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Ice = less than 0°C
(solid)
Water = 0°C – 100 ° C
(liquid)
Steam = greater than
100 °C
(gas)
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
Water consists of an
oxygen atom bound to
two hydrogen atoms by
two single covalent
bonds.
 Oxygen has unpaired
& paired electrons
which gives it a
slightly negative
charge while
Hydrogen has no
unpaired electrons
and shares all others
with Oxygen
 This leaves the
molecule with
positively and
negatively charged
ends
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


Cohesion
Adhesion
Capillarity
High Specific Heat
High Heat of Vaporization
Solid water (ice) is less dense than liquid
Solvent
Transparent
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

Water clings to polar
molecules through
hydrogen bonding
Cohesion refers to
attraction to other
water molecules,
and is responsible
for surface tension
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
Adhesion refers
to attraction to
other
substances.
Water is
adhesive to any
substance with
which it can
form hydrogen
bonds.
Bluebonnet leaves
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water evaporates from
leaves = transpiration
adhesion,
cohesion
and
capillary
action
roots take up
water by
capillary action
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•trees have specialized structures to transport water:
xylem and phloem “plumbing”
• water molecules are “dragged” from the roots to the top
of the tree by capillary action and cohesion: hydrogen
bonds help water molecules stick to each other
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
Specific Heat
 Amount of heat required to change the
temperature of 1g of a substance by 1o C.
 Because of water’s high specific heat, it
is used as a coolant in many systems.
Car engine with radiator
Comanche Peak Nuclear
Power Plant Glen Rose, TX
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A large body of water can absorb a
large amount of heat from the sun in
daytime and during the summer,
while warming only a few degrees.
At night and during the winter, the
warm water will warm cooler air.
Therefore, ocean temperatures and
coastal land areas have more stable
temperatures than inland areas.
The water that dominates the
composition of biological organisms
moderates changes in temperature
better than if composed of a liquid
with a lower specific heat.
The Earth is over
75% water!
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Heat of Vaporization
 Amount of energy required to change 1g of liquid
water into a gas (586 calories).
 large number of hydrogen bonds broken when
heat energy is applied
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Evaporative cooling.



As a liquid evaporates, the surface of
the liquid that remains behind cools –
this is called evaporative cooling.
Evaporative cooling moderates
temperature in lakes and ponds and
prevents terrestrial organisms from
overheating.
Evaporation of water from the leaves of
plants or the skin of animals removes
excess heat.
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
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

A liquid that is a completely homogeneous
mixture of two or more substances is called a
solution. This consists of the solute and solvent.
 A sugar cube (solute) in a glass of water (solvent)
will eventually dissolve to form a uniform
mixture of sugar and water (solution).
The dissolving agent is the solvent and the
substance that is dissolved is the solute.
 In our example, water is the solvent and sugar
the solute.
In an aqueous solution, water is the solvent.
Water is not really a universal solvent, but it is
very versatile because of the polarity of water
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molecules.

Water is an effective
solvent as it can form
hydrogen bonds.
 Water clings to
polar molecules
causing them to be
soluble in water.
 Hydrophilic attracted to water
 Water tends to
exclude nonpolar
molecules.
 Hydrophobic repelled by water
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Water transports molecules dissolved in it

Blood, a water-based
solution, transports
molecules of nutrients
and wastes organisms

Nutrients dissolved in
water get transported
through plants

Unicellular organisms
that live in water absorb
needed dissolved
substances
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
Ice is less dense than water: the molecules are
spread out to their maximum distance
Density = mass/volume
same mass
but a larger
volume
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 water expands as it
solidifies
 water reaches maximum
density at 4°C
 water freezes from the top
down
 organisms can still live in
the water underneath the ice
during winter
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
The fact that water
is clear allows light
to pass through it
Aquatic plants can
receive sunlight
Light can pass
through the eyeball
to receptor cells (in
the back of the eye)
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