Lesson 2 unit 2 :Erosion of Ozone Layer and Global Warming (part1)

Erosion of Ozone Layer and Global Warming

Lesson objectives :

By the end of this lesson, the student must be able to :

1- Know the composition of Ozone gas.

2-Conclude the steps of ozone formation.

3- Appreciate the importance of Ozone Layer.

4-Describe the harmful effects of short- and medium-wave length ultraviolet radiation on the Ozone Layer.

5-Mention the pollutants of Ozone Layer.

6-Determine ways to protect Ozone Layer.

7-Describe the global warming phenomenon and the greenhouse effect.

8-Identify greenhouse gases.

9-Interpret the rising temperature of the earth’s atmosphere.

10Determine the negative effects resulted from the rising temperature of the earth’s atmosphere.

11-Follow up the procedures and solutions to the problems of erosion of the ozone layer and global warming.

First: Erosion of the Ozone Layer phenomenon

1-How ozone gas forms

 

*Ozone gas is formed in two steps:
1- breaking down the bond of oxygen molecule when it absorbs the ultraviolet radiation (UV), producing two free active oxygen atoms

2-Each free oxygen combines with an oxygen molecules  to produce  ozone molecule

3- Ozone layer is formed in the stratosphere, and is located at a height between 20:40 km above sea level. Ozone layer is the first atmospheric layer that meets the ultraviolet radiation coming from  the sun

• For more information about Ozone layer formation, please visit these links:

 2-Importance of Ozone Layer

Ozone layer does not allow penetration of all far and medium ultraviolet radiations, which have very harmful effects. That is why Ozone is said to act as a protective shield for living organisms against the harmful chemical effects of the ultraviolet radiation. 

For more information about Ozone layer importance, please visit these links:

•  Harmful effects of far and medium ultraviolet radiations

  
  1-Human

• 
  * Increasing the rate of skin cancer.
  * Cataract.
  * Weakness of the immune system.

2-Amphibians

* Spoil eggs.
* Decreasing rate of reproduction.

 3-Marine organisms

* Death of plankton which is the main nutrient of small animal creatures.
* Destroying the marine food chains.

 4-Terrestrial plants

* Upset the photosynthesis process.
* Shortage of crops production.

For more information about Ozone layer importance, please visit these links:

 

3-Erosion of the Ozone layer

1-Temperature and atmospheric pressure atOzone layer differ from those at earth’s surface.The English Scientist Dobson postulated that the thickness of the Ozone Layer is 3 mm only if it were under the normal pressure and 0º C temperature; a condition known as STP or standard temperature and pressure Accordingly, he assumed that the natural amount of ozone equals 300 Dobson units

2- Since 1978, scientists have noticed that there was erosion of the Ozone layer above the South Pole; phenomenon known as Ozone Hole, that increases in September each year –Why? Its rate changes from year to year

For more information about Ozone layer importance, please visit these links:

4-Pollutants of Ozone Layer

1-Chlorofluorocarbons (CFCs) 

*The most widely used ODS, accounting for over 80% of total stratospheric ozone depletion.
Used as coolants in refrigerators, freezers and air conditioners in buildings and cars manufactured before 1995.

 *Found in industrial solvents, dry-cleaning agents and hospital sterilants. 

*Also used in foam products — such as soft-foam padding (e.g. cushions and mattresses) and rigid foam (e.g. home insulation).
Halons 

*Used in some fire extinguishers, in cases where materials and equipment would be destroyed by water or other fire extinguisher chemicals. In B.C., halons cause greater damage to the ozone layer than do CFCs from automobile air conditioners.

2-Methyl Chloroform

*Used mainly in industry — for vapour degreasing, some aerosols, cold cleaning, adhesives and chemical processing.

3-Carbon Tetra chloride

*Used in solvents and some fire extinguishers.

4-Hydrofluorocarbons (HCFCs)

*HCFCs have become major, “transitional” substitutes for CFCs. They are much less harmful to stratospheric ozone than CFCs are. But HCFCs they still cause some ozone destruction and are potent greenhouse gases.

For more information about Ozone layer pollution, please visit these links:

Effect of CFCS compounds on the Ozone Layer:

• First step: Ultraviolet radiations (UV)break down the chlorofluorocarbon compounds and liberate active chlorine atoms Cl CFCl3

• Second step: Active chlorine atoms react with ozone molecules forming Chlorine monoxide

• third step: Chlorine monoxide react with the other ozone molecule when the other active Chlorine atoms liberate and play their role in destroying more amounts of ozone gas

For more information about Effect of CFCS compounds on the Ozone Layer:, please visit these links:

5-Protecting the Ozone Layer

Due to the serious situation of Ozone Layer, an international conference was held in Canada to discuss how to protect the ozone layer and take all suitable measures to solve this problem. They reached a group of recommendations called “Montreal Protocol” where it is signed by 191 nations.

For more information about protecting the Ozone Layer:, please visit these links:

For more information about  this lesson:, please visit these links:

*These is flashes talking about the lesson: