasons on the board.  Hopefully, your students should come up with the following reasons:  drinking, for travel, watering plants, and for cleaning.  Discuss the properties of water with your students.
     
2. It is important that you review how the water cycle functions.  After you review, see if the students can derive the cycle by themselves by using the worksheet.   Have the students generate a cycle on the board by having each student add a component to the cycle until the entire water cycle is drawn on the board. 
        
3. Use the following definitions to help students create a water cycle using the worksheet. 

1. evaporation - the changing of liquid to water vapor
2. condensation -  the changing of water vapor to a liquid
3. cloud - a visible  mass of particles of water or ice in the form of fog, mist, or haze, suspended at a considerable height in the air
4. precipitation - forms of water vapor that are heavy enough to fall to the Earth's surface such as rain, snow, sleet, hail, and fog
5. infiltration - the process by which water seeps into the soil and become groundwater
6. spring - a source of water from the ground
7. marsh - a parcel of soft wet land, that can be either salt or fresh water
8. artisan water - underground water trapped under pressure in a porous layer between non-porous rock layers
9. water table - the level below which the ground is saturated with water
10. lake - a body of water larger than a pond and too deep in parts for rooted plants to live
11. river - a natural stream of water larger than a creek and emptying into an ocean, lake, or  another river
12. ocean - the bodies of salt water that cover nearly three fourths of the surface of the Earth 
13. groundwater - water found below the surface of the Earth
14. runoff - water that flows on the surface or through the ground into streams, rivers, lakes and  oceans
15. transpiration - the evaporation of water from the leaves of plants 

[Dictionary] 
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