Structure and Properties
Water
Water around us
Water is everywhere.
Most abundant molecule in living things.
2 WATER COVERS MORE THAN THE
¾ OF EARTH’S SURFACE ARE
COVERING BY WATER
Water around us
3 WATER CONSTITUTES MORE THAN THE 70% OF HUMAN BODY
72%
Chemistry of Water
Water has unique life- supporting properties like:
• Lower density in solid state than in liquid phase
• Cohesion
• Adhesion
• Capillary action
How does its structure contribute to these properties?
Watch this to answer this question.
Chemistry of Water
Properties of Water
Hydrogen Bonds
• Polarity causes water
molecules to attract each other
like magnets
• H (+) attracts O (-) forming a
hydrogen bond
• Gives water special properties
Properties of Water
Lower density of ice than liquid water
Since ice is less dense than
the water, bodies of water
freeze from the top to the
bottom.
Provides insulation to the
water under the ice,
preventing all the water from
freezing.
This allows life to continue
under the ice, provided there
is sufficient nutrients.
There are fewer
molecules in the
same space of
ice than in liquid
water.
Properties of Water
Cohesion and Surface Tension
The cohesive forces between molecules down into a liquid
are shared with all neighboring molecules.
Molecules on the surface have no neighboring molecules
above, and so exhibit stronger intermolecular attractive
forces upon their nearest neighbors on the surface called
surface tension.
Properties of Water
Cohesion and Surface Tension
Because of the natural cohesive forces
between water molecules and the fact that
surface molecules have a surface tension,
without a container, water forms spheres
Little insects can freely run along the
surface of a pond.
They are supported by the high
surface tension.
Properties of Water
Adhesion
• Adhesion- attraction between the water the
straw surface – resulting in a curved surface
(meniscus)
Meniscus
Properties of Water
Capillary Action
Capillarity action- Adhesion
between water molecules
and the walls of the tubes
helps resist the downward
pull of gravity on the water.
Properties of Water
Temperature Moderation
Because of hydrogen bonding, water has a better ability
to resist temperature changes than most other
substances.
It allows the body’s temperature control, avoid drastic
changes of temperature that affect aquatic species, and
explains the differences of temperatures between
coastal and continental places.
• Effect of large specific heat capacity of water