Properties of Water

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Properties of Water

• Section 2-2

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Water an unusual compound

• Covers three fourths of our planet
• Most abundant compound in living things
• Liquid at room temperature
• Expands as it freezes
• Lighter than most gases
• Moderates temperatures by storing heat

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Water H2O
(Chemical formula)

• Covalent bonds hold the molecule together
• Electrons are shared unequally

• Oxygen takes most of the negative charge
• Hydrogen atoms are left slightly positive

(Structural formula)
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Polarity

• Molecule has a positive side and a negative side
• Due to unequal sharing of electrons
• Weak bonds form
• Called Hydrogen bonds

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Polarity

• These weak hydrogen bonds are important
• Causes water to attract other molecules
• Water can hydrogen bond with up to 4 other
  molecules

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Ionization

• Any process by which electrically neutral atoms
  or molecules are converted to electrically
  charged atoms or molecules (ions).
• Causes molecules to separate into simpler
  molecules, atoms, or ions
• Water attracts other ions and dissociates them
• Conduction of nerve impulses
• Contraction of muscles
• Digestion of food

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Ionization of Water
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Water has special properties due to hydrogen
bonding

• Cohesion attraction between water molecules
• Surface tension
• Flow of water
• Adhesion attraction between water and
  othermolecules
• Water sticking to windshield
• Capillary action movement of water against
  the pull of gravity
• Within plant stems

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Mixture

• 2 or more elements or compounds mixed together
• NOT chemically combined
• E.g.
• Soil
• Air
• Salt water

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Two types of mixtures

• 1. Solution 1 or more dissolved chemicals
• Solvent chemical that others dissolve in
• Solute chemical that is dissolved
• Water is the best solvent!!!
• Aqueous solutions solutions of water

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2. Suspensions

• Substances mixed in water, but not dissolved
• Molecules are suspended in the water
• E.g.
• Blood contains proteinsand cells
• Cytoplasm contains organelle

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pH Percent Hydrogen

• Indicates the concentration of H ions in
  solution
• Range 0 14
• pH 7 neutral concentrationof H and OH- is
  equal
• Each pH is 10X the concentration of the previous

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pH Percent Hydrogen

• Example
• Change in pH from 10 to 12
• concentration change equals
• 10 X 10 or
• 100

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Acids vs. Bases

• ACIDS BASES
• pH lt 7 pH gt 7
• Sour taste taste bitter
• Lots of H lots of OH-

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pH Scale
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Buffers

• Chemicals that neutralize small amounts of acids
  or bases
• Controls pH which is important to maintaining
  homeostasis
• Minimizes shifts in pH
• Normal pH in humans is 6.5 7.5

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Sodium hydroxide
Lye
Milk of Magnesia
Tums
Baking soda
Intestinal fluid
Urine
Spinach
Asprin
Cola
Battery acid
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Importance of Water to Living Organisms
abundant

• most __________ compound in living matter
• universal ________ - dissolves many things
• needed for __________ (metabolic) reactions
• ___________ materials
• __________ temperature
• needed to eliminate ________
• ________ and _________ vital organs
• __________ joints and tissues
• reservoir of ___ and ____ ions

solvent
biological
transports
regulates
wastes
protects
cushions
lubricates
OH-
H