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Water

Water. A bit about water . . . . I. Water and hydrogen bonding II. Properties of water III. Acids and bases. Water and hydrogen bonding. Polar covalent bond : bond in which electrons are shared unequally. Hydrogen bonds. Properties of water. Cohesion Temperature stabilizing capacity

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Water

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  1. Water

  2. A bit about water . . . . I. Water and hydrogen bonding II. Properties of water III. Acids and bases

  3. Water and hydrogen bonding • Polar covalent bond : bond in which electrons are shared unequally.

  4. Hydrogen bonds

  5. Properties of water • Cohesion • Temperature stabilizing capacity • Insulation of bodies of water by ice • Solvent properties

  6. Cohesiveness Due to H-bonding, water is highly cohesive. Cohesiveness accounts for high surface tension

  7. Water-conducting cells 100 µm Cohesiveness

  8. Water and Temperature

  9. Temperature stabilizing capacity Specific heat - amount of energy a substance must absorb per gram to increase temp 1 degree C

  10. Temperature stabilizing capacity Specific heat - amount of energy a substance must absorb per gram to increase temp 1 degree C specific heat of water is 1 cal/gram

  11. Specific heat of water is higher than most other liquids because of extensive H-bonding

  12. Water and temperature

  13. Effect of a large body of water on temperature

  14. High specific heat buffers against temperature increases

  15. High specific heat of water Important in context of cell biology because cells release large amounts of energy during metabolic reactions. Release of heat would pose overheating problem were it not for high specific heat of water

  16. Evaporative Cooling

  17. Ice Floats

  18. Solvent of Life

  19. Solvent properties Water is an excellent solvent for biological purposes because of its ability to dissolve great variety of solutes.

  20. Hydrophilic Hydrophobic

  21. Solvent properties • Hydrophilic: polar molecules that dissolve readily in water; sugars, organic acids, some amino acids. • Hydrophobic: non-polar molecules that are not very soluble in water. lipids, some proteins

  22. Water is a polar solvent

  23. Water Disassociates H+ OH -

  24. Acids and bases • pH scale expresses hydrogen ion (H+) concentration in a solution. • logarithmic scale ranging from 0-14 • neutral = 7

  25. pH • Acids dissociate in water to increase the concentration of H+. • pH values lower than 7 • Bases combine with H+ ions when dissolved in water, thus decreasing H+ concentration. • pH values above 7

  26. pH scale more H+ more OH-

  27. 9 • Buffers act as a reservoir for hydrogen ions, donating or removing them from solution as necessary. 8 7 6 Buffering range 5 pH 4 3 2 1 0 0 1 2 3 4 5 Amount of base added

  28. Acid Precipitation Coal

  29. Damage from Acid Rain

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