2-2 Water P H
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2-2 Water P H

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2-2 Water P H 2-2 Water P H Presentation Transcript

  • 2.2 Properties of Water Pages 40 - 43
  • Goal 1: Explain the polarity of water molecules
    • Polar molecule
      • A molecule with slightly charged “poles”
      • One end is slightly positive
      • Other end slightly negative
      • Due to uneven distribution of electrons
    • Oxygen end
      • Many protons has stronger hold on electrons
      • Slight Negative charge
    • Hydrogen ends
      • “ naked” protons
      • Slight Positive charge
    Image: PD on wikipedia http://commons.wikimedia.org/wiki/Image:H2O_(water_molecule).jpg
    • Polarity results in Hydrogen bonds forming
      • Type of Van der Waals force
      • Weak attraction
      • Between hydrogen and a negative atom
    • Hydrogen bonding between water molecules
    Image credit: Qwerter, Michal Manas on Wikipedia commons http://en.wikipedia.org/wiki/Image:3D_model_hydrogen_bonds_in_water.jpg
  • Image credit: placbo on Flickr
    • Cohesion
      • Attraction between SAME molecules
      • i.e. water & water
  • Image credit: Mr. Greenjeans on Flickr http://www.flickr.com/photos/gaylon/298648625/
    • Adhesion
      • Attraction between different molecules
      • Plants use adhesion and capillary action in Xylem for water transport
  • Image credit: ShutterSparks on Flickr http://www.flickr.com/photos/shuttersparks/1413258875/
  • Image credit: Luc Viatour on wikipedia commons http://en.wikipedia.org/wiki/Image:Dew_on_a_Equisetum_fluviatile_Luc_Viatour.jpg
    • An excellent example of cohesion and adhesion
    • Capillary action
      • Cohesion
      • Adhesion
      • (evaporation)
    Image credits: http://www.sciencebuddies.org/science-fair-projects/project_ideas/PlantBio_p033.shtml
  • Goal 2: Distinguish between a solution and a suspension
  • Solution
    • Solute = substance that dissolves
    • Solvent = substance in which solute dissolves
    Image credit: Chris 73 on wikipedia http://en.wikipedia.org/wiki/Image:SaltInWaterSolutionLiquid.jpg
    • Solution characteristics
      • Dissolving
      • Compounds separate
      • Solute does NOT settle out
    Image credit: hundrednorth on Flickr http://www.flickr.com/photos/100n30th/4821481/
    • Suspension
      • No dissolving / separation of compounds
      • Settling occurs
    Image credit: consumatron on Flickr http://www.flickr.com/photos/consumatron/2514611795/
  • Goal 3: Explain acidic and basic solutions
    • Hydrogen Ions and hydroxide ions
      • Water molecule will separate to form ions
      • pH scale measures H+ ion presence
      • Copy equation on pg 42 to see why a water molecule forms one of each ion.
    • Hydrogen (H + ) ions are associated with acids
      • Recognize acids by the “ H ” found in the compound (often found at beginning or end of chemical formula)
    H 2 SO 4 H NO 3 H 3 PO 4 H Cl
    • Hydroxide ions (OH - ) are associated with bases
      • Recognize some bases by the “ OH ” found in the compound (other bases steal a “H + ” from water and leave behind an “OH - ” group)
    K OH Ba( OH ) 2 Na OH Ca( OH ) 2
    • Acids
      • Release hydrogen ions H + in solution
      • Concentration of H + is high
      • pH 0 – 7
      • acidic
    Image credit: Lou FCD on Flickr http://www.flickr.com/photos/loufcd/2870399185/
    • Bases
      • Produces OH - in solution
      • Less H + ions than pure water
      • pH 7- 14
      • basic
    Image credit: Lou FCD on Flickr http://www.flickr.com/photos/loufcd/2870399185/
  • Concentration of H + ions changes by powers of 10 pH =1 has 10x more than pH = 2 pH = 1 has 100x more than pH = 3 More  Less 1 2 3 4 5 6 7 8 9 10 11 12 13 14
    • Buffers
      • Weak acid or base
      • Neutralizes strong acids or bases
      • Prevents sudden changes in pH