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| Water is one of the most important molecules in chemistry, particularly biochemistry since water is essential for life. .
Water - The Key Component For Life
Properties of Water
Interesting Facts and Properties of Water
by Anne Marie Helmenstine, Ph.D.
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Water is the
most abundant molecule on the Earth's surface and one of the most important
molecules to study in chemistry.
Here's a
look at some facts about water chemistry.
What
Is Water?
Water is a chemical
compound. Each molecule of water, H2O or HOH, consists of two atoms
of hydrogen bonded to one atom of oxygen.
Properties
of Water
There are several
important properties of water that distinguish it from other molecules and make
it the key compound for life:
1. Cohesion a
key property of water. Because of the polarity of the molecules, water
molecules are attracted to each other. Hydrogen bonds form between
neighboring molecules.
Because of its cohesiveness, water remains
a liquid at normal temperatures rather than vaporizing into a gas. Cohesiveness
also leads to high surface tension.
An example of the surface tension is seen
by beading of water on surfaces and by the ability of insects to walk on liquid
water without sinking.
2. Adhesion
is another property of water. Adhesiveness is a measure of water's ability to
attract other types of molecules.
Water is adhesive to molecules capable of
forming hydrogen bonds with it.
Adhesion and cohesion lead to capillary
action, which is seen when the water rises up a narrow glass tube or within the
stems of plants.
3. The
high specific heat and high heat of vaporization mean a lot of energy is needed
to break hydrogen bonds between water molecules.
Because of this, water resists extreme
temperature changes. This is important for weather and also species survival.
The high heat of vaporization means
evaporating water has a significant cooling effect. Many animals use
perspiration to keep cool, using this effect.
4. Water
may be called the universal solvent because it is able to dissolve many
different substances.
5. Water
is a polar molecule. Each molecule is bent, with the negative charged oxygen on
one side and the pair of positive-charged hydrogen molecules on the other side
of the molecule.
6. Water
is the only common compound that exists in solid, liquid, and gas phase under
ordinary, natural conditions.
7. Water
is amphoteric, which means it can act as both an acid and a base.
Self-ionization of water produces H+ and OH- ions.
8. Ice
is less dense than liquid water. For most materials, the solid phase is denser
than the liquid phase.
Hydrogen bonds
between water molecules are responsible for the lower density of ice. An
important consequence is that lakes and rivers freeze from the top down, with
ice floating on water.
Water
Facts
· Other
names for water are: dihydrogen monoxide, oxidane, hydroxylic acid, and
hydrogen hydroxide
· the
molecular formula of water: H2O
· molar
mass of water: 18.01528(33) g/mol
· density
1000 kg/m3, liquid (4 °C) or 917 kg/m3, solid. This is
why ice floats on water.
· melting
point: 0 °C, 32 °F (273.15 K)
· boiling
point: 100 °C, 212 °F (373.15 K)
· acidity
(pKa): 15.74
· basicity
(pKb): 15.74
· refractive
index: (nD) 1.3330
· viscosity:
0.001 Pa s at 20 °C
· crystal
structure: hexagonal
· molecular
shape: bent
· Pure
liquid water at room temperature is odorless, tasteless and nearly colorless.
Water has a faint blue color, which becomes more apparent in large volumes of
water.
· Water
has the second highest specific enthalpy of fusion of all substance (after
ammonia). The specific enthalpy of fusion of water is 333.55 kJ·kg−1 at 0 °C.
· Water
has the second highest specific heat capacity of all known substances. (Ammonia
has the highest specific heat.)
Water also has a high
heat of vaporization (40.65 kJ·mol−1). The high specific heat and heat of
vaporization result from the high degree of hydrogen bonding between water
molecules.
One consequence of
this is that water is not subject to rapid temperature fluctuations. On Earth,
this helps to prevent dramatic climate changes.
Anne Helmenstine, Ph.D., is an author and
consultant with a broad scientific and medical background.
Experience
Anne has taught chemistry, biology, and physics
at the high school, college, and graduate level. In her doctoral work, Anne
developed ultra-sensitive chemical detection and medical diagnostic tests. She
has worked abstracting/indexing diverse scientific literature for the
Department of Energy. She presently works as a freelance writer and scientific
consultant. She enjoys adapting lab-based science projects so that they can be
performed safely at home.
Education
Dr. Helmenstine has bachelor of arts degrees in
physics and mathematics with a minor in chemistry from Hastings College in
Nebraska and a doctorate of philosophy in biomedical sciences from the
University of Tennessee at Knoxville.
Anne Marie Helmenstine, Ph.D.
Chemistry is part of everyone's life, from
cooking and cleaning to the latest computer chip technology and vaccine
development. It doesn't have to be intimidating and it doesn't have to be hard
to understand.
You can read more about Anne's current and past
work on her Google Profile: Anne Helmenstine. Find
Anne's printable periodic tables and science projects at Science Notes.
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