Activity Books Watershed Defenders Comic Book | Page 10

H 2 O—T he A mazing M olecule
We can’t live without water. We know
that, but have you ever thought about
how unique the stuff is?
How many other substances can
you think of that you can find in the
natural environment in a solid, liquid
and vapor form?
It’s a trick question. There aren’t any.
Water never goes away. Earlier we
saw the water cycle in action, but it
goes beyond that. Water is difficult
to destroy no matter how hard you
try. You can boil it, freeze it or try to
smash it, but it’s still water.
Water is a simple molecule—two
hydrogen atoms connected to an oxy-
gen atom. You’ve undoubtedly seen the
formula written as H 2 O. The magnetic
attraction of these particles is so strong
that the bonds are tough to break.
You might think that those two hy-
drogen atoms would be on opposite
sides of the oxygen, but they’re not.
They always sit precisely at a 104.5
degree angle, as in the picture. The
molecule sort of looks like the ears on
that famous mouse character.
The angle of the atoms is impor-
tant. It gives water special properties.
One side of the molecule has a posi-
tive electric charge, while the other is
negative. This polar charge attracts
the molecules to each other.
In addition, the polar charge dic-
tates which substances will readily
dissolve in water. When you make
lemonade, you put sugar and lemon
juice in water. The sugar and juice mix
easily, dissolving in the water.
The fact that water dissolves things
like sugar and salt, is one key to how
your body works. Water transports nu-
trients and wastes around the inside of
your body. When you sweat, the evap-
oration of the water cools your skin.
However, If we try
to mix oil and wa-
ter, the oil won’t
dissolve in the
water. It will
rise to the
ydrogen
top. Oil mol-
ecules
are
non-polar.
Here’s an-
other example:
If you get oil on
your hands, what
happens if you
wash with just
water? Not much
happens because
the water won’t
dissolve the oil.
If you get mud
on your hands, it
washes off with just
water.
Polarity not only helps
water dissolve lots of sub-
stances, but creates a most unusual
phenomena when we freeze it.
Most liquids shrink as they be-
come solids. Water expands, leaving
room for air spaces when it freezes.
This is why ice floats.
Think about that for a minute. If
ice didn’t float, we wouldn’t be here.
Lakes, springs and oceans would
freeze solid, instead of having the ice
on top. No liquid water, no life.
Sometimes, however, water’s abil-
ity to dissolve things is a problem.
Let’s say we spread fertilizer on a
football field to help the grass grow,
but we spill some on the driveway.
When it rains or the snow melts,
the water dissolves the fertilizer and
carries it to the storm drain—you
guessed it-we’re contributing to runoff
ydrogen
xygen
pollution.
Here’s
some-
thing else
to think
about. If
we take a
wheat seed and
place it in a cup of
dirt, nothing hap-
pens. That seed will
sit in there for years,
but if we add water,
a plant grows. It hap-
pens every day. There’s
nothing else like it. Now that’s an
amazing molecule.
During a 100-year period,
a water molecule spends approximately 98 years in the ocean,
20 months as ice, t wo weeks in lakes
and less than one week in the atmosphere.
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Watershed Defenders produced by Colorado Foundation for Agriculture