Water

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Water
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An 8 oz. glass of water is composed of
approximately 7,500,000,000,000,000,000,000,000
molecules of H2O.
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Water

• Wherever water is found, there is life
• It is the most common liquid

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Water is Polar

• Atoms of water are covalently bonded
• Polar covalent bonds
• the oxygen is more ELECTRONEGATIVE than the
  hydrogens, so it pulls shared e-s closer to
  itself
• this makes water a DIPOLE

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Water is Polar

• The total charge on a water molecule is neutral
• The oxygen end is slightly negative
• The hydrogen end is slightly positive
• This uneven distribution of charge makes it polar

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Hydrogen Bonding

• The hydrogen
• bond is a weak
• bond that can
• form between any
• slightly positive
• H-atom and any
• slightly negative
• O-atom

• Because water is polar it forms hydrogen bonds

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Hydrogen
Bonding

• Each water molecule can
• form four hydrogen
• bonds
• Taken together,
• hydrogen bonds have considerable strength
• This attraction among water molecules causes some
  of its unusual properties

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Properties of Water
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Water is Adhesive

• Water sticks to other objects
• Meniscus caused by adhesiveness
• Capillary action is
• partially caused by
• waters adhesiveness

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Water is Cohesive

• Water sticks to itself
• Surface Tension
• High Specific Heat

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High Specific Heat

• Water takes a lot of energy to change state
• Much heat is required to break its hydrogen bonds
• Water tends to stay at a constant temperature

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Universal Solvent

• Solution
• uniform mixture of two or more substances
• Solutes dissolve
• in solvents

• Water can dissolve ionic substances
• Water cannot dissolve nonpolar compounds (oils,
  fats, etc.)

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Dissolving Substances
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Water dissolving an ionic compound
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Oil and water dont mixbecause,
sinceoil is non-polar,water molecules are not
attractedto oil moleculeswater molecules are
attracted toeach other
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Ionization of Water

• H2O ? H OH-
• This accounts for the phenomenon of
• pH

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In water at room temperature, there is one H
ion for every 555 million water molecules This
means that the H concentration is 1 X 10-7
moles/liter The pH is 7
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Acids

• Hydrogen donors (H)
• Solution which contains more H ions than OH-
  ions

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Bases

• Hydrogen Acceptor (OH-)
• Solution which contains more OH- ions than H
  ions

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The pH Scale
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(INTERESTING WEBSITE)
http//www.johnkyrk.com/H2O.html
LAST SLIDE HAS AN INTERACTIVE pH scale
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Buffers

• Combinations of H donors and H acceptors
• Tend to combine with H ions to remove them from
  solution
• Resist strong, sudden changes in pH

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Neutralization Reaction