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Water, Life, Civilization: Why Water?

Water, Life, Civilization: Why Water?. Water: H 2 O. Water: H 2 O. Water and Similar Compounds. H. H. H. H. S. O. Hydrogen Sulfide. Water. H 2 S. H 2 O. Water: H 2 O. Hydrogen Sulfide: H 2 S. Water is the only substance that exists as a gas, solid, and

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Water, Life, Civilization: Why Water?

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  1. Water, Life, Civilization: Why Water?

  2. Water: H2O

  3. Water: H2O

  4. Water and Similar Compounds H H H H S O Hydrogen Sulfide Water H2S H2O

  5. Water: H2O Hydrogen Sulfide: H2S

  6. Water is the only substance that exists as a gas, solid, and liquid at ambient earth temperatures Solid Gas Boiling Point and Freezing Point F.P B.P liquid range Water (H2O) 0oC 100oC 100oC Hydrogen Sulfide (H2S) -84oC -60oC 24oC Hydrogen Selenide (H2Se) -64oC -42oC 22oC Hydrogen Telluride (H2Te) -49oC 2oC 47oC

  7. H2O Two hydrogen atoms One Oxygen atom What makes water so unusual?

  8. Hydrogen: 1 electron (-), 1 proton (+) Oxygen: 8 electrons (-), 8 protons (+) In water, the hydrogens shares their one electron with oxygen, which shares one of its electrons with each hydrogen. This sharing of electrons forms the bond between hydrogen and oxygen atoms to make the water molecule.

  9. H Hydrogen 1 Electron (-) Nucleus 1 Proton (+)

  10. e- e- e- e- e- e- e- e- Oxygen 8 electrons Outer shell 8 protons O The outer shell of electrons determines reactivity

  11. e- e- e- e- e- e- e- e- Oxygen Atoms prefer 8 electrons in the outer shell Outer Shell O

  12. How does oxygen exist in the atmosphere? O2

  13. O O e- e- e- e- e- e- e- e- e- e- e- e- O2 Covalent Bonding Atoms prefer 8 electrons in the outer shell

  14. H H e- e- e- e- e- e- e- e- Water H H O H Bonding of hydrogen to oxygen in a water molecule is called Covalent Bonding

  15. Shared electrons Water Molecule Shared electrons Bond of shared electrons O H H O H H

  16. Water is Unbalanced by Oxygen H H O

  17. e- e- e- e- e- e- Oxygen is “Electron Greedy” Oxygen attracts electrons very strongly O H Oxygen’s pull on electrons is about 50% stronger than hydrogen

  18. e- e- e- e- e- e- e- e- P+ P+ Electrons are negatively charged, protons positive Oxygen is “electron greedy” Oxygen pulls electrons toward itself and away from hydrogen O H H P+ P+ This pulling of electrons toward itself is called “electronegativity”

  19. e- e- e- e- e- e- e- e- P+ P+ Abundant electrons (negative charge) O H H Two protons (+ charge)

  20. More negative charges ( - ) Fewer negative charges

  21. Polarity _ Red = lots of e- Blue = few e- + + + Electric Dipole

  22. Consequences of Polarity

  23. N S Magnets and Polarity Magnetic Dipole

  24. N N S S Polarity Opposite Poles Attract

  25. N N S S Polarity Same Poles Repel

  26. N N S S Polarity http://games.mochiads.com/c/g/polarityfreak/polarityfreak-11-Mochi-Sec.swf

  27. + - Polarity Slight positive charge Electric Dipole Slight negative charge

  28. Bond + + - - Orientation (hydrogen bond) Opposite charges attract each other

  29. Hydrogen Bonding in Water Hydrogen Bonding Gives Water Unusual Stability

  30. Summary Hydrogen and oxygen share electrons to form water The water molecule is electrically unbalanced Oxygen is electron greedy; it is highly electronegative Oxygen draws electrons toward itself and away from hydrogen This creates a slight negative charge near oxygen There is also a slight positive charge near hydrogen The result is a molecule that is polar (+ and – poles) This polarity accounts for electrostatic bonding between water molecules Bonding between water molecules gives water unusual stability.

  31. Effect on Properties Extensive Hydrogen Bonding Allows Water to Exist as a Liquid at Normal Temperatures and across a wide range in temperatures High Boiling and Freezing Points Other Unusual Thermal Properties Unusual Density

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