in the presence of strong ultraviolet light from the sun,
leading to reactions with more oxygen molecules,
which produce ozone - O3.
oxygen
ozone 3O2(g) + ultraviolet light
2O3(g)gcsescience.com 8 gcsescience.com
Ozone Layer.
Oxygen decomposes
high up in the atmosphere
in the presence of strong ultraviolet light from the sun,
leading to reactions with more oxygen
molecules,
which produce ozone -
O3.
oxygen
ozone
3O2(g)
+ ultraviolet light 2O3(g)
Ozone
then acts to absorb (soak up) ultraviolet
light
and prevent it reaching the planet's
surface.
This is the so-called 'ozone
layer'.
It is essential for complex living
organisms (like you and me) to exist.
Without the ozone layer, all but very simple life
forms
would be destroyed by the action of ultraviolet
light.
Some chemicals, particularly CFCs, destroy
ozone in the upper atmosphere.
A CFC is a chlorofluorocarbon molecule.
It is similar to an alkane with all the
hydrogen atoms
replaced with
chlorine and fluorine atoms.
In the presence of ultraviolet
light a CFC molecule will
decompose
producing highly reactive chlorine
free radicals.
These chlorine free radicals will react with ozone
molecules
and turn them back into oxygen
molecules.
When this happens on a
large scale, a great deal of ozone
is lost
and a so called "hole" in the
ozone layer appears.
The hole allows more ultraviolet light to reach the surface of the Earth
which leads to a higher
risk of sunburn,
faster ageing of the skin and a greater
number of skin cancers.
CFCs
have been widely used as refrigerants (in fridges)
and aerosol repellents in deodorants and perfumes.
The use of CFCs has been severely
restricted in many countries
because of their damaging effect on
the ozone layer.
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