Ozone Attack

In this activity, students observe how rubber bands deteriorate, developing cracks or pits, in locations with different ozone levels.

Learning Objectives

  • Students will understand that tropospheric ozone is often called "bad" ozone because it breaks down certain materials.
  • Students will be able to explain that concentrations of ozone are not uniform.
  • Students will be able to demonstrate that the longer the exposure to ozone, the greater the effect.

Materials

For each group of 3-4 students:

  • 3 glass jars or beakers
  • 3 medium-size rubber bands
  • Hand lens
  • Felt pen

Directions

  1. Have students work in groups of 3-4. Each group will have 3 jars or beakers and 3 medium-size rubber bands and will place each jar in a different location.
  2. 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.)
  3. Write the group name, starting date, and location on a piece of paper and place it on the beaker or jar.
  4. Use the hand lens to observe a section of the rubber band. Mark this section with a felt pen.
  5. Make a drawing of this section showing the condition of the rubber band.
  6. Place one jar outside away from direct sunlight. Place one jar in the classroom. Place one jar near the copy machine.
  7. Observe and record (write and draw) changes within the marked section each day for the next week.

Observations and Questions

  • Make drawings and a table describing the observable changes in the rubber bands. (Cracking or pitting of the rubber bands should be observed in some locations.)
  • Which location showed the greatest changes? Which location showed the least changes? (Answers will vary. Usually, the sample near the copy machine will show more changes.)
  • On which day did you first see noticeable changes? (Answers will vary depending upon the ozone concentration.)
  • Did all the rubber bands change on the same day? (Probably not.)
  • What do you think may have caused the change in the rubber bands? (Ozone will deteriorate the rubber bands at a rate dependent upon the ozone levels in the surrounding air.)
  • What might explain why you observed different degrees of change in various locations? (Hopefully, students will relate the amount of change to different ozone levels.)
  • 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? (Scientists are studying if there is a direct relationship between ozone levels and the amount of damage to biological materials.)
  • Describe in a short paragraph why your data might suggest possible hazards to people who work in copy rooms. (Scientists are trying to determine if high concentrations of ozone might be harmful to tissues of people working for long periods of time near copy machines.)

Extensions

  • Have students try different sizes of rubber bands, stretching versus not stretching the rubber bands, nylon stockings, different types of plastics, etc., at different locations, for different amounts of time. Students can look at differences in ozone levels at different street intersections since ozone is formed by the interaction of hydrocarbons and nitrogen oxides with sunlight. Students should keep a record of weather conditions, particularly sunlight, and level of air pollution during the recording time. The health department in some cities records pollution levels, including ozone levels.
  • Determine the economic impact of changes in tropospheric ozone. Things to consider: cost of ozone damage to materials such as tires, rubber, and plastics; costs and benefits of pollution mitigation.
  • Consider the impact ozone has upon society, for example, health care, crop damage, etc.

Example Lab Report Format

In this class, we will frequently be doing labs that you design and carry out on your own. For these labs, you will turn in a report, either on paper or on disk (your choice), that follows the following format:

TITLE: The title should specifically describe what the lab is about ("The effect of insecticides on plant growth," not "Chemicals and plants").

INTRODUCTION: Tell the reader why you are doing the study. Give enough background information so the reader will understand why the subject and the study are important. Tell the reader what you are trying to figure out in the form of a clear, logical, and answerable question.

MATERIALS: List all the supplies that you used so someone else could use exactly the same materials when repeating your study.

PROCEDURE: Pretend your lab is like a recipe and that you are writing for a reader not as smart as you. You have to describe exactly what to do and how to do it or the reader will probably mess it up. Procedures are best written in a numbered list (step 1, step 2, etc.) rather than in paragraph form, but if you like the paragraph form and can write very clearly, you may use it. If you've done it correctly, a younger student ought to be able to follow your instructions. Drawings or diagrams are often helpful. Be sure to identify CONTROL treatments and REPLICATES clearly in your procedure.

RESULTS: Data can take many forms, but it all needs to be clearly shown to the reader. You may use drawings, tables, or graphs, depending on what you are trying to show, but all have to be very well labeled, with titles and all units shown. You must also write in paragraph form what you found. This is where you draw the reader's attention to the most important or useful parts of your data. We will discuss these issues further in class.

DISCUSSION AND CONCLUSION: This is the heart of the lab! Plan to spend LOTS of time on this section! This section should be written in paragraph form, not in a list. There are several parts to a good discussion section:

  1. Summarize why you did the lab and how you did it.
  2. Summarize what you found.
  3. Relate your findings specifically back to your purpose or question. Did you fulfill the purpose, answer the question? (It's totally OK if the answer is no; many experiments don't turn out to be what we expect them to be.) Either way, explain why.
  4. Discuss sources of error: These are things that you couldn't control—faulty equipment, limits on time or resources, other things you didn't plan on. Don't just report that you messed up.
  5. If I wanted to pursue this research, what would you recommend that I do next? Leave me with a sense of where the research would go from here.

Background

Ozone is present in the air that surrounds us. It is formed when hydrocarbons (HCs) 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. Ozone has a high oxidation capacity, 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.

Learn more about ozone: