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Molecular Structure of Water
Water has a variety of unique properties, many of
which are a result of its unusual shape. Water molecules consist of two
hydrogen atoms and one oxygen atom. Hydrogen and oxygen are both gases,
but they combine to form a liquid compound: water,
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The two hydrogen atoms form an angle of about 105 degrees
with the oxygen atom. This angle produces an asymmetrical molecule with
the oxygen atom dominating one end of the molecule and hydrogen atoms dominating
the other end. This asymmetry causes the oxygen end to have a slight negative
charge and the hydrogen end to have a slight positive charge.
A molecule that has (+) and (-) poles like this is called
a polar molecule and can act like a magnet. The (+) end of the one water
molecule repels the (+) of another and attracts another molecule's (-)
end. This arrangment holds water molecules together at normal temperatures
and makes it a liquid.
Physical States of Water
Water can exist as a solid, liquid or vapor, depending on its temperature.
Water molecules can be moving so fast that they are not connected to each
other (vapor); or can be slowed so they are touching other water molecules
(liquid); or the molecules can be locked together in crystal form (solid
/ ice). As the temperature of liquid water is raised above the boiling
point or decreased below its freezing point, its state changes.
Carbon dioxide may be the most important material that
dissolves in water because it determines the acidity of the water. It
causes water to be a weak acid, which increases the water's ability to
dissolve materials. That is partially responsible for physical and chemical
changes on Earth (erosion, soil deposition, leaching, etc.).
Water, like most substances, has its own specific properties.
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