Name____________________________________
Environmental Science—Mr. Nelson
Battling for Oxygen Simulation
Introduction
Have you ever been sun burnt? How does this happen? Were you in the sun too long?
Ultraviolet rays from the sun cause damage to our skin, as seen by sun burns and sun tans.
Ozone is one barrier to letting those ultraviolet (UV) rays reach us on Earth.
When an ozone molecule absorbs UV light from the sun, it breaks down into an oxygen
(O2) molecule and an oxygen atom (O). Sometimes the oxygen molecule breaks into two oxygen
atoms as well. Normally, the free oxygen atom combines with other oxygen atoms or molecules
to produce ozone again. Under normal circumstances, ozone is continuously being destroyed
and regenerated by the sun's ultraviolet rays. When there are no outside disturbances, this
process of breaking down ozone and building it back up occurs at a constant rate that keeps us
protected from a lot the sun's harmful UV rays. However, harmful pollutants (such as CFCs
from aerosol cans) can also break down ozone by converting it into oxygen molecules and
atoms. When this happens ozone breaks down much faster than it can build up and "holes"
appear in the ozone layer. These holes are not actual holes, but areas where the ozone layer is so
thin that it lets more UV rays through. The air currents that carry the pollution determine where
the holes in the ozone exist.
Scientists and engineers have been measuring the ozone layer for many years, and
encouraging people to stop the destruction of the ozone layer by reducing the human-created
pollutants that contribute to its depletion. The most common ozone-destroying pollutants are in
a class of chemical compounds called chlorofluorocarbons (CFCs), which have been used in air
conditioner coolants and aerosol spray propellants. Today, many nations and industries have
taken steps, including the design of new technologies by engineers, to reduce the production of
CFCs and protect the ozone layer from harmful CFCs.
As pollution to the atmosphere increases, the amount of ozone decreases. In other words,
an increase in the amount of pollutants that reach the upper atmosphere disrupts the process
that makes ozone our safe protective shield. In today's activity, we are going to model just how
pollutants destroy ozone.
Set-Up

Make 100 gumdrop molecules, a mix of O2 (oxygen) and O3 (ozone) molecules (see
Figure 2). For an oxygen molecule, attach one gumdrop to each end of a toothpick. For an
ozone molecule, use two toothpicks and make the molecule in the shape of a "V." If you
have time, have the students make the molecules at the start of the activity.
Figure 2. Construction of oxygen and ozone molecules made with gumdrops and toothpicks.
DISCUSSION QUESTIONS
1. Who were the Ozone Makers?
2. Who were the UV’s?
3. Why didn’t any UV’s get to Earth during our first simulation?
4. Why didn’t the number of Ozone Makers grow with the number of CFS’s?
5. Where do the CFC’s go?