Answer:
Physical Properties
Water is primarily a liquid under standard conditions,
which is not predicted from its relationship to other analogous hydrides of the
oxygen family in the periodic table, which are gases such as hydrogen sulfide.
The elements surrounding oxygen in the periodic table, nitrogen, fluorine,
phosphorus, sulfur and chlorine, all combine with hydrogen to produce gases
under standard conditions. The reason that a water form a liquid is that oxygen
is more electronegative than all of these elements with the exception of
fluorine. Oxygen attracts electrons much more strongly than hydrogen, resulting
in a net positive charge on the hydrogen atoms, and a net negative charge on
the oxygen atom.
Water has a high specific heat capacity. This means that
water can absorb a lot of heat before it begins to get hot. The specific heat
of water is 4.2 J g-1 °C-1 .This is much higher than that
of most other liquids because of its extensive hydrogen bonding. Heat energy must
first be used to break the hydrogen bonds. This means that water does not
change temperature easily.
Besides that, 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. This allows small organisms like the
pond skater, to move over its surface. Water molecules, being polar, readily
form hydrogen bonds with other water molecules. The molecules tend to stick
together and cause cohesion.
Chemical Properties:
Water is the chemical substance with chemical formula H2O: one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom. Water is a tasteless, odorless liquid at ambient temperature and pressure, and appears colorless in small quantities, although it has its own intrinsic very light blue hue. Ice also appears colorless, and water vapor (steam) is essentially invisible as a gas.
Oxygen attracts electrons much more strongly than
hydrogen, resulting in a net positive charge on the hydrogen atoms, and a net
negative charge on the oxygen atom. The presence of a charge on each of these
atoms gives each water molecule a net dipole moment. Electrical attraction
between water molecules due to this dipole pulls individual molecules closer
together, making it more difficult to separate the molecules and therefore
raising the boiling point. This attraction is known as hydrogen bonding.
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.
Importance
of the properties of water to the living organisms
Surface tension of water 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.
Properties of water allow water to moderate Earth's
climate by buffering large fluctuations in temperature. According
to Josh Willis, of NASA's Jet Propulsion Laboratory, the oceans absorb one
thousand times more heat than the atmosphere (air) and are holding 80 to 90% of
global warming heat.
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Functions
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Examples
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1.
Cell Structure
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Important
component of protoplasm (60-95%)
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2.
Solvents and hydrolysis
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Solvent for solutes, provides an aqueous medium for
biochemical reactions
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Hydrolyses polysaccharides into monosaccharide,
proteins into amino acids, fats into fatty acids and glycerol.
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3.
Metabolites
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Water
is required for photosynthesis.
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4.
Medium for diffusion
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Enables
diffusion of substances across membranes such as in the alveolus.
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5.
Transport medium
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Blood plasma transports food, gases, hormones, salts, antibodies
and wastes.
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Helps in osmoregulation of body fluids.
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6.
Support
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Hydroskeleton in earthworm. Turgid cells give support
to herbaceous plants.
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Aqueous and vitreous humours give shape and support to
the eyeball
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Amniotic fluid supports and protects the foetus in the
amniotic sac.
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7.
Lubricants and secretions
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Mucus in alimentary canal.
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Synovial fluid in joints.
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Needed to form digestive juice, lachrymal fluid
(tears), sweat and nectar.
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8.
Habitat
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Provides
an aquatic environment and support to aquatic organisms like whales and other
fishes.
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9.
Medium for movement, dispersal and migration
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Medium for swimming gametes, larval stages, dispersal
of fruits and seeds.
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Water is needed to break the pericarp of some fruits
and their testa for germination.
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10.
Temperature control
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Evaporation
of sweat cools the body
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11.
Transpiration
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Creates
tension to pull water and dissolved salts from the roots to the aerial parts.
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Assignment submitted by Miller Ng, 2011/2012(IBM)
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