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| Dallas Zoological Society Partnership : Elementary Fixing the Ozone Hole |
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Topic Overview
Quick Facts
Ozone contains
three atoms of oxygen rather than the two atoms we normally breath.
Most ozone (about
90%) resides in a layer that begins between 6 and 10 miles (10 and 17
kilometers) above the Earth's surface and extends up to about 30 miles (50
kilometers)
Stratospheric
ozone (sometimes referred to as "good ozone") plays a beneficial role
by absorbing most of the biologically damaging ultraviolet sunlight (called
UV-B), allowing only a small amount to reach the Earth's surface.
Because
tropospheric ozone (sometimes referred to as "bad ozone") reacts
strongly with other molecules, high levels of ozone at the earth's surface are
toxic to living systems.
Over some parts of
Antarctica, up to 60% of the total overhead amount of ozone
(known as the column ozone) is depleted during Antarctic spring
(September-November).
Human-produced
chemicals are responsible for the observed depletions of the ozone layer. The
ozone-depleting compounds contain various combinations of the chemical elements
chlorine, fluorine, bromine, carbon, and hydrogen and are often referred to as halocarbons.
Begin the Lesson
Extensive human use of
chlorofluorocarbons or CFCs in the 20th Century depleted the protective layer
of ozone in the stratosphere, which acts as a natural sunscreen for the earth
by absorbing most of the harmful ultraviolet radiation from the sun. Use of
CFCs has been banned in nearly all countries, but a significant level of the
remaining gasses will continue to rise to the stratosphere for the next 50
years. That's when researchers expect the earth's ozone layer to return to
pre-1980 levels. In this lesson, students will learn about the importance of
the ozone layer and discover ways to protect help protect it.
Whole Class Introduction to the
Lesson
You will need at least one
computer with Internet connectivity and a projection device, a classroom with
more than one computer, or access to a computer lab.� This introduction will take approximately 10
minutes to complete.
Introduce students to the subject
of the ozone layer by drawing a parallel between ozone and sunscreen. Activate
prior knowledge by asking students about their experiences with sunscreen and
sunburns.
Sample Questions:
Have your parents
ever made you put on sunscreen?
What did the
sunscreen do?
What can happen to
people who stay outside all day without wearing any sunscreen?
Explain to students that the
earth has a natural form of sunscreen called the ozone layer.
As part of the introduction, you
may want to review some of the glossary terms in advance of students going
online. At this point you can launch the WebLesson as whole-class activity
using a projection device, or you can assign students to work individually or
in teams in a computer lab.
WebLesson Sites
Introduction Bike helmets and knee pads can protect us from spills. Umbrellas can protect us from rain. Homes and school buildings can help us feel comfortable on hot or cold days. People need all kinds of protection.
Our planet has a layer of protection that keeps the sun's most dangerous rays from reaching us. It is called the ozone layer, and it is about ten to thirty miles above us in the sky. Without it, we would be in serious trouble. A few decades ago, scientists studying the ozone layer discovered that it was getting thinner. They even found a massive hole where the earth had no protection at all. Why was the ozone layer getting thin? What caused the hole? How big is it today? What are people doing to stop it? You will explore this scientific puzzle in this lesson, and you will find out how you can help protect the ozone. Scenario What would you say to someone who is damaging the ozone layer, especially if they don't know they are doing anything wrong? As you learn about the ozone layer and how important it is for all life on earth, think about ways that you can persuade others to help you protect it.
Lesson Pages
Ozone Hole
http://www.ace.mmu.ac.uk/kids/ozonehole.html
Hole in the Ozone Layer?
http://www.dnr.state.wi.us/org/caer/ce/eek/earth/air/ozonlayr.htm
On the Trail of the Missing Ozone
http://www.epa.gov/ozone/science/missoz/misspan.html
Doing Your Bit
http://www.ace.mmu.ac.uk/kids/doingyourbit.html Conclusion & Project
Conclusion NASA is keeping a close eye on ozone levels in the atmosphere, and also on the size of the ozone hole in the Antarctic. In time, ozone levels around the earth may get back to normal, and an ozone hole will not form. Many nations have already done their part by banning CFCs and reducing gasses that can destroy ozone. Are you willing to do your part by reducing pollution and using less energy?
Project Write a letter to the leader of any nation on earth that agreed in 1979 to ban the use of CFCs. Explain how you personally feel about the decision, and include some facts or statistics about what a difference it has made.
Glossary
atmosphere - a blanket of air around the earth
ultra-violet rays - invisible energy from the sun that can be harmful if people get too much
chlorofluorocarbons (CFCs) - a type of gas used by humans that can damage the ozone
ingredient - something used to make something else
polar stratospheric clouds - very high frozen clouds in the polar regions
molecule - the smallest particle of any substance
troposphere - the layer of the atmosphere next to the earth\'s surface.
humongous - really, really big
phase out - to gradually stop using something over time
plankton - tiny plants and animals that float in the ocean
compound - a substance formed by two or more ingredients
radicals - highly reactive molecules
severity - a level of seriousness, or a bad situation
fluctuations - changes from one level to another; always changing
greenhouse gas - carbon dioxide and other gasses that can lead to global warming
rubbish - trash, garbage
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