1. WATER

2. Just some facts 70% of the Earth is covered in water 70% of the Earth is covered in water Oceans hold 97% of the Earth’s water Oceans hold 97% of the Earth’s water Freshwater only constitutes 3% Freshwater only constitutes 3% Of that freshwater most is trapped in glaciers and ice caps 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. 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. 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. 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. 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. Human settlements are determined by the availability of freshwater. high precipitation and small populations equals highest per capita (Iceland, Norway) high precipitation and small populations equals highest per capita (Iceland, Norway) Lowest per capita: Low precipitation and highest populations (Egypt, Israel) Lowest per capita: Low precipitation and highest populations (Egypt, Israel) In the US freshwater = 500,000 gallons per person per year. 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). 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. 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. 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. 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. 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%). Irrigation is the biggest user of water (70%), followed by industries (20%) and cities and residences (10%).

8. Salinity The saltiness. 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. 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.

11. Water A water molecule (H 2 O), is made up of three atoms --- one oxygen and two hydrogen. A water molecule (H 2 O), is made up of three atoms --- one oxygen and two hydrogen. H H O

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

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

14. Water is Polar In each water molecule, the oxygen atom attracts more than its "fair share" of electrons In each water molecule, the oxygen atom attracts more than its "fair share" of electrons The oxygen end “acts” negative The oxygen end “acts” negative The hydrogen end “acts” positive The hydrogen end “acts” positive Causes the water to be POLAR Causes the water to be POLAR However, Water is neutral (equal number of e- and p+) --- Zero Net Charge 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 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) Attraction between particles of the same substance (water is attracted to itself) Results in Surface tension Results in Surface tension Produces a surface film on water that allows insects to walk on the surface of water 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. Attraction between two different substances. Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton. 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. 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. 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 … Form spheres & hold onto plant leaves Attach to a silken spider web

21. High Specific Heat Amount of heat needed to raise or lower 1g of a substance 1° C. Amount of heat needed to raise or lower 1g of a substance 1° C. Water resists temperature change, both for heating and cooling. 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. 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. 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 --- 100 o C). In order for water to evaporate, each gram must GAIN 540 calories (temperature doesn’t change --- 100 o C). As water evaporates, it removes a lot of heat with it (cooling effect). As water evaporates, it removes a lot of heat with it (cooling effect).

23. Hydrologic Cycle