Water is a transparent, odorless, tasteless liquid
composed of the elements hydrogen and oxygen. It is a very
good solvent, meaning that many substances can dissolve in
it easily. Water is important to our lives, and
without it we could not live. In fact, there are no
living creatures that can live without water.
It illustrates the three states
of matter: solid (ice), gas (steam), and liquid
(water).
The forms water
take, depends upon the temperature. At low temperatures,
the
molecules do not move around as much and form a
crystalline structure that is rigid (ice). In the
liquid state, water molecules move more freely. Water
molecules in the form of steam
are moving very fast with large spaces between the
molecules.
Although ice is crystalline, it tends to have the
molecules in a rigid structure that is spaced farther
than the molecules of liquid water and this is quite
important, for if ice were denser,
it would sink in water. Imagine what would happen if
icebergs
grew from the bottom of the ocean instead of floating on
the surface.
Water and hydrogen
peroxide are made of the same elements: oxygen and hydrogen. However,
hydrogen peroxide (H2O2) has 1 more oxygen than water (H2O).
Water is very
important to our everyday lives because of the manner in
which
hydrogen and oxygen "hold" hands. The water molecule is
very strong, but the way it is arranged,
allows many other substances that can "hide" between the
hydrogen
and oxygen. What makes water so important? Water is a
peculiar substance with properties that
make it an ideal fluid. If you theoretically calculate
the boiling and freezing
temperatures of water you will find that water has an
unusually low freezing point and
high boiling point compared to other molecules that have
similar
structures (sulfur, selenium, and tellurium).
How can you
explain such a big difference? The molecular structure of
water
resembles that of Mickey Mouse's head (figure right). The
hydrogen and the oxygen have a very tight
covalent bond, where the hydrogen and the oxygen share electrons as they
dance and twirl around in the molecule. The individual
molecules
of water are also held together very tightly by what is
specifically called a hydrogen bond. A
hydrogen bond is much stronger than other bonds that
molecules
have. Ionic bond is one of those weaker bonds, and
substances like salt can be easily be broken
up. Water is a package of power that is hard to break,
and it is
this strength that allows other substances to dissolve or
break up in water, hence the name,
universal solvent.
