Lesson Notes By Weeks and Term - Junior Secondary School 3

DEPLETION OF THE OZONE LAYER

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TERM: FIRST TERM

SUBJECT: BASIC SCIENCE

CLASS: JSS 3

REFRENCES

    • BasicScience Made Easy for JSS Three by F.I Kehinde et al
    • BasicScience Made Easy for JSS Two by F.I Kehinde et al
    • STAN Integrated Science for JSS Three
    • Precious Seeds Basic Science for JSS three by J.O Otugboyegaet al.

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WEEK FIVE

TOPIC: DEPLETION OF THE OZONE LAYER

CONTENT

  • Description of Ozone Layer.
  • Importance of the Ozone Layer.
  • The hazards of Ozone Layer Depletion to Life.
  • Control Measures against the Depletion of Ozone Layer.
  • Global Warming.
  • Consequences of Global Warming.
  • Control of Global Warming.

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DESCRIPTION OF OZONE LAYER��

Ozone is a pale blue poisonous gas found in the earth's upper atmosphere. Ozone (O3) is a triatomic molecule of oxygen. It is stable than the diatomic oxygen gas (O2). It is present in low concentration in the troposphere. Ozone was first discovered by Louis Soret in 1865 and confirmed by Schonbein in 1867.

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The amount of Ozone in the atmosphere is measured in Dobson's unit.

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The stratosphere (upper atmosphere) has highest concentration of ozone to form what is called the ozone layer. The ozone layer is about 10km-50km above d earth surface.�

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Ozone is produced in the atmosphere by the action of ultraviolet ray from the sun on oxygen.

O2 �+ UV ----> 2[O]

[O] + O2 ----> O3

The ozone is destroyed by free oxygen atoms or elements that react with oxygen.

O3 + [O] ----> 2O2

The depletion of ozone layer simply means the continuous reduction in the amount of ozone in the atmosphere. Substances like chlorofluorocarbons (CFC), carbon monoxide (CO), nitrogen oxides etc, are responsible for the depletion of the ozone layer.

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IMPORTANCE OF OZONE LAYER

  1. Ozone is very important in the preparation of pharmaceuticals and synthetic lubricants.
  2. Ozone is used for bleaching substances.
  3. Ozone is used to kill microorganisms in water system.
  4. Ozone layer protect the earth from the heat of the sun.
  5. The ozone layer shields man, animals and plants from the harmful ultraviolet rays from the sun.

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INDUSTRIAL USES OF OZONE

Industrially ozone is used to:

  1. disinfectlaundry in hospitals and food factories.
  2. deodorizeair and objects especially after fire.
  3. assistin processing plastics to allow adhesion of inks.
  4. washfresh fruits and vegetable to kill yeast, mould and bacteria.
  5. manufacturechemical compounds.

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EVALUATION

  1. What is ozone layer?
  2. Briefly explain how the ozone layer is formed.
  3. What are the importance of the ozone layer.

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THE HAZARDS OF DEPLETION OF OZONE LAYER TO LIFE ON LIFE

  1. Exposure of the skin of man and other animals to the dangerous ultraviolet rays of the sun which can cause cancer of the skin.
  2. Depletion of the ozone layer allows more ultraviolet rays to reach us which may harm aquatic plants and animals thereby disrupting the ecosystem.
  3. Ozone layer depletion leads to the increase in the amount of greenhouse gases which� leads to excessive warming of the earth resulting to alteration of season.
  4. Depletion of ozone layer leads to global warming which contributes to flooding and other related hazards.
  5. Depletion of ozone layer in the lower atmosphere may lead to increase in toxic gases.

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CONTROL MEASURES AGAINST DEPLETION OF OZONE

  1. There must be regulation on the use of chlorofluorocarbons (CFC).
  2. There must be reduction of bush burning.
  3. There must be control of burning in household activities.
  4. Elimination of chemicals responsible for the depletion of ozone layer.
  5. Reduction of poisonous gases that can interact negatively with the ozone layer.
  6. Development of technology that will not emit dangerous gases from household equipments like refrigerator, air-conditioner etc.

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EVALUATION

  1. State five hazards that may result from the depletion of the ozone layer.
  2. State five control measures against ozone layer depletion.

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GLOBAL WARMING

Global warming is the increase in the average temperature of the earth over a prolonged period of time.�

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Two of the major causes of global warming are:

  1. depletion of the ozone layer
  2. greenhouseeffect (increase in greenhouse gases).

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Greenhouse effect is the reflection of radiant heat back to the earth as a result of accumulation of greenhouse gases (CO2, H2O CH4) in the lower atmosphere. The most important greenhouse gas is CO2. The increase in the amount of carbon dioxide in the atmosphere is a major cause of greenhouse effect and global warming.

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Sources of carbon dioxide in the atmosphere include:

  • burningof fossil fuels like coal, petrol, kerosene etc.
  • releaseof carbon dioxide from the exhaust of vehicles.
  • releaseof carbon dioxide from factories.
  • increasein population of man also contributes to the high percentage of carbon dioxide.
  • deforestation.
  • bushburning.
  • urbanization.

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CONSEQUENCES OF GLOBAL WARMING

  1. Seasonal/climate change.
  2. Rising oceans.
  3. Increase in flooding occurrences.
  4. Melting ice caps or polar ice.
  5. Increase in average temperature of the world.

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CONTROL OF GLOBAL WARMING

Global warming can be control through the following activities.

  1. Planting of trees will purify the atmosphere by absorbing carbon dioxide for photosynthesis and releasing oxygen which contributes to the formation of ozone layer.
  2. Reduction in bush and waste burning.
  3. Recycling of waste materials.
  4. Use of alternative energy sources other than fossil fuels e.g. solar power, wind turbine, water turbine.
  5. Electric vehicles should be used to reduce emission of carbon dioxide.

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EVALUATION

  1. What is global warming?
  2. State five sources of carbon dioxide to the atmosphere
  3. State five control measures of global warming

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GENERAL EVALUATION

  1. What is a machine?
  2. What are greenhouse gases?
  3. State five consequences of global warming.
  4. Explain why CFC is dangerous to the atmosphere.
  5. How can global warming be controlled.

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READING ASSIGNMENT

Precious Seeds Basic Science for JSS Three by J.O Otugboyega et al. Chapter 13 Pages 79-87

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WEEKEND ASSIGNMENT

  1. The major cause of greenhouse effect is the accumulation of� A. Water vapour� B. Carbon dioxide� C. Methane gas� D. Oxygen
  2. Which of the following is the chemical symbol of ozone?� A. O3 B. O2 C. CO2� D. H2O
  3. Which of the following is not a consequence of global warming?� A. Seasonal changes� B. Increase heat� C. Crop growth� D. Flooding
  4. Which of the following can cause ozone layer depletion?� A. CFC� B. Oxygen� C. Water vapour� D. Carbon dioxide
  5. Which if the following activities will help to control global warming?� A. Burning of fuel� B. Afforestation� C. Increasing human population� D. Urbanisation

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THEORY

  1. List five control measures taken to reduce the depletion of ozone layer.
  2. Explain the term "greenhouse effect".


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