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Water:

• Most important biological molecule
• Chemical formula H₂O
• 2 Hydrogen molecules covalently bonded to 1 Oxygen Molecule
• Obtains most of it's properties due to it's Polarity and shape.
• Electrons are shared unequally
• Oxygen has a high electronegativity, so it "possesses" the electrons more than hydrogen.
• Hydrogen Atoms are spaced 104.5^O apart. apart.
• Results with the water atom having a (+) charged H side and a (-) charged O side.
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• High polarity results in H₂O's ability to form Hydrogen Bonds.

• Hydrogen bonds are formed by the attraction of the charged portions of the H₂O molecule to the charged portion of other H₂O molecules, Ions, or other polar molecules.

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• This allows for high cohesion properties of water (ability to attract to itself). Allows water to have high specific heat, and heat of vaporization because of the strong attraction of H₂O molecules.

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• Adhesive properties make H₂O a powerful solvent.
• Polar portions of H₂O molecule can "pluck off" Ions from an Ionic crystal lattice.

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• Water Organizes nonpolar molecules.
• Nonpolar molecules are hydrophobic (repelled by H₂O)
• Repulsion forces these molecules into particular arrangements.
• Example is the lipid bilayer found in cellular membranes.

• Water disassociates (ionizes) in itself.
• Basis for the pH scale of acid - base measurement.
• Water can disassociate from H₂O to H⁺ (Hydrogen Ion, acid) and OH^- (Hydroxide Ion, base).
• Usually does this for 1/10,000,000 or 1E^-7.
• pH is a measure of this dissociation. According to the following formula: pH = -Log [H⁺]
• Lower pH indicates high H+ concentration - high acidity.
• Higher pH indicates low H⁺ concentration (high OH^- concentration) - High alkalynity.
• A neutral solution has pH=7.

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Mr. Stanley

Last updated: March 11, 2004