General%20Chem.%20Review%20and%20Water%20See%20pages%2020-27

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General Chem. Review andWaterSee pages 20-27
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Transfer of Electrons Intra- and Inter-
molecular Eg. NaCl
Sharing of Electrons Intramolecular Eg. CO2, H2O
Weakest intermolecular Between molecules
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• Be sure to read pp.20-25 in your Inquiry Into
  Life text (9th ed.).
• Youll read about Elements, Atoms, Isotopes,
  Molecules, Compounds, Ionic and Covalent Rxns,
  Double and Triple Bonds, and Redox Rxns.
• All of these serve as a rudimentary review of Jr.
  Science, Chem. 11, and Chem. 12.

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Water

• Not considered organic (it is inorganic) because
  it does not contain carbon and hydrogen together.
• The atoms involved are COVALENTLY bonded (ie.
  they share electrons). In fact, the bonds are
  Polar Covalent.
• Polar covalent implies that the sharing is
  slightly uneven, thus creating partial charges.

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• These charges exist as a partial negative charge
  on the oxygen atom and partial positive charges
  on each of the the hydrogen atoms. (See fig. 2.8,
  page 26).
• This polar nature of water molecules allows for
  HYDROGEN BONDING (ie. a positively-charged
  hydrogen atom is electrostatically attracted to a
  negatively-charged oxygen atom from another water
  molecule). See fig. 2.8 again.
• Hydrogen bonds are depicted by dashed lines
  (unlike ionic/covalent bonds lines which are
  solid).
• It takes less energy to break H-bonds (relative
  to ionic/covalent). In fact, often the KE of the
  water molecules breaks the H-bonds.

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• When water is in its liquid form, its hydrogen
  bonds are very fragile, about 5 as strong as
  covalent bonds.
• They form, break, and re-form with great
  frequency due to the Kinetic Energy of the
  molecules
• But, at any instant, a substantial percentage of
  all the water molecules are bonded to their
  neighbours, giving water more structure than most
  other liquids (in fact, the H-bonds keep water a
  liquid at room temp., not a gas).

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Characteristics of Water (Within the Body)

• Regulates Temperature
• Water has a high heat capacity
• This means that water can absorb a huge amount of
  heat before it evaporates and it gives off this
  heat as it cools and nears freezing (but it also
  cools slowly as it holds heat well).
• This ability of water to maintain a steady
  temperature range keeps the body temperature at
  or around 37.1o C.
• Sweating to cool as well.

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Takes a larger amount of energy to raise the
temp. of water (only NH3 is higher)
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• Water is COHESIVE
• Due to hydrogen bonds, water has great COHESION,
  meaning that water molecules that are ahead of
  others in the flow tug the others along to
  allow for a smooth flow.
• Blood is able to flow smoothly and efficiently
  through its vessels due to this cohesion.
• As well, waters cohesion allows molecules/ions
  to be evenly distributed throughout (important in
  blood).
• Cohesion also plays a role in the ability of
  plants to transfer water from their roots to
  their leaves (through xylem vessels against
  gravity).
• Blood 55 plasma 45 blood cells
• Plasma 90 water 10 dissolved substances.
• Therefore, blood is 49.5 water (of course, cells
  are mainly composed of water too!)

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• Water acts as a LUBRICANT (as it is a liquid at
  body temp.)
• Examples
• Saliva is water-based and helps to coat food for
  easier swallowing.
• Synovial fluid in joints for cushioning and
  smooth/efficient movement.
• Tear ducts to produce tears to keep eyes clean.
• Mucus production to lubricate respiratory tract
  and to catch debris/pathogens that enter the
  body.
• Vaginal/penile secretions for natural lubrication
  during intercourse.

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• Acts as a SOLVENT
• Water dissolves polar substances due to its polar
  nature.
• Polar likes polar, so water only dissolves
  polar solutes.
• Examples Na, Cl-, K, Ca2, glucose, amino
  acids, glycerol, etc.
• Sometimes, water is referred to as a universal
  solvent since it can dissolve so many substances.
• This allows plasma to carry useful polar
  materials dissolved in the water that makes it
  up.
• It also increases the efficiency of the chemical
  reactions that occur in a cell as reactions in
  the aqueous phase tend to happen faster.
• Polar Hydrophilic Non-Polar Hydrophobic

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