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Chemical_and_Physical_Properties_of_Water

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					 COVERSMORE THAN 70% OF
 OUR PLANET!!!
 The  most abundant substance on
  earth’s surface.
 Principle component of seawater
 Exists in 3 states:
  › Liquid, Gas (vapor), Solid (ice)
Water  is a polar, covalent
 compound
Extraordinarily stable (does
 not decompose easily!)
This allows for the
 following properties:
 › Cohesion (stick together)
 › Adhesion (stick to others)
 › Surface tension
 › Great dissolving power
› Viscosity changes
  Cold water becomes more
   viscous faster than other liquids.
  In cool water the high viscosity
   means plankton use less energy to
   keep from sinking
  In cool water it takes more energy
   for fish to swim
Most abundant    elements in
 seawater:
 › Hydrogen (H)
 › Oxygen (O)
These 2 make up about
 96.5% of seawater’s mass.
 The  total quantity or concentration
  of all dissolved inorganic solids
 Varies slightly from place to place
 Differences caused by:
  › Evaporation
  › Precipitation
  › River input
  › Depth
 Salinityaverages 34.7 0/00
   › Ranges from 33 0/00 to 38 0/00
 What do we use to measure
  the salinity in our aquariums?
  › Hydrometers measure specific
    gravity (density), so we must use
    the chart and temperature to
    figure out salinity.
 Rainwater flowing over land erodes it
 Wind and waves churn ocean surface of
  that water and atmospheric gases mix and
  dissolve
 Rain falling into ocean carries gases and
  small particles with it.
 Sea water dissolves materials from the
  ocean bottom
 Volcanic discharge
 Hydrothermal vents
 1. The  dissolved ions in the seawater react
  with the ocean floor
 2. Solids precipitate out of water
 3. Salts are continuously removed from the
  ocean by waves washing ashore and
  winds blowing sea spry onto land
 4. Ca and Si are removed by living plants
  and animals; their skeletons sink and are
  buried or washed up on shore
Dynamic Ocean
 › Constantly interacting
  with land, atmosphere,
  and living things
Water is the universal   solvent
Water molecules are
 covalent (not ionic)
 › No electron charge
 › Sharing, but not equally, so
   it’s “partially charged”
    Polar covalent bond
Water Molecule
 NaCl in H2O
 Clusters of water molecules are
  attracted to and surround Na- ions
  and Cl+ ions on the surface of the salt
  crystal
 Polar ends of H2O are attracted to
  them
  › O ends attracted to Cl+
  › H ends attracted to Na-
 Examples:   vital gases (O2, N2)
 › Sufficient amounts do dissolve to sustain
   life
 Examples:   oil, gas
 › These remain in the water as droplets
 › Wind and waves eventually break up
   an oil slick into particles and disperse
   them
 Detergents!
  › Long molecule
  › Ionic end and nonpolar end
      When contact is made with a nonpolar
       compound (oil) it slides its nonpolar end between
       the nonpolar molecules of the oil
      This process allows it to surround small droplets
      The detergent’s ionic end faces outward now and
       attracts water
      Now the oil is surrounded and can be readily
       carried into a solution
 The  ocean is normally more basic
  because all day long algae carry out
  photosynthesis. CO2 is removed from
  the water.
 However, at night more CO2 is added
  to the water than what is being taken
  out, which makes the ocean more
  acidic.
   At about 3000 m and deeper the ocean is
    more acidic
    › Decaying, sinking organic material
      produces CO2
    › No photosynthetic organisms to remove
      it
   Transitions between less acidic and more
    acidic=carbonate compensation depth
     › Water below the CCD can dissolve
     sinking shells
 Photosynthesis   produces O2
 Most reaches surfaces of water and
  is released into atmosphere
 Some stays dissolved in the water
 There is a lot of Oxygen in the top
  1000 meters (decreases steadily as
  you descend)
 At 1000m it drops off drastically= O2
  minimum zone
End of Notes 1!!!!
