Chapter 2
Chemical Foundations
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Hydrogen Bond
 Weak bond resulting from hydrogen’s
slight positive charge attracting to an
atom with a slight negative charge
Properties of Water
Water is Fundamental to
Life
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Special Properties of Water
 Polar Molecule
 Temperature Stabilizing Effect
 Cohesion and Adhesion
 Solvent Properties
Polar Molecule
 In the covalent bonds between Oxygen
and 2 Hydrogen, the electrons are not
shared equally
 The electrons spend more time around
the Oxygen which results in a more
negative charge, and less time around
the Hydrogen resulting in a more
positive charge
Due to the polarity of water, it is
attracted to other polar molecules
These are Hydrophilic
substances
Due to the polarity of water, it is
repelled by non-polar molecules
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These are Hydrophobic
substances
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Temperature Stabilizing Effect
 H-bonds between water molecules
absorb or lose energy without the
particles speeding up or slowing
down.(Absorb energy without change in
temp.)
 High heat capacity
 As a result water is slow to cool and
slow to heat
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Ice
Water
 As a result Ice Floats on water
 This is called the density anomaly.
Cohesion
 Due to H-bonds, water resists rupturing
(stretches) under pressure
Capillary Effect
Adhesion
 Attraction of water to other substances
and surfaces
 plants are able to get water up their
stems because of cohesion and
adhesion
Solvent Properties
Ions and polar molecules easily dissolve
in water.
Due to polarity, water molecules align
themselves around charged atoms and
molecules to form spheres of hydration
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Due to polarity, water molecules form
spheres of hydration around charged
atoms and molecules.
Blood, sap and all of life’s fluids are water
based.
Other Chemistry
Acid
 Substance that releases hydrogen ions
(H+, protons or hydronium ion) in
solution
 Accepts OH pH below 7
Base
 Substance that releases hydroxide ions
(OH-, hydroxide ion) in solution
 Accepts H+
 pH greater than 7
 Fluid inside most human
cells has a pH of 7
 Fluids surrounding cells
(interstitial fluid) and
blood have a pH
of 7.3 - 7.5
Maintaining proper pH is
essential to life systems
 Blood pH of 7 or below leads to a coma
 Blood pH 7.8 or higher leads to tetany
(uncontrolled muscle contractions)
Buffer System
 Partnership of weak acids and weak
bases that work to counter shifts in pH.
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Salts
 Compounds that release ions other than
OH- and H+ in solution.
 Na+, K+ and Ca++ are some that are
important in biology