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Water, Hydrogen Bonds, and the Hydrologic Cycle


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Water, Hydrogen Bonds, and the Hydrologic Cycle

  1. 1. Water, Hydrogen Bonds, and the Hydrologic Cycle (The Wonderful World of Water) By: Brad & Luke
  2. 2. Structure of Water <ul><li>Covalent bonds link two hydrogen atoms to one oxygen atom. </li></ul><ul><li>Neutral in charge (protons=electrons). </li></ul><ul><li>Molecule is polar. </li></ul><ul><li>Hydrogen bonds cause molecules to cling together in the liquid form. </li></ul>
  3. 3. Properties of Water <ul><li>Density of water is 1g/ml. </li></ul><ul><li>Boiling point – 100 ° C </li></ul><ul><li>Freezing point – 0 ° C </li></ul><ul><li>Water is self-ionizing, that is, there is a tendency for a hydrogen atom to jump from one oxygen atom to another forming OH - and H 3 O + . In any volume of water there is a constant number of molecules that are ionized. </li></ul>
  4. 4. Resistance to Temperature Change <ul><li>The high specific heat of water is caused by hydrogen bonding. </li></ul><ul><li>Because so much energy is required to break the hydrogen bonds, water resists temperature change. This is important because a number of biological processes can occur only within a narrow temperature range. </li></ul>
  5. 5. Water as a Solvent <ul><li>Many important molecules in living things, especially sugars, have regions of partial positive and negative charge. </li></ul><ul><li>These molecules attract water molecules and also dissolve in water. Such molecules are called hydrophilic . </li></ul><ul><li>Molecules that do not have polar regions, such as fats, tend to be insoluble. They are said to be hydrophobic . </li></ul>
  6. 7. Ice <ul><li>In most liquids the density of the liquid increases as the temperature drops. </li></ul><ul><li>However, ice is less dense than water. </li></ul><ul><li>This is because at 4 °C the water molecules are so close that they are all able to form hydrogen bonds with four other molecules. Because of the shape of the molecule, it requires the molecules to spread out and form an open latticework structure. </li></ul>
  7. 8. Surface Tension <ul><li>Result of cohesion of water molecules. </li></ul><ul><li>Causes surface to act like a weak elastic skin. </li></ul><ul><li>The stronger the intermolecular force, the greater the surface tension. </li></ul><ul><li>Water has a strong surface tension because of hydrogen bonding. </li></ul>
  8. 9. Hydrogen Bonds <ul><li>An especially strong dipole-dipole force between molecules. </li></ul><ul><li>Not the same as covalent bonds within a molecule. </li></ul><ul><li>Occurs between molecules that have N-H, O-H, or F-H bonds. </li></ul><ul><li>About 10 times stronger than ordinary dipole-dipole forces. </li></ul><ul><li>In liquid water, hydrogen bonds last approximately 1/100,000,000,000 th of a second. </li></ul>
  9. 10. <ul><li>The Hydrologic Cycle is: </li></ul><ul><li>The cycling of water through the earth system. </li></ul><ul><li>Also known as the water cycle. </li></ul>
  10. 11. The Hydrologic Cycle Animation <ul><li>Water evaporates from plants, soil, streams, and the ocean </li></ul><ul><li>It then condenses to form clouds </li></ul><ul><li>Water falls to the surface as rain or snow </li></ul><ul><li>Some of the water forms rivers and flows back to the oceans </li></ul><ul><li>Some of it percolates down through the soil to the zone of saturation </li></ul>
  11. 12. Evaporation/Transpiration & Cloud Formation <ul><li>When water is evaporated from the oceans by the sun, it leaves the salt behind. </li></ul><ul><li>In much smaller amounts, water is evaporated from the leaves of plants and the body of organisms. This is called transpiration . </li></ul><ul><li>The water vapor is then carried up into the atmosphere by air currents. </li></ul><ul><li>Clouds are formed when water vapor joins with dust particles in the air. </li></ul>
  12. 13. Precipitation & Surface Runoff <ul><li>When the temperature and pressure are right, larger droplets form, and precipitation occurs. </li></ul><ul><li>Most of the water that falls to earth runs off the surface and into streams, rivers, and lakes. </li></ul><ul><li>Eventually, the water returns to the oceans. </li></ul><ul><li>Some of the water soaks through the ground and either returns to the surface via springs or collects underground as groundwater . </li></ul>
  13. 14. Infiltration / Percolation <ul><li>The process of water penetrating the surface into the soil layer is called infiltration . </li></ul><ul><li>Percolation defines the movement of water through the soil. </li></ul>
  14. 15. Acid Rain <ul><li>Average pH of normal rain is about 5.6 (mildly acidic). </li></ul><ul><li>Potential consequences on biological systems: </li></ul><ul><ul><li>Lower crop yields </li></ul></ul><ul><ul><li>Decreased timber production </li></ul></ul><ul><ul><li>Need for greater amounts of fertilizer </li></ul></ul><ul><ul><li>Loss of important freshwater fishing areas </li></ul></ul><ul><ul><li>Loss of eastern forests </li></ul></ul>
  15. 16. Fun Facts <ul><li>70% of the Earth’s surface is covered with water. </li></ul><ul><li>Volume of water increases approximately 9% when it freezes. </li></ul>
  16. 18. Sources <ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul>