Summary

In this lesson, students will develop an explanation for the consequences of ozone depletion on Earth by planning and carrying out an investigation. Students will use analysis and interpretation of data to develop a model to explain the cause and effect of Ozone depletion on the planet Earth.

Grade Level

High School and Middle School

NGSS Alignment

This lesson will help prepare your students to meet the performance expectations in the following standards:

• HS-PS4-3: Evaluate the claims, evidence, and reasoning behind the idea that electromagnetic radiation can be described either by a wave model or a particle model, and that for some situations one model is more useful than the other.
• Crosscutting Concept:
  • Cause and Effect: Mechanism and Explanation
• Scientific and Engineering Practices:
  • Developing and Using Models
  • Analyzing and Interpreting Data
  • Planning and Carrying Out Investigations

Objectives

By the end of this lesson, students should be able to

• Plan and carry out a controlled experiment to test a question.
• Analyze and interpret data.
• Describe the meaning of the Ozone Layer.
• Explain the relationship between light and the ozone layer.
• Using evidence, develop a model suggesting what will happen to life on the planet Earth if the ozone layer continues to deplete.

Chemistry Topics

This lesson supports students’ understanding of

• Energy
• Electromagnetic radiation
• Electromagnetic waves
• UVA, UVB, UVC
• Absorption
• Ozone Layer

Time:

Teacher Preparation: 30 minutes

Lesson: ~90 minutes (depends on teacher choices)

Materials (per lab group)

• Copies of the ChemMatters article, “The Ozone Layer”
• Light Source (flashlight or cellphone light)
• Ruler
• Masking tape (to hold the light source and light sensor distance constant)
• Paper
• Pencil/pen
• 8 squares of tissue paper sized 8”X8” (prefer light blue, light green, orange, or red)
• Interface (recommend LabQuest)
• Light Sensor (for settings see Teacher Notes: Explore section)
• Graphing paper or Graphing program
• Sticky Notes

Safety

• Do not shine light directly in your eye.

Teacher Notes

Engage

• Handout the “Engage” worksheet to all students in the room.
• Teacher: “Let’s think about this video and see what kind of sense we can make of it.”
• Show students the following video: Ozone Watch
• Teacher:
  • What do you see going on here? The Earth is spinning, and the thickness of the Ozone changes with time.
  • What do you notice when time lapsed happened? The Ozone layer disappeared over Antarctica.
  • When or where does this occur? It occurs from September to December in 2015 over Antarctica.
  • (Depending on student responses, you may have to explain the green and yellow colors are the Ozone Layer.)
• Teacher: Establish agreement about what whole class has observed. “OK so we agree that …”
  • Students should agree that the Ozone Layer disappears for a few months.
• Listen for students to make connections to what they’ve experienced.
• Teacher:
  • What are some things that you are not sure about here?
  • How could we test our hypothesis?
  • Use probing questions to lead students in the direction of light, the purpose of the Ozone layer, what types of measurements could we take to test the amount of light? What could we use as the Ozone Layer?
  • What kinds of information or experiences do we need to learn more?

Explore

• Provide students with the Experiment Development Tool handout.
• Give student groups a light source, ruler, masking tape, 8 sheets of tissue paper measuring 8”X8”, LabQuest, and light sensor.
• Teacher: Have students look through supplies, and ask any questions that they might have about the supplies.
  • The research question should have an independent variable of number of sheets of tissue paper, and a dependent variable of amount of light.
• Teacher: Develop an experiment that has one independent and one dependent variable. These questions will scaffold student thinking, and help students easily develop a step-by-step procedure. Here are some must have questions that we need to answer:
  • What observation can we measure? The amount of light with the light sensor.
  • What are we changing? We are changing the number of pieces of tissue paper in front of the light.Therefore, this is the independent variable.
  • What will we measure? We will measure the amount of light with the light sensor.
  • What is the purpose of that measurement? The purpose of the experiment is to see how the amount of light varies as the number of sheets of tissue paper increases.
  • How is light related to the ozone layer and UV light? The tissue paper is acting as the ozone layer, and the light from the flashlight is the UV light. We are testing what the Ozone Layer does with UV light.
  • What is going to stay the same throughout the experiment? Several things are going to stay the same throughout the experiment. The things are: distance between the light and tissue paper, distance between the tissue paper and sensor, the type of tissue paper, the thickness of the tissue paper, etc.
  • What is the control? The amount of light with zero sheets of tissue paper in front of the light.
  • What are we hoping to discover? The amount of light traveling through the tissue paper decreases with an increase in the number of layers of tissue paper.
• Lab Tips:
• Each lab group needs to find the answers to the questions through collaboration between the partners.
• Check each lab groups IV, DV, Constants, and Control. Help students use the answers to these questions to develop a step-by-step procedure.
• Students write a step-by-step procedure for the investigation of how the amount of light depends on the number of sheets of tissue paper present.
• The distance needs to be constant, and the paper needs to be placed directly in front of the light source.
• Students should not shine the light directly in their eyes. Do not use a black light unless students have the proper eye protection.
• Students need to set up a data table with at least 3 trials.
• Once the procedure is approved by the teacher, students can carry out the investigation noting the values on their data tables.
• The sensor sensitivity may have to be adjusted based on the type and brightness of the light that you are using.
• Students should graph their results and look for a pattern. The amount of light decreases as the number of pieces of tissue paper increases. The tissue paper is absorbing the light, just like the ozone layer absorbs UV light.
• Students should answer their research question in the on the experiment development tool page in the CER box.
• They should also answer the analysis questions on the back of the Experiment Development Tool page.
• You will have to post the analysis questions separately for students, because we do not want to take away from their discovery.
• For differentiation purposes, an optional lab handout has been included for teacher consideration/use which includes precise lab protocol.
• The color of the tissue paper does affect the amount of transmitted light. The darker the tissue paper the fewer layers of tissue paper. For best results use light blue, light green, orange, or red tissue paper.

Explain

• In partners, have students make a list of questions that they are wondering about based on their experimentation. The student questions are a formative assessment piece that gives you direction on what they currently know and what students would like to learn about the Ozone layer.
• Have students read the April 2013 ChemMatters Article, “The Ozone Layer: Our Global Sunscreen” and compete the Reading Strategy handout.

Elaborate

• Have students do a gallery walk quietly walking around taking time to read 1, 2, 3, contact on other students papers for 10 minutes. Students may want to take a sticky note with them to take notes.
• Reconvene discuss findings to the essential question: What is the purpose of the Ozone Layer?How does it function?
  Using questions such as: What is happening in terms of amount of electromagnetic waves and the amount of Ozone Layer?What did you discover?I heard these three hypotheses, which ones do you agree with based on your evidence? Alternatively, you could leverage everyday language: “I heard the use of the term electromagnetic waves.” Listen for partial understandings and alternative understandings.You may have to fill in some missed knowledge with a quick description.
• Distribute Show What You Know worksheet.
• Read the directions to the students and clarify any questions.
• Students develop models in pairs. A complete model must have all the “Gotta Have” points in the Checklist.
• Students share and discuss models, and update models using sticky notes.

References

Levy, Robert. “Ozone.” NASA, NASA, 30 July 1999, earthobservatory.nasa.gov/features/Ozone/ozone_2.php.

Newman, Paul A. “NASA Ozone Watch.” NASA, NASA, 18 Oct. 2018, ozonewatch.gsfc.nasa.gov/multimedia/index.html.

Windschitl, Mark, et al. Ambitious Science Teaching. Harvard Education Press, 2018.