The Extraordinary
Properties of Water
Water
• A water molecule (H2O), is
made up of three atoms: one
oxygen and two hydrogen.
H
H
O
The Water Molecule
• Polarity
– A water molecule is polar because
there is an uneven distribution of
electrons between the oxygen and
hydrogen atoms.
(-)
(+)
•Polar water molecules
act like magnets
and attract each other
Hydrogen Bonds
-form between the negative end of
one water molecule and the positive
end of another.
-a hydrogen bond is weaker than an
ionic or covalent bond
BP and FP of Water
•At sea level, pure water boils at
100 °C and freezes at 0°C.
•212°F and 32°F
Properties of Water
• Cohesion
Properties of Water
• Cohesion
• Adhesion
Properties of Water
• Cohesion
• Adhesion
• High Specific Heat
Properties of Water
• Cohesion
• Adhesion
• High Specific Heat
• High Heat of Vaporization
1. Cohesion
•Attraction between particles of
the same substance
- Explains why water is
attracted to itself
Results in:
Surface tension (a
measure of the
strength of water’s
surface)
allows insects to
walk on the
surface of water
Jesus Lizard
• The Basilisk lizard makes use of the high surface
tension of water to accomplish the incredible feat
of walking on water's surface. The Basilisk can't
actually walk on water; rather, it runs on water,
moving its feet before they break through the
surface. Take a look:
• The 'Jesus' Lizard (473k movie)
• http://www.visionlearning.com/library/module_vie
wer.php?mid=57
2. Adhesion
•Attraction between two different
substances.
- water forms hydrogen bonds with
other surfaces such as glass, soil, plant
tissues, and cotton.
.
• Explains capillary actionwater molecules will pull
each other along when in a
thin glass tube.
• i.e. moves water up the
tubes of plants from roots
to leaves
3. High Specific Heat
Amount of heat needed to raise or
lower 1g of a substance 1° C.
•Water can absorb or release a lot
of heat energy with little change in
temperature.
As a result, water warms slowly and
cools slowly.
So, the oceans store heat.
And, the body (mostly water) does not
lose heat easily.
4. High Heat of
Vaporization
For water to evaporate, hydrogen
bonds must be broken. As water
evaporates, it removes a lot of
heat with it.
The “extra” energy needed to break
hydrogen bonds means that
evaporating water cools surfaces.
Explains why sweating is a great way
to stay cool.
5. Water is Less Dense as
a Solid
•Ice is less dense than liquid water
(ice floats).
•In winter, ice floats on lakes.
Explains why
fish can live
in a lake in
the winter;
the lake
freezes from
the top down.
Water as a Solvent
• The partial charges on water
molecules help make it an
excellent solvent.
• Water dissolves many
substances by surrounding
charged particles and "pulling"
them into solution.
For example, common table
salt, sodium chloride, is an
ionic substance that contains
alternating sodium and
chlorine ions.
When table salt is added to
water, the partial charges on
the water molecule are
attracted to the Na+ and Clions. The water molecules
surround the ions, separate
them, and slowly dissolve the
salt.
Negative oxygen ends of water
molecules will surround the
positive sodium ions.
Positive hydrogen ends will
surround the negative
chlorine ions.