Answer:
High heat
capacity
*A large amount of heat energy
is required to raise the temperature of water.
*means that a large
increase in heat energy results in a relatively small rise in temperature
*because of the extensive
hydrogen bonds between its molecules
*heat energy must first
be used to break the hydrogen bonds.
*to stabilize the
temperature of water
*minimum changes in water
temperature provide a constant external environment for many cells and aquatic
organisms
*A constant body
temperature enables enzymes to function optimally and prevents denaturation of
biological molecules.
-High surface tension and cohesion
*Cohesion-phenomenon
where polar water molecules readily form hydrogen bonds with other water
molecules and the molecules tend to stick together.
*the hydrogen bonding
between water molecules results in strong cohesive forces
*Adhesive force is the
attractive force between two different types of molecules.
*Surface tension-exists
between the molecules at the surface of a liquid as a result of inwardly acting
cohesive forces between the molecules
*Water has a greater surface
tension than most other liiquids
*the molecule on the surface has a minimal surface area,
causing high surface tension
*important
in translocation of water through xylem plants
*creates an unbreakable
flow of water in xylem
*As water evaporates from
leaves, the unbroken columns of water held by cohesive forces within the narrow
xylem vessels are drawn upwards to the top of trees .Adhesion of water to the
xylem wall resists the downwards pull of gravity.
*At air-water interface;
for example, at the surface of ponds, the inwardly cohesive forces produce high
surface tension at the surface of water.
*This allows small
organisms like the pond skater, to move over its surface.
-Solvent
properties
*Water is an excellent
solvent for polar substances.(able to dissolve polar substances)
*due to the polar nature
of water molecules and hydrogen bonds between water molecules
*non polar substance that
do not dissolve in water=hydrophobic
*include ionic substances
like salts, whose charged particles (ions)dissociate in water when the
substance dissolves, and some non-ionic substances like sugars and simple
alcohols which contain charged(polar)groups within the molecules, such as the
hydroxyl (-OH)groups of sugars and alcohols
*medium for chemical
reactions to take place
*as a transport medium
*as in the blood, lymphatic
and excretory systems, the alimentary canal and in xylem and phloem of plants
-Density and
freezing properties
*As water cools, the
movement of water molecules slow down and the molecules are further apart.
*Each water molecules can
form a maximum number of four hydrogen bonds with the other water molecules.
*the volume of water
decreases and density increases as it cools to 4 °C
*as water cools below 4°C, its volume increases and density
decreases
*Thus, water solidifies
with an increase of volume
*At below 4°C, ice becomes less dense than liquid
water and floats at the surface forming an insulating layer. This prevents
water from freezing in lower depth and slowing down its temperature drop.
*water expands as it
freezes, therefore its solid form is less dense than liquid form.
*the lattice crystal
occupies a bigger space and has fewer molecules compared to an equal volume of
liquid and floats in the liquid water
*ensures the survival of
aquatic organisms during winter.
*At below 4°C, water rises to the surface. This
movement leads to water circulation.
-low viscosity
*because hydrogen bonds between water
molecules are being continually broken and reformed
*can slide
easily over each other and are able to flow with less friction through narrow
vessels.
*Blood vessels
and watery solutions can act as lubricants to allow food to move easily down
the alimentary canal.
*aquatic organisms can move easily in
water
Assignment submitted by S.M., Kang, E.S., Ong, T.W., Tan 2011/2012 (IBM)
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