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WATER & pH
Fun Facts• 50-95% of weight of living things• Only common substance that exists in solid,  liquid and gas forms• If earth ...
Special Properties• Cohesion/ Adhesion• High surface tension• High specific heat  – required to heat 1g of water 1 degree ...
Hydrogen bonds between water molecules
Water transport in plantsCOHESION & ADHESION
Walking on waterHIGH SURFACE TENSION: RESULT OF H-BONDS
Evaporative cooling
The structure of ice
The structure of iceICE FLOATS BECAUSE IT IS LESS DENSE
Ice, water, and steamIce              Water             Steam  WATER IS MOST DENSE AT 4 DEGREES C
Ice floats and frozen benzene sinks
Floating ice and the fitness of the environment
A crystal of table salt dissolving in waterWATER DISSOLVESPOLAR AND CHARGEDMOLECULES
A water-soluble protein
Dissociation• Dissociation of water:  – H2O        H+ + OH-• Dissociation of other things:  – Ex: HCl       H+ + Cl-• Acid...
Chemical reaction: hydrogen bond shift
pH• Aqueous solutions @ 25o C  – [H+][OH-] = 10-14  – [ ] = molar concentration• pH = -log [H+]• pOH = -log [OH-]• Ex: neu...
pH• Each step in pH scale  is an order of  magnitude (x10)
The effects of acid precipitation on a forest
Pulp mill
Acid rain damage to statuary, 1908 & 1968
Buffers• Minimize changes in pH  – Accepts H+ in excess  – donates H+ when depleted• Weak acid and corresponding base• Exa...
Water Movement• Water potential –  – Potential energy of water molecules     • gravity, pressure, conc. of solutes, etc.  ...
Water Movement  Water moves across a selectively permeable  membraneFrom a region of:         To a region of:Higher water ...
Question 1    Many mammals control their body    temperature by sweating. Which property    of water is most directly resp...
Question 2   The bonds that are broken when water   vaporizes areA. Ionic bondsB. Bonds between water moleculesC. Bonds be...
Question 3     Which of the following is an example     of a hydrophobic material?A.   PaperB.   Table saltC.   WaxD.   Su...
Question 4     Acid precipitation has lowered the pH of a     particular lake to 4.0. What is the hydrogen     ion concent...
Question 5     What is the hydroxide ion concentration of     the lake described above?A.   10-7 MB.   10-4 MC.   10-10 MD...
Summary• Polarity of water results in H-bonding  – Water’s special properties• Organisms depend on cohesion of water  – Pu...
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Ch.3 water, p h

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Transcript of "Ch.3 water, p h"

  1. 1. WATER & pH
  2. 2. Fun Facts• 50-95% of weight of living things• Only common substance that exists in solid, liquid and gas forms• If earth was smooth, depth of water would be 2.5m• 98% of water is in liquid form – 2% polar, glacial, soil, atmosphere, organisms – Most evaporation is from oceans
  3. 3. Special Properties• Cohesion/ Adhesion• High surface tension• High specific heat – required to heat 1g of water 1 degree C• High boiling point• High heat of vaporization – Heat required to convert 1 g of water to water vapor – 580 cal• Ice floats• Versatile Solvent
  4. 4. Hydrogen bonds between water molecules
  5. 5. Water transport in plantsCOHESION & ADHESION
  6. 6. Walking on waterHIGH SURFACE TENSION: RESULT OF H-BONDS
  7. 7. Evaporative cooling
  8. 8. The structure of ice
  9. 9. The structure of iceICE FLOATS BECAUSE IT IS LESS DENSE
  10. 10. Ice, water, and steamIce Water Steam WATER IS MOST DENSE AT 4 DEGREES C
  11. 11. Ice floats and frozen benzene sinks
  12. 12. Floating ice and the fitness of the environment
  13. 13. A crystal of table salt dissolving in waterWATER DISSOLVESPOLAR AND CHARGEDMOLECULES
  14. 14. A water-soluble protein
  15. 15. Dissociation• Dissociation of water: – H2O H+ + OH-• Dissociation of other things: – Ex: HCl H+ + Cl-• Acids yield H+ ions• Bases yield OH- ions
  16. 16. Chemical reaction: hydrogen bond shift
  17. 17. pH• Aqueous solutions @ 25o C – [H+][OH-] = 10-14 – [ ] = molar concentration• pH = -log [H+]• pOH = -log [OH-]• Ex: neutral solution, [H+] = 10-7 – pH = -log [10-7] = -(-7) = 7
  18. 18. pH• Each step in pH scale is an order of magnitude (x10)
  19. 19. The effects of acid precipitation on a forest
  20. 20. Pulp mill
  21. 21. Acid rain damage to statuary, 1908 & 1968
  22. 22. Buffers• Minimize changes in pH – Accepts H+ in excess – donates H+ when depleted• Weak acid and corresponding base• Example: Rise in pH• H2CO3 HCO3- + H+ Drop in pH
  23. 23. Water Movement• Water potential – – Potential energy of water molecules • gravity, pressure, conc. of solutes, etc. – Movement from a region of greater potential to a region of lower water potential• Osmotic potential – – Movement across a selectively permeable membrane – Determined by measuring the pressure required to stop the osmotic movement of water in the solution
  24. 24. Water Movement Water moves across a selectively permeable membraneFrom a region of: To a region of:Higher water potential Lower water potentialLower solute conc. Higher solute conc.Hypotonic soln. (less Hypertonic soln. (moresolute) solute)Lower osmotic potential Higher osmotic potential
  25. 25. Question 1 Many mammals control their body temperature by sweating. Which property of water is most directly responsible for the ability of sweat to lower body temperature?A. Water’s change in density when it condensesB. Water’s ability to dissolve molecules in the airC. The release of heat by the formation of hydrogen bondsD. The absorption of heat by the breaking of hydrogen bondsE. Water’s high surface tension
  26. 26. Question 2 The bonds that are broken when water vaporizes areA. Ionic bondsB. Bonds between water moleculesC. Bonds between atoms within individual water moleculesD. Polar covalent bondsE. Nonpolar covalent bonds
  27. 27. Question 3 Which of the following is an example of a hydrophobic material?A. PaperB. Table saltC. WaxD. SugarE. Pasta
  28. 28. Question 4 Acid precipitation has lowered the pH of a particular lake to 4.0. What is the hydrogen ion concentration of the lake?A. 4.0 MB. 10-10 MC. 10-4 MD. 104 ME. 4%
  29. 29. Question 5 What is the hydroxide ion concentration of the lake described above?A. 10-7 MB. 10-4 MC. 10-10 MD. 10-14 ME. 10 M
  30. 30. Summary• Polarity of water results in H-bonding – Water’s special properties• Organisms depend on cohesion of water – Pull water up plant vessels – Surface tension• Water moderates temperatures on earth – High specific heat – Evaporative cooling/ high heat of vaporization• Ice floats – Lakes and oceans don’t freeze, life goes on under ice• Water is the solvent of life – Dissolves charged/ polar substances
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