Chapter 3: Water and the Fitness of the Environment

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Chapter 3 Water and the Fitness of the
Environment

• Makes life on Earth possible
• ¾ of Earths surface
• 60- 90 of cells mass
• Cytoplasm and blood are mostly water
• Small, simple molecule
• Very common (occurrence)
• Very uncommon (chemistry)
• Several unique properties know these

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Polar covalent molecule

• 2 hydrogen and 1 oxygen
• Mass of 18
• Strong zones of partial positive and partial
  negative poles
• Cooperates in MANY hydrogen bonds
• Results in emergent properties
• Conditions or traits that appear (emerge) because
  of the structure or relationships between
  components.
• Ex molecules have different properties than
  elements and a forest has different properties
  than a tree.

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Cohesion and Adhesion

• Surface tension
• Cohesion means water sticks to other water
  molecules.. beads
• This helps keep water liquid, the form we need
  most as living organisms (cytoplasm to oceans)
• Adhesion means that water sticks to other
  substances
• Meniscus in graduated cylinder
• Xylem and phloem in plant stems
• Necessary for PHOTOSYNTHESIS

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Moderates temperature

• Heat gt measure of total kinetic energy
• Temperaturegt intensity of heat due to average
  kinetic energy
• Kilocalorie gtfood cal., 1000 calories
• Calorie gt amt of heat required to raise one gram
  of water by one degree Celsius
• Specific heat gt amt of heat that must be gained
  or lost in order to heat or cool one gram of a
  substance by 1 degree Celsius
• Water has relatively high specific heat

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Specific Heat

• Because water has a high specific heat compared
  to other molecules its size
• It take a long time to change temp.
• Lake stays warm in fall
• Ocean temperatures dont vary much
• Body temp stays steady

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Evaporative Cooling

• Heat of vaporization gt quantity of heat required
  to convert 1 gram of substance from liquid to gas
• Evaporation of sweat (water) takes out a lot of
  body heat
• Hottest molecules closest to phase change, lowers
  overall kinetic energy.
• Sweat, drool, pant, large ears, capillaries, etc

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Ice Floats

• Liquid water has H bonds that hold water in a
  very density collection
• Solid water (ice) actually has longer bonds,
  liquid waters bonds are further apart, less
  dense
• Floating ice
• Doesnt overflow
• Acts as insulation
• Allows for bottom to stay liquid
• Lake can melt completely in the summer
• Weather because of cold polar water and warm
  equatorial waters flow and currents

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Solvent of Life

• Solution gthomogenous liquid mixture of two or
  more substances
• Solutegt what is dissolved, solid, smaller amt.
• Solventgt what did the dissolving, liquid, larger
  amt.
• Aqueous solution gt solution where solvent is
  water
• Very common in nature

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Solutions

• Blood is a solution that carries dissolved
  nutrients, oxygen and waste to and from cells
• Cytoplasm ( cytosol ) is a solution that is
  mostly water and is the site of all chemical
  reactions in cells
• Most biochemistry is carried out in aqueous
  solutions

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Solutions cont.

• Hydrophilic gtwater loving
• Hydrophobic gt water fearing
• Molarity gt number of moles per liter of solution
  (mole is atomic mass in grams)
• Be able to calculate molar solutions
• Dissociationgt degree to which a substance
  separates when in solution.
• Water separates into H and OH -
• Acid gt has more H than OH- available
• Base gt has more OH- than H available

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pH

• pH is the negative log of the H concentration
  and is a measure of how much the water has
  dissociated and how much H is available
• Organisms are very sensitive to pH ranges.
• Some acids include gastic acid, lemon juice,
  soda, coffee, rain(6) and urine (6)
• Pure water should be neutral (7)
• Some bases would include sea water (8), blood
  (7.4), Tums, ammonia/bleach and many cleaners

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Acid Precipitation

• Can be in any format (rain or snow)
• Also exists as exhaust and run off
• S and N in atmosphere bond to water creating
  acids
• Changing pH of lakes or oceans is harmful to
  plant and animal life there
• Changing pH of soil changes the charge and
  availability of ions and nutrients that are used
  by plants
• Both can have impacts on food webs and our
  food/water/oxygen supply