II. Properties of Water

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II. Properties of Water

• Water is the single most abundant
• compound in most living things.
• A. The Water Molecule
• 1. Polarity
• Polar molecule a molecule
• in which the charges are
• unequally distributed.
• -Water is a neutral, bent
• molecule. Its bent shape
• makes the oxygen end
• (pole) slightly negative its
• hydrogen end slightly positive.
• -Water molecules are polar because
• there is an uneven distribution of

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Hydrogen Bonding

• 2. Hydrogen Bonds
• Hydrogen bonding weak
• attraction between polar
• molecules, ex water.
• Is the weakest type
• of bonding.
• -Being polar, water
• molecules are
• attracted to each
• other (hydrogens to
• oxygens).

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Cohesion vs. Adhesion

• -Water is very cohesive.
• Cohesion an attraction
• between molecules of
• the same substance, ex
• spiders on water.
• Adhesion an attraction
• between molecules of different
• substances, ex the meniscus
• of water in a graduated
• cylinder.
• -Adhesion is responsible for
• capillary action (water rising in
• a narrow tube against gravity)
• in plants.

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B. Solutions Suspensions

• -Water is sometimes
• part of a mixture a
• material composed of
• 2 or more elements or
• compounds that are
• physically mixed
• but not chemically
• combined, ex
• salt pepper.

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2 Types of mixtures made with water

• 1. Solutions mixture of 2 or
• more substances in which the molecules of the
  substances
• are evenly distributed.
• -Solutions involve solutes
• a substance that is
• dissolved (salt) solvents
• substances in which the
• solute dissolves (water).
• -Water is the universal solvent.
• 2. Suspensions mixtures of water and
  non-dissolved materials, ex blood.

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C. Acids, Bases, and pH

• pH scale measurement
• system used to indicate the
• concentration of hydrogen
• ions (H) in solution it
• ranges from 0 to 14.
• -A pH of 7 has an equal
• amount of H OH-
• ions, making it neutral.
• Pure water is neutral.
• -pH below 7 is acidic pH
• above 7 is basic or alkaline.
• Higher pH more basic solution.

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Acids, Bases, and Buffers

• Acid any compound that forms H
• (hydronium) ions in solution, ex stomach
• acid, lemon juice, tomato juice, acid rain, etc.
• -Anything below 7 on the pH scale.
• Base a compound that produces OH
• (hydroxide) ions in solution, ex bleach,
• soap, ammonia, sea water, lye, etc.
• -Anything above 7 on the pH scale.
• Buffers weak acids or bases that
• can react with strong acids or bases to
• prevent sharp, sudden changes in pH.
• - Are used by body to maintain homeostasis
• by keeping chemical reactions pH balanced.