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Water

VIEWS: 10 PAGES: 27

									     Water

By Señora Ettinger
     Biology
What do you know about
        water?
How many brands of bottled water
    are for sale in the USA?
• ~800 brands
 How much water is on the Earth’s
           surface?
• 97% of the Earth’s water is ocean. Tow
  percent of the earth’s water is frozen in
  glaciers. One percent is fresh water for us
  to use!!
• The average American uses about 100
  gallons of water a day.
• A shower, bathroom faucet, toilet and sink
  use two to five gallons a minute.
     How much water was there
      on Earth when it formed?
• There is the exact amount of water on
  Earth today as when the Earth was
  formed. Water is never totally consumed.
  It always recycles itself, in one form or
  another.
How much water in your brain?
• The average human brain is two thirds
  water
• Trees are also two thirds water.
        Water and elephants
• Elephants can smell water up to 3 miles
  away.
• Also, a dog’s nose is so sensitive that it
  can tell the difference between a tub of
  water with a teaspoon of salt in it.
          Water and frogs…
• If you drop a frog into boiling water it will
  hop straight back out again, but if you put
  it in cold water and heat it slowly the frog
  will boil to death.
How much water in your body?
• Humans are approximately 60% water
  by weight and 75% water by
  volume. As much as 95% of the weight
  of some plants is due to the water they
  contain.
• Water Formula: H2O:
  Hydrogen is held to oxygen by
  hydrogen bonds.
  What are hydrogen bonds?
• Hydrogen bonds: Weak covalent bonds
  specific for hydrogen.
• Water is a polar molecule. This is an
  extremely important property of water.
          What is polarity?
• Polarity: A molecule in which the
  charges are unevenly distributed
  causing the molecule to have
  poles. Ex. A magnet
Why is water a polar molecule?
• Water is a polar molecule because the
  oxygen atom contains 8 protons in its
  nucleus and therefore has a much
  stronger attraction for electrons than does
  the hydrogen atom containing a single
  proton in its nucleus.
       How is water unique?
• Hydrogen Bonding: water molecules are
  attracted to each other forming multiple
  hydrogen bonds between the oxygen of
  one water molecule and the hydrogen of
  another water molecule.
• This unequal distribution of charge causes
  the oxygen end to become negatively
  charged and the hydrogen ends to
  become positively charged.
How can this happen?
Polarity and hydrogen bonding of water
   causes many unique properties:
• 1. Cohesion: An attraction between
  molecules of the same substance
  causing molecules on the surface of
  water to be drawn inward.

• Ex. Surface tension of insects walking
  on water and water forming droplets on
  smooth surfaces.
 Another uniqueness of water:
• 2. Adhesion: An attraction between
  molecules of different substances.
•
• Ex. Capillary action of water being
  drawn up the roots of plants into the
  stems and leaves and the capillary
  action of water being drawn up a small
  glass tube.
     Water can make solutions:
•    Solutions: Formed by the polar
    attraction of water between ionic and
    other polar molecules. Water is able to
    dissolve other polar and ionic
    compounds when mixed by causing the
    ions to break away and surrounding
    them.
  4. Suspensions: Some materials do not
• dissolve in water when mixed but can
  separate into small pieces that do not
            always settle out.

  Ex. Blood which contains water and
  many cells and other molecules and
             sugar water.
      Another characteristic:
• 5. High Boiling Point: Water will boil at
  100oC or 212oF
• Solvent: Substance in which a solute is
  dissolved to make a solution
• Solute: substance that is dissolved in a
  mixture
• Acids: a substance that releases hydrogen
  ions H+ in solution
• Bases: a compound that releases
  hydroxide ions HO- in solution
• Neutralization Reaction: chemical reaction
  that occurs when hydrogen ions of a
  strong acid react with the hydroxide ions of
  a strong base to form water and a salt.
• PH scale: indicates the relative
  concentrations of these two ions (H+ &
  OH-)
• Suspension: mixture containing un-dissolved
  particles distributed within a solid, liquid, or gas.
• Inorganic Compounds: Usually compounds that
  do not contain carbon
• Organic Compounds: carbon containing
  compounds
• Polymerization: process by which large
  compounds are constructed by joining smaller
  compounds
• Monomers: a small molecule that may
  become chemically bonded to other
  monomers to form a polymer.
• Polymer: large compounds formed by
  combinations of monomers
• Macromolecules: large polymers

								
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