Water
The Magic Molecule…..
Properties of Water
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Water is one of the
most unique
substances found in
the universe and all
of life depends on it.
A simple molecule
formed by the
sharing of electrons
(covalent bond)
between one
oxygen and two
hydrogen
Water is a polar molecule...
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Oxygen attracts the shared e- in H2O
much more strongly than does H, so
the shared e- are closer to the O atom
than to the H atoms.
This makes the H slightly positive and
the O slightly negative. (Technically still
neutral, p+=e-)
Thus, the H in water is attracted to the
O of other water molecules and vice
versa.
This type of bond is called a hydrogen
bond, one of the weakest bond types,
but very important!
Physical Properties:
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Water is called the "universal solvent"
because it dissolves more substances
than any other liquid. This means that
wherever water goes, either through the
ground or through our bodies, it takes
along valuable chemicals, minerals, and
nutrients.
Water is neutral on the pH scale.
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Pure water has a
neutral pH of 7,
which is neither
acidic nor basic.

Rain has a
naturally acidic pH
of about 5.6
because it contains
natural derived
carbon dioxide and
sulfur dioxide.
All 3 states are common!
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Water is unique in
that it is the only
natural substance
that is found in all
three states -- liquid,
solid (ice), and gas
(steam) -- at the
temperatures
normally found on
Earth.
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Water is unusual in that
the solid form, ice, is
less dense than the
liquid form, which is why
ice floats.
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When water is frozen its
molecules arrange
themselves in a
particular highly
organized rigid
geometric pattern that
causes the mass of
water to expand and to
decrease in density.
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Water freezes from the
outside to the inside.
This creates a barrier
between the harsh
environment and the
water underneath.
How would this be
good for life in rivers,
ponds and streams?
What would happen if
it froze from the inside
out?
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Water has a high specific heat.
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Specific heat is the amount of energy required
to change the temperature of a substance.
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Because water has a high specific heat, it can
absorb large amounts of heat energy before it
begins to get hot.
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It also means that water releases heat energy
slowly when situations cause it to cool.
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Water's high specific heat allows for the
moderation of the Earth's climate and helps
organisms regulate their body temperature
more effectively.
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Water has a high specific heat index.
This means that water can absorb a lot
of heat before it begins to get hot.

Why is water is valuable to industries
and in your car's radiator as a coolant.
A Question...

Explain why the
temperature
change between
seasons is
gradual rather
than sudden,
especially near
the oceans
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Hydrogen bonds only last a few
trillionths of a second, yet at any
instance most of the water molecules
are bonded to other.

The tendency to stick together is called
cohesion.
Surface tension

Surface tension is a measure of the strength
of the water's surface film. The attraction
between the water molecules creates a
strong film, which among other common
liquids is only surpassed by that of mercury.
More on surface tension...
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Surface tension is essential for the transfer of
energy from wind to water to create waves.
Waves are necessary for rapid oxygen
diffusion in lakes and seas.
Capillary Action
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Also called capillarity
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What are some other examples of
where this occurs?
Capillary Action
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Surface tension is
responsible for
capillary action.
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May be defined as the
ability of a liquid to
climb up a surface
against the pull of
gravity
Capillary Action
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For example, in a thin glass tube, when the
molecules at the edge adhere to the molecules of
glass just above them, they (at the same) time pull
other water molecules along with them.
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The water pulls the entire body of water
to a new level causing
the liquid to rise
because the water is in
contact with the solid.
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Thus water readily
wets many
materials. (Capillary
action allows a
paper towel or a
sponge to be used
to soak up spilled
water.) Without this
property, the
nutrients needed by
plants and trees
would remain in the
soil.
Water Cycle
OK then,
Water..The Magic Molecule

What are the properties that make it so
unique?
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Can you DESCRIBE 6?
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Could you explain them in paragraph
form?