EXPLAIN THE THINNING OF THE OZONE LAYER

EXPLAIN THE THINNING OF THE OZONE LAYER

-          Depletion of the ozone layer (Region in the stratosphere between 20-25 km)

Able to explain what ozone is

·        Ozone is a molecule made up of three oxygen atoms//O₃

·        It is an (extremely) unstable molecule.

·        It forms a layer in the earth’s stratosphere (20-50 km from the earth’s surface)

                           

Able to explain the  importance of the ozone layer to humans.

It acts as a natural shield to protect the earth from ultraviolet radiation// It filters ultraviolet radiation so that only a small amount of it reaches the earth’s surface. 

Able to describe how the ozone layer becomes thinner

·        Thinning of the ozone layer is due to the widespread use of CFC/ Chlorofluorocarbon.

·        CFC is made up of carbon, fluorine  and chlorine

·        It is used in aerosol/ industrial solvents/as a coolant in air conditioners.

·        When ultraviolet rays strikes a CFC molecule (in the stratosphere), it causes a Chlorine atom to break away (from the CFC)

·        The free chlorine atom then collides with an ozone molecule and forms chlorine monoxide and an oxygen molecule

·        When a free oxygen atom collides with the chlorine monoxide molecule, an oxygen molecule and a free chlorine atom is produced.

·        The free chlorine atom then continues to destroy the ozone molecules

·        Each atom of chlorine can destroy thousands of ozone molecules.

-          Caused by Chlorofluorocarbons (CFCs)

-          CFCs sources: Coolant on air conditioners, Propellants in aerosol, Foaming agents (making styrofoam )

Able to describe the effect of the thinning of the ozone layer on organisms and the environment.

     

·        Causes an increase in the occurrence of cataracts and blindness.

·         An increase in the incidence of skin cancer.

·        Lowers the immunities against diseases/ lowers

      effectiveness of vaccinations.     

·        Ultraviolet radiation kills plankton in the sea. This affects the food chain of marine life

Ultraviolet radiation reduces the number of stomata and

• Affects : Skin cancer –melanoma
• Cataracts
• Sunburns
• Weakened immune system
• Lower the rate of photosynthesis, lower the crop yield
• Reduce nutrient contents (soya beans and peas) 
•         chlorophyll of the leaves of plants on land// This reduces the rate of photosynthesis in plants/ the productivity of the plant. Thus affecting the food chain .