PHYSICAL PROPERTIES OF
        WATER
 Oceans  absorb tremendous
  amounts of heat!
 Water has the highest heat
  capacity of any ordinary
  substance.
 › Can absorb, or lose, a lot of heat
   and not change temperature much.
 Currents carry water to other
  areas distributing heat energy.
 The ocean waters heat energy
  can be used to melt ice; or it can
  be removed to freeze water.
 › The seas serve as the Earth’s heating
   and cooling system!
 Temperature    is uniform throughout
  the surface layer.
 There is a rapid decrease below
  the base of the surface layer.
  › This area is called the thermocline
    Below the thermocline temperatures
     are fairly constant.
 Temperature     does not change much
  with seasons
 It does change with:
  › Latitude
    High latitudes-cold
    Low latitudes-warm
  › Depth
    Deep-cold! (4°C down to -1.5°C)
 Temperature   affects marine life:
 › Rise in temp.= Rise in photosynthesis
 › Rise in temp.= Rise in metabolic rate
 › Distribution of sea life varies with temp.
 › Warm temp.- Organisms grow faster
 › Warm temp.- Higher reproductive rates
 › Cold temp.- More plant life
    CO2 is more abundant
 D= M/V
 Varies with temperature, salinity,
  and pressure
  › Increased salinity= increased density
  › Decreased temperature= increased
   density
     Exception -4°C: Ice Floats
      is pretty much
 Water
 incompressible
  › Can’t smash it into a smaller space
 Theamount that it can compress
 under its own weight= hydrostatic
 pressure
 Pressure increases 1 atmosphere
 (15lbs/sq. in) for every 10 meters
 (33 feet)
  › Sea level= 1 atm
  › 10m depth- 2 atm
  › 10,000m depth- 1000 atm
 Water   exerts pressure
 › Divers and equipment that goes
   deep down in the ocean must take
   precautions so they are not crushed
 Barotrauma
  › Diver’s lungs and ear drum are
    “squished” on descent.
  › Divers can increase range with SCUBA
    equipment (Self-contained Underwater
    Breathing Apparatus).
  › Divers must exhale consistently while
    ascending to relieve pressure on lungs
 If diving below 60m, one cannot
  use ordinary air- must use a
  special mix- not so much nitrogen,
  if any (it is replaced with helium)
  › At great pressure nitrogen dissolves
    easily into blood and can cause the
    bends
 Decompression    is required after
 most dives.
 › If down to 132m for 1 hr approx. 30
   hrs. of decompression time.
 › A brief dive of 300m requires many
   days!! (and a nifty suit)
 Marine   life is found at all depths, but…
 › Can’t wander up and down
    Take a crab to the ocean depths= squish
    Bring a deep sea viper fish to surface= pop!
     (swim bladder)
 Water’smost
 important
 property… It
 transmits light
  › Without it= No
   photosynthesis
 Iflight hits water at an angle of <90°,
  then refractions occurs.
   › Light slows as it enters water (speed is
     about ¾ of speed in air)
   › Produces rainbows
   › Makes anchor lines look bent
 Limits   to light penetration
  › Ranges from 50m to more than
    100m
  › The region light penetrates= photic
    zone
  › Depth of photic zone depends on
    clarity
 ROY   G BIV
 › Blue light : shorter wavelength; higher
   frequency; penetrates deepest.
 › As it moves through water it is absorbed,
   scattered, and reflected
 › Other colors with longer wavelengths and
   lower energy are absorbed near surface
 Ocean may also appear green, brown,
  or even red!
 Absorption of light:
    › Red      5-10m
    › Orange   10-15m
    › Yellow   15-25m
    › Green    30-50m
    › Blue     60-100
   Vertical Migration
    › Organisms move up and down in water
      column
   Bio-luminescence
    › Living organisms emits light
    › Can you think of any
      organism that
      bio-luminesces?

				
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posted:12/19/2011
language:English
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