40
Matter and Materials
WATER
The simple combination of two hydrogen atoms and one oxygen
atom creates a water molecule (H2O). Water is the most common
compound on Earth, making up over half the weight of living
things. It is vital to life, bringing nutrients to and taking away
waste from every living cell. Water molecules are attracted to one
another through HYDROGEN BONDS, and this gives water some
unusual but useful properties.
Oceans, rivers,
and lakes cover
three-quarters of
Earth’s surface
ABUNDANCE OF WATER >
Water covers around 70 percent of
Earth’s surface. This is why Earth
looks blue from space, and why
it is often called the “Blue
Planet.” Water is liquid in the
oceans and forms solid ice
caps at the ice caps. Water
vapor is a gas in air. Humid
places, such as rainforests,
have a lot of water vapor.
The human body is about
60 percent water; a ripe tomato
contains over 95 percent water.
Arctic ice cap is
approximately the
same size as the
United States
Gaseous water
is found as vapor
everywhere
water
DRINKING WATER >
At room temperature, pure water is
a colorless liquid with a neutral pH—
it is not an acid or a base. But most
water is not pure. Hard water contains
calcium and magnesium minerals,
which have dissolved in the water as it
flows over rocks. Soap does not lather
well in hard water—the minerals react
with the soap to form a scum. Hard
water is softened by boiling or by
passing it through a water softener.
Dissolved potassium permanganate
crystals turn the water purple
< UNIVERSAL SOLVENT
The chemical potassium permanganate
dissolves in water to form a pink liquid. More
substances dissolve in water than in any
other liquid. Its molecules are small and have
a slight electrical charge, so they can move
around and interact with other particles. If
water did not have this property, life could
not exist. Water is nature’s carrier. Dissolved
gases, such as oxygen and carbon dioxide, are
carried by water to and from all living cells.