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Before we begin looking at the properties of water, maybe
you'd like to take our True/False quiz
about water properties. Some of the answers may surprise you.
What are the physical and chemical properties of water that make it so
unique and necessary for living things? When you look at water, taste and
smell it - well, what could be more boring? Pure water is virtually colorless
and has no taste or smell. But the hidden qualities of water make it a most
interesting subject.
Water's Chemical Properties
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You probably know water's chemical description is H2O.
As the diagram to the left shows, that is one atom of oxygen bound to two
atoms of hydrogen. The hydrogen atoms are "attached" to one side
of the oxygen atom, resulting in a water molecule having a positive charge
on the side where the hydrogen atoms are and a negative charge on the other
side, where the oxygen atom is. Since opposite electrical charges attract,
water molecules tend to attract each other, making water kind of
"sticky." As the right-side diagram shows, the side with the
hydrogen atoms (positive charge) attracts the oxygen side (negative charge)
of a different water molecule. (If the water molecule here looks familiar,
remember that everyone's favorite mouse is mostly water, too).
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All these water molecules attracting each other mean they tend to clump
together. This is why water drops are, in fact, drops! If it wasn't for some
of Earth's forces, such as gravity, a drop of water would be ball shaped -- a
perfect sphere. Even if it doesn't form a perfect sphere on Earth, we should
be happy water is sticky.
 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.
Pure
water has a neutral pH of 7, which is neither acidic nor basic.
 Diagram
about pH
Water's Physical Properties
- 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. Earth's water is constantly interacting, changing, and in movement.
- Water freezes at 32o
Fahrenheit (F) and boils at 212o F (at sea level, but 186.4°
at 14,000 feet). In fact, water's freezing and boiling points are the
baseline with which temperature is measured: 0o on the
Celsius scale is water's freezing point, and 100o is water's
boiling point. Water is unusual in that the solid form, ice, is less dense
than the liquid form, which is why ice floats.
- Water has a high
specific heat index. This means that water can absorb a lot of heat
before it begins to get hot. This is why water is valuable to industries
and in your car's radiator as a coolant. The high specific heat index of
water also helps regulate the rate at which air changes temperature,
which is why the temperature change between seasons is gradual rather
than sudden, especially near the oceans.
- Water has a very high
surface tension. In other words, water is sticky and elastic, and tends
to clump together in drops rather than spread out in a thin film.
Surface tension is responsible for capillary action, which
allows water (and its dissolved substances) to move through the roots of
plants and through the tiny blood vessels in our bodies.
- Here's a quick rundown
of some of water's properties:
- Weight: 62.416
pounds per cubic foot at 32°F
- Weight: 61.998
pounds per cubic foot at 100°F
- Weight: 8.33
pounds/gallon, 0.036 pounds/cubic inch
- Density: 1 gram per
cubic centimeter (cc) at 39.2°F, 0.95865 gram per cc at 212°F
By the way:
1 gallon = 4 quarts = 8 pints = 128 ounces = 231 cubic inches
1 liter = 0.2642 gallons = 1.0568 quart = 61.02 cubic inches
1 million gallons = 3.069 acre-feet = 133,685.64 cubic feet
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Water properties
true/false quiz 
