Ozone Attack

Background

You've already learned in class that the substance known as ozone () can be found high in the stratosphere where it serves to protect the earth's surface from high-intensity solar ultraviolet radiation. You've also learned that ozone can be found near ground level, a product of chemicals that comprise 'smog.' As a component of the lower atmosphere, it can cause significant damage to living things and some man-made materials.

Simple rubber bands, under tension, can indicate the presence of ozone. Because ozone attacks and weakens the molecular bonds between the molecules that make up rubber, the bands become cracked and brittle upon exposure to ozone. In this investigation, you will use the degradation of rubber bands as an indicator of ozone as you survey areas for the presence of ozone.

Procedure

1. You will be provided with a standard set of rubber bands and objects to stretch and hold the bands. (SEE NOTE #1 TO TEACHER)
   
   
2. Working alone or with a partner according to your teacher's directions, think about where you might expect to find high ozone concentrations and why, based on what you've learned about ozone. Develop a plan to determine whether or not these areas have high ozone concentrations as compared to other areas of potentially lower ozone, using the rubber band tests. In designing the study you will have to decide how long to run the test, where to place the rubber bands, and how you will measure and compare any possible ozone effects on the bands. In all these studies, be sure to only place the bands in shaded locations. If exposed to the sun, the direct action of solar UV on the bands can cause damage that resembles ozone damage. In order to design a good investigation, remember to always set aside one (or more) rubber band tests to be placed in an area of certain low (or zero) ozone concentration (in a zip-lock bag in a dark cupboard, for example, or sealed in a bottle with some activated charcoal to absorb any ozone that may be present in the air).
   
   
3. Show your experimental design to your teacher for approval before you proceed, then carry out the experiment, taking careful notes on what you do, how you do it, and the data that you collect.
   
   
4. Report the results of the study according to your teacher's instructions.

Observations and Questions

1. Make drawings and a table describing the observable changes in the rubber bands.
   
   
2. Which location showed the greatest changes? Which location showed the least changes?
   
   
3. On which day did you first see noticeable changes?
   
   
4. Did all the rubber bands change on the same day?
   
   
5. What do you think may have caused the change in the rubber bands?
   
   
6. What might explain why you observed different degrees of change in various locations?
   
   
7. What do you think the effect on the rubber bands might suggest about any possible effect of ozone on living tissue, such as plants or your own lungs?
   
   
8. Describe in a short paragraph why your data might suggest possible hazards to people who work in copy rooms.
   

When you're finished with the activity, click on Back to Teacher Guide at the top of the page.