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WATER

WATER. Just some facts. 70% of the Earth is covered in water Oceans hold 97% of the Earth’s water Freshwater only constitutes 3% Of that freshwater most is trapped in glaciers and ice caps The rest is found in groundwater, lakes, soil moisture, atmospheric moisture, rivers and streams.

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WATER

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  1. WATER

  2. Just some facts • 70% of the Earth is covered in water • Oceans hold 97% of the Earth’s water • Freshwater only constitutes 3% • Of that freshwater most is trapped in glaciers and ice caps • The rest is found in groundwater, lakes, soil moisture, atmospheric moisture, rivers and streams.

  3. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL • Water keeps us alive, moderates climate, sculpts the land, removes and dilutes wastes and pollutants, and moves continually through the hydrologic cycle. • Only about 0.02% of the earth’s water supply is available to us as liquid freshwater.

  4. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL • Comparison of population sizes and shares of the world’s freshwater among the continents. Figure 14-2

  5. Populations and water supply • Human settlements are determined by the availability of freshwater. • high precipitation and small populations equals highest per capita (Iceland, Norway) • Lowest per capita: Low precipitation and highest populations (Egypt, Israel) • In the US freshwater = 500,000 gallons per person per year.

  6. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL • Some precipitation infiltrates the ground and is stored in soil and rock (groundwater). • Water that does not sink into the ground or evaporate into the air runs off (surface runoff) into bodies of water. • The land from which the surface water drains into a body of water is called its watershed or drainage basin.

  7. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL • We currently use more than half of the world’s reliable runoff of surface water and could be using 70-90% by 2025. • About 70% of the water we withdraw from rivers, lakes, and aquifers is not returned to these sources. • Irrigation is the biggest user of water (70%), followed by industries (20%) and cities and residences (10%).

  8. Salinity • The saltiness.

  9. Importance • Leonardo da Vinci said that “Water is the driver of nature.” Without water, the other nutrient cycles would not exist in their present forms, and current forms of life on earth could not exist.

  10. Water H H O

  11. H H Water • A water molecule (H2O), is made up of three atoms --- one oxygen and two hydrogen. O

  12. About 60-90 percent of an organism is water Water Water is called the universal solvent

  13. Water Properties • Polarity • Cohesion • Surface Tension • Adhesion • High Specific Heat • High Vaporization

  14. Water is Polar • In each water molecule, the oxygen atom attracts more than its "fair share" of electrons • The oxygen end “acts” negative • The hydrogen end “acts” positive • Causes the water to be POLAR • However, Water is neutral (equal number of e- and p+) --- Zero Net Charge

  15. Hydrogen Bonds Exist Between Water Molecules • One hydrogen bond is weak , but many hydrogen bonds are strong

  16. Cohesion • Attraction between particles of the same substance (water is attracted to itself) • Results in Surface tension • Produces a surface film on water that allows insects to walk on the surface of water

  17. Cohesion … Helps insects walk across water

  18. Adhesion • Attraction between two different substances. • Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton. • Capillary action-water molecules will “tow” each other along when in a thin glass tube. • Example: transpiration process which plants and trees remove water from the soil, and paper towels soak up water.

  19. Adhesion Causes Capillary Action Which gives water the ability to “climb” structures

  20. Adhesion Also Causes Water to … Attach to a silken spider web Form spheres & hold onto plant leaves

  21. High Specific Heat • Amount of heat needed to raise or lower 1g of a substance 1° C. • Water resists temperature change, both for heating and cooling. • Water can absorb or release large amounts of heat energy with little change in actual temperature.

  22. High Heat of Vaporization • Water's heat of vaporization is 540 cal/g. • In order for water to evaporate, each gram must GAIN 540 calories (temperature doesn’t change --- 100oC). • As water evaporates, it removes a lot of heat with it (cooling effect).

  23. Hydrologic Cycle

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