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Question: When is a hole, not a hole? Answer: When it is a hole in the ozone layer. The so called 'ozonehole' is not really a hole. It is just a region of the stratosphere where there is less ozone than normal forthat part of the stratosphere.
1. What do you already know about the hole in the ozone layer? You may recall, from FIGURE 2 on page 13 of the Introductory Lesson of E & B Instructional Module 5,that the stratosphere occurs between the troposphere and the mesosphere, extending from about 10 to 50km in altitude? Has anybody actually seen and photographed the bottom of the stratosphere? Isn't the stratosphere justthin air, so how could you recognise its bottom? Think about it.
2. How could you identify the bottom of the stratosphere? What would you look for? If you couldn’t answer Question 2, visit the web site whose Internet Address (URL) is given directly
below. The web site opens to reveal a magnificent panorama of the Moon above Earth, photographed
from space by the shuttle astronauts in 1990.
EB.IM5.L3 Atmosphere  M. J. McGarry (2000)
3. Just how big is the hole in the ozone layer? How big is the mean size of the ozone hole compared to the area of say Australia? Is the size of the ozone hole constant, or does the ozone hole size vary frommonth-to-month? Does the size of the ozone hole vary significantly from year-to-year? What do youthink? If you don’t know, how could you find out? Students in each Learning Group should now visit the web sites whose Internet Addresses (URL's)
are listed below to research the answers to Question 3.
4. If the size of the ozone hole varies from month-to-month, why does it? What atmospheric conditions and processes cause the size of the ozone hole to vary from month-to-month? Can you identify and
explain how these atmospheric conditions and processes combine to change the size of the ozone hole
over climatic time?
The answer to Question 4 is the subject of ongoing atmospheric research. In trying to answer
Question 4, you are exploring extremely up-to-date scientific information that you won't find in
traditional lower secondary science textbooks.
EB.IM5.L3 Atmosphere  M. J. McGarry (2000)
To successfully answer Question 4, you will need to understand how the combined effects of PolarStratospheric Clouds (PSCs) and the Polar Vortex lead to a reduction in stratospheric ozone, particularlyover Antarctica.
Polar Stratospheric Clouds (PSCs), also known as nacreous or mother-of-pearl
clouds, form during cold polar stratospheric winters, when despite the dryness of the
stratosphere, the air temperature drops low enough for condensation and freezing to
occur. They consist of a mixture of ice, nitric acid and other aerosols, which allow
ozone depleting chemical reactions to occur on their cloud particle surfaces.
You can judge for yourself, the beauty of mother-of-pearl clouds shown in photographs of them
displayed at the web sites, whose Internet Addresses (URL's) are listed below.
The Polar Vortex is a circular, downward-sinking whirlpool of stratospheric air that
occurs over the poles during the polar winter. The polar vortex is more pronounced
over Antarctica than over the Arctic Circle.
5. When viewed from above the South Pole, would the circumpolar vortex circulate in an anticlockwise direction or in a clockwise direction? Explain your choice of direction. Write your explanation onyour printed map.
Open web site #1 whose Internet Address (URL) is given below to print a landscape orientation
copy of the Antarctic Region map. On your printed map show the wind directions within the
polar vortex by drawing arrows.
For your interest, web sites 2 and 3 provide information of Australia's involvement in Antarctica.
EB.IM5.L3 Atmosphere  M. J. McGarry (2000)
Students in each Learning Group should now research the answers to
Question 4, from page 2, by visiting the web sites whose Internet
Addresses (URL's) are listed below.
6. Can you now explain the role played by polar stratospheric clouds in the depletion of ozone in the stratosphere above the poles, especially above Antarctica? To successfully answer this Question, youmust demonstrate an understanding of all relevant chemical reactions.
EB.IM5.L3 Atmosphere  M. J. McGarry (2000)
Students in each Learning Group may like, for interest only, to visit the
web sites whose Internet Addresses (URL's) are given below to see
computer simulation images of the polar vortex.
Stratospheric ozone occurs in a layer centred at about 20 to 25 km altitude, reaching a peak concentrationof about 10 parts per million (ppm).
Students in each Learning Group should now visit the web site whose Internet Address (URL) is
given below to view a graph of the variation in ozone concentration with altitude.
7. Why does stratospheric ozone exist in a layer, whereas the concentration of other atmospheric gases decrease exponentially with increasing altitude? To successfully answer this Question, you will needto consider those factors that limit the production of ozone at the top, and at the bottom of the ozonelayer.
Stratospheric ozone beneficially absorbs ultraviolet radiation of wavelength between about 200 to 290manometers (nm) referred to as UVC. UVC is extremely harmful to multicellular life forms includinghumans. The ozone layer effectively shields life at the Earth's surface from harmful UVC radiation.
8. When ozone (O3) is destroyed by chemical reactions it reverts to oxygen (O2). Oxygen (O2) evidently does not absorb UVC radiation as effectively as Ozone (O3) does. Can you explain why? EB.IM5.L3 Atmosphere  M. J. McGarry (2000)
9. Can you write chemical equations to describe the chemical reactions that produce and destroy Students in each Learning Group should now visit the web sites whose Internet Addresses (URL's)
are listed below to research the answer to Question 9.
It has been known since about 1974 that manufactured chlorofluorocarbon (CFC) compounds migratinginto the stratosphere deplete stratospheric ozone. Chlorofluorocarbon compounds, being fairly stablegases, were once used as propellants in aerosol spray cans, including asthma inhalers.
More and more children from around the world are being diagnosed as
asthmatics. These children manage their asthma by inhaling medication like
Ventolin. The CFC propellant that was once in Ventolin has now been replaced
with a 'non-CFC' propellant called hydrofluoroalkane (HFA).
Both HFA and CFC's contain fluorine atoms. Why then is HFA ozone friendly,
whereas CFC's are not? What is the chemical structure of HFA (or R-134a)?
EB.IM5.L3 Atmosphere  M. J. McGarry (2000)
Students in each Learning Group should now collaborate to produce a
group electronic report into all aspects of ozone depletion. They are to
confine their research to those web sites whose Internet Addresses (URL's)
are listed below.
10. Do you think that there is a connection between the hole in the ozone layer and global warming? If you think that there is, you must describe the connection?
EB.IM5.L3 Atmosphere  M. J. McGarry (2000)
Students in each Learning Group should now visit the web site whose Internet Address (URL) is
given below to check their answer to Question 10, from the previous page.
11. How is it possible that human-induced enhancement of the greenhouse effect causes heating of the
troposphere, and at the same time cooling of stratosphere, which results in more polar stratospheric
clouds leading to further ozone depletion?
REFLECT AND RE-LEARN
Students in each Learning Group should now reflect upon the core
content of this E & B Lesson by compiling an electronic glossary of key
terms / concepts (ideas), which were identified by them during study of
this E & B Lesson.
To compile your electronic glossary, identify by group consensus the key
terms / concepts.
You have now completed this E & B Lesson. Well done.
Should you wish to extend your understanding of atmospheric science
and climate, you could visit the web sites whose Internet Addresses
(URL's) are listed below.
EB.IM5.L3 Atmosphere  M. J. McGarry (2000)

Source: http://www.wqsb.qc.ca/mydestiny/Lesson%20Plans/More%20Activities/Earth&Beyond_m5_l3.pdf