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Water: Structure and Properties
Introduction
Water is a main component of all the living
beings
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Some properties of the water
cannot be explained clearly by the
experiments
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He wrote
the book “
The fitness of the environment:
An inquiry into the biological significance of
the properties of matter”

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03 nm3 at room temperature and
pressure
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The surface tension,
viscosity and specific heat capacity are also
high due to the H- bondings
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Water has a high dielectric constant
and different expansion properties when
compared with other liquids
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High specific heat of ice and high heat of
vaporization of vapour help in cellular and
physiological levels to the living organisms
for heat transfer, temperature regulation,
cooling etc
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The high surface tension makes a
barrier and helps to walk on the water
surface to the small insects like organisms
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The
expansion of water upon cooling below 4 0C
and upon freezing help to maintenance of
the protection of the organisms in polar
regions by making ice caps on the top of the
oceans and lakes
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It
has two O-Hbonds and the bond length is0
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The angle between the two bonds
is 104
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Water molecule
has a sphere shape
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Dielectric constant
The dielectricconstant of water is 80 times t
he dielectric constant of vaccum and the
polarization ability is higher than most of
organic molecules
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The permanent dipole moment of
the molecules
2
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How easily they can reorient in
response to a field
4
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When consider the water it has a high
dipole moment and due to its small size the
density of dipole also high
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The
polarizability and flexibility of water give a
small support for the dielectric constant
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When the temperature is increased
the dielectric constant isincreased
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Therefore the O-H
bond is highly polarized
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The spontaneous ionization of water can be
expressed by the dissociation constant of
water
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82×10 -16 m ol l-1

a base or accept H+ from an acid
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Signal and energy transmission
inside the biological systems can be done
rapidly due to these reactions
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The liquid phase is important for living
things
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In the water vapour
the H-bond strength is 22
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But in
solid state and liquid state the H-bond
depends on geometry and the surrounding
molecules
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In ice-I the water
molecules are arranged in a tetrahedral
lattice
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2 H atoms in
water make H-bonds with another 2 O
atoms and O atom makes two H-bonds with
another two water molecules
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Effect of solutes
As 25oC the H+ concentration in pure water
is 1
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The mobility of
the H+ ions in water is done by a hopping
mechanism
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The self ionization ability of water
helps it to exchange the OH- and H+ with
many of polar solutes
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Angular structure of water also
affect on solutes
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But they make
vander waals interactions
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These
groups tend to remove the weakly Hbonded facial water in the coordination
shell thus reduce the population of more
bent H-bonds
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Hydrophobic and hydrophilic
interactions
Water asa solvent
Water is very important for living beings as
a solvent
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Water is a
universal solvent
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Hydrocarbons, aromatic
amino acids dissolve in water in fewer
amounts
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Some
other molecules cannot be differentiated
ass hydrophobic and hydrophilic
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If it is positive, the water solubility is
low
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Hydration of a solute occursin two steps:
1
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Place the solute in that cavity
The solubility is determined by two major
factors: They are cavity contribution and
the electrostatic contribution

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