Studying Ozone and Air Quality Steve Schneider Deborah Carlisle
Measuring Ground-level Ozone VOC’s + NOX + sunlight O3 Motor vehicles are the single largest contributor to ground-level ozone.
Measuring Ground-level Ozone O3 levels above 120 ppb are considered unhealthy. They can be generated by some electrical equipment or from photochemical reactions with smog: VOC’s + NOX + sunlight O3 Motor vehicles are the single largest contributor to ground-level ozone. In this project we are adapting the relatively easy-to-make Schoenbein papers for classroom use, and using ADI to analyze the color changes quantitatively.
Useful Sites • http://www.weather.gov/aq/sectors/nemetro.php#tabs • http://www.airnow.gov/
Findings: • Commercial cards had significant variability and were expensive. • Researched making Schoenbein papers • Inexpensive and safe to make
Schoenbein Papers Ozone was discovered by C.F. Schoenbein in 1839. He developed an ozone-sensitive test paper that was widely used historically, and more recently in classrooms. The standard protocol for using the papers calls for an 8-hour exposure to the air out of direct sunlight. Various studies have shown a dependence on humidity, and there are a variety of recommendations for moistening the strips prior to exposure. Control low O3 high O3 exposure exposure
History Despite the method's early limitations, starting in the mid-1800s, more than 300 stations recorded ozone exposures in countries such as Austria, Australia, Belgium, England, France, Germany, Russia, and the United States.
Learning Goals : • Analyze different relative amounts of ozone found in various locations using test results. • Understand that ozone is found near the earth’s surface (ground level) in the troposphere as well as the stratosphere. • Understand that ozone test strips/Schoenbien paper detect ozone gas through a chemical reaction that is caused by ozone in the air. • Use technology to more precisely analyze relative color changes obtained with ozone test strips.
Some Testing Ideas: • Test for ozone at different times of day and look for patterns. When are ozone concentrations the highest? • Test for ozone in various locations and see what areas are the highest. • Look at the effects of wind patterns on ozone • Students research and brainstorm where ozone might be found and what equipment/machines produce ozone
Classroom Use Made Easier: 1. Test strips can be stored in a double plastic zip lock bag, until you are ready to read your results. 2. To look at results simply dip your exposed test strip in a beaker of water. You will see a visible color change. 3. Compare the relative colors to the control. 4. Use digital analysis to measure RGB values and compare between test strips.
Testing Ozone Levels • Groups of 4 • Select a test site Things to Consider • Avoid direct sunlight • Free air circulation around your strip • Run a control with your group • Label an index card with date/time/location
Carrying Out the Experiment: • Discuss experimental design in your groups to come up with a plan for testing • Run tests (place test strips and control) • Collect test strips and place in zip-lock baggies • Return to lab and expose strips by dipping in water • Photograph test strips • Data Analysis and share results
How do Ozone Test Strips Work? Ozone is a strong oxidizer. It rapidly reacts with the iodide ion, I- in the KI salt applied to the filter paper. KI + H2O + O3 I2 + O2 + K+ I2 + I- + starch I3- + starch Last step : I3- (linear)+ starch (helix) (Turns Blue) Combination of I3- and helix causes light reflection to be in the blue/violet range of visible spectrum
Schoenbein Papers Cntrl 80 100 120 140+
National Science Education Standards • Science as Inquiry: Grades 5-8 and 9-12 Ability to perform scientific inquiry, understanding about scientific inquiry • Science and Technology: Grades 5-8 and 9-12 Understanding about science and technology • Science in Personal & Social Perspectives: Grades 9-12 Environmental quality, changes in environments