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Slide 1

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Why do we need water ?
Most abundant solvent
Cytoplasm of cells ­ reactions to occur
Chemical reactions ­ hydrolysis & photosynthesis
Acts as a coolant in plant & animals
Provides habitats
Blood ­ transport fluid…read more

Slide 2

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Describe how hydrogen bonding occurs between water
Water consists of 2 hydrogen atoms covalently bonded to one
oxygen atom.
Shared electrons are not evenly shared.
Oxygen is slightly negatively charged and the hydrogen is slightly
positively charged.
Opposite charges attract so water molecules are attracted to one
Water is described as being polar (hydrophilic).…read more

Slide 3

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Relate this and other properties of water, to the role of water in living
Solvent Liquid Cohesion
Metabolic processes in all The movement of Water molecules stick
organisms rely on chemicals materials around to each other creating
being able to react together organisms, both in cells surface tension at the
in solution and on a large scale in water surface.
70 ­ 95 % of cytoplasm in multicellular organisms, Cohesion also makes
water. Dissolved chemicals requires a liquid transport long, thin water
take part in processes such medium. Blood in animals columns very strong
as respiration and and the vascular tissues in and difficult to break.
photosynthesis in living plants use water as a Transport of water in
organisms. liquid transport medium. the xylem relies on
water molecules
sticking to each other
as they are pulled up
the xylem in the
transpiration stream.
Some small
organisms make use
of surface tension to
walk on water.…read more

Slide 4

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Freezing Thermal Metabolic
Water freezes, Stability Water takes part as a
forming ice on the Large bodies of reactant in some
surface. Water water have fairly chemical processes.
beneath the surface constant Water molecules are
becomes insulated temperatures. used in hydrolysis
and less likely to Evaporation of reactions and in the
freeze. Organisms water can cool process of
such as polar bears surfaces by photosynthesis.
live in an removing heat.
environment of Oceans provide a
floating ice packs. relatively stable
Lakes tend not to environment in
freeze completely, terms of
so adequate temperature. Many
organisms aren't land based
killed as organisms use
temperature fall. evaporation as a
cooling mechanism,
for example in
panting or sweating.…read more


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