In This Activity, Students Will Observe How Ozone Can Damage Rubber Bands and Through A

Ozone Attack

In this activity, students will observe how ozone can damage rubber bands and through a comparison, they will be able to determine the relative ozone levels for different locations.

Background Ozone is present in the air that surrounds us. It is formed when hydrocarbons (HCs), Volatile Organic Compounds (VOCs) and nitrogen oxides (NOx) from forests, industries, and automobile exhaust react with heat and sunlight. This tropospheric ozone is often called "bad" ozone because it damages living tissue.

Some tropospheric ozone is natural. Lightning and static discharges are one natural source of tropospheric ozone. Ozone gives off the acrid smell after a lightning discharge. Some ozone is also produced when natural hydrocarbons formed by trees and other vegetation react with nitrogen oxides in the atmosphere and sunlight.

This activity is based on the high oxidation capacity of ozone, which causes rubber and plastic products to break down after relatively short exposure. By observing how rubber bands deteriorate and develop cracks or pits, the relative ozone levels can be determined for different locations.

Note: The xerographic process in most copy machines uses electrostatic charging of a cylinder. The accompanying ionization creates ozone in adjacent air, so a room containing a copy machine makes a good location for this experiment.

Learning Goals Students will be able to: 1. Identify that tropospheric ozone is often called "bad" ozone because it breaks down certain materials. 2. Explain that concentrations of ozone are not uniform. 3. Demonstrate that the longer the exposure to ozone, the greater the effect. Materials (per group of students)  3 glass jars or beakers  3 medium size rubber bands  Hand lens  Felt pen

Procedure 1. Place a rubber band around each glass jar or beaker near the center without stretching it very much. (The results of this experiment will be altered if the rubber bands are stretched a great deal.) 2. Write the group name, starting date, and location on a piece of paper and place it on the beaker or jar. 3. Use the hand lens to observe a section of the rubber band. Mark this section with a felt pen. 4. Make a drawing of this section showing the condition of the rubber band. 5. Place one jar outside away from direct sunlight. Place one jar in the classroom. Place one jar near the copy machine. 6. Observe and record (write and draw) changes within the marked section after one week.

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. What do you think may have caused the change in the rubber bands?

4. What might explain why you observed different degrees of change in various locations?

5. 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?

6. Describe in a short paragraph why your data might suggest possible hazards to people who work in copy rooms.