Science Lesson: CO Buildup City

Time:	1-2 class periods (45 minutes)
Preparation Time:	5 minutes securing computer lab or setting up a Proxima or AverKey 5-10 minutes becoming familiar with simulation at http://www.airinfonow.org/html/activities.html
Materials:	Computer Lab Proxima or AverKey if lab unavailable Handout 1, handout 2, handout 3, (if you prefer students to follow one)
Teacher Preparation:	5 minutes

Abstract
During this lesson students will use a computer simulation to explain the relationship between city size, temperature, and air quality.

Purpose – To explain how city size, temperature, and pollution is related to the air quality.

Objectives
Students will be able to:

i. Conduct a controlled experiment.
ii. Collect data in an organized manner.
iii. Analyze data to reach a conclusion.
iv. Communicate findings.

National Science Education Standard:
Content Standard D - STRUCTURE OF THE EARTH SYSTEM

• The atmosphere is a mixture of nitrogen, oxygen, and trace gases that include water vapor. The atmosphere has different properties at different elevations.

Arizona Science Education Standards
Strand 6 - Earth Science
    Concept 1 – Structure of the Earth
        PO 1. Describe the properties and the composition of the layers of the atmosphere.
        PO 5. Describe ways scientists explore the Earth’s atmosphere.
Teacher Background
Whenever you burn fuel (like gasoline in your car), CO is produced. You may be breathing high levels of CO near busy roads and intersections. Other sources of CO include almost anything with an engine, power plants that burn coal, gas, or oil, and incinerators used to burn garbage. Inside your home, CO can come from your furnace or space heater, wood-burning fireplace, or from cigarette smoke. During the winter months more carbon monoxide is emitted into the air. This is because fuels burn less efficiently at cold temperatures. Also, the air is more stagnant in cold weather. When the air is stagnant, it doesn’t get as mixed up, so pollution may remain in one place.

Carbon monoxide causes more poisoning deaths in the U.S. each year than any other substance. When we breathe the air we take is typically a mixture that is predominately nitrogen and oxygen. The oxygen moves across the lung into the blood stream and is carried to the rest of the body by a delivery molecule called hemoglobin which resides in red blood cells. However, carbon monoxide has a greater affinity for hemoglobin than oxygen. If there is a lot of CO in the air taken in, it will supplant the oxygen within the hemoglobin carrier and consequently the hemoglobin will deliver less oxygen to the body. When exposed to high levels of CO, a person might notice shortness of breath or a slight headache. These symptoms will be more intense if the person is exercising, has a weaker heart or lungs, or has a respiratory disease like asthma.

Activity

1. As students enter the room, have the following question on the board. Students should write it and a response in the “if…then…” form of a hypothesis in their science notebooks. “What is the relationship between city size, temperature, and the amount of pollution?”

2. Ask students to share their ideas with the class, making sure that all hypotheses have an explanation for their ideas. (Quality hypotheses will refer to the previous lab results.)

3. Tell students they will be visiting the computer lab today (and possibly tomorrow). While they are there, they will conduct a controlled experiment to see how different variables affect the amount of pollution or air quality. The better the air quality, the lower the numerical value.

4. Take students to the lab and have them open the CO Buildup City flash animation from Air Info Now at http://www.airinfonow.org/html/activities.html

5. Allow students a few minutes to become familiar with the program before getting to work. This will maximize their on-task time during the experiment.

6. Once students are familiar with the program have them design an experiment that will test the effects of only one of the two possible variables (time of day and city size). Students should write up their procedures and design a data table before beginning.

7. Once the procedures and table are complete students may begin. (see Size Protocol and Time Protocol for protocol for both experiments as well as possible data charts)

8. When they have finished collecting data, have students write a formal conclusion in their science notebooks. What did they discover? What was the relationship between the independent and dependent variable?

9. Students can now go back and repeat steps 6-8 controlling for the other variable. This will give them a complete picture. If you are pressed for time, you might elect to have half the class control for temperature (time of day) and the other half control for city size (amount of CO released into the air). Advance groups might carefully control both variables simultaneously.

10. When students have completed both experiments, bring them back together in the science room. Have students share their findings. Did all groups agree about what was causing their results? Why?

11. Ask students to relate their findings to asthma. What size city is best for a student with asthma? Why? When is the safest time of the day to be outdoors? When is the most dangerous? Why?

Extension
Have students write a brief paragraph about how they, or their families, could help reduce their personal CO emissions.

Embedded Assessment
Students’ hypothesis development can be assessed by their hypotheses in the notebook. Their ability to recognize and manipulate variables in a model can be assessed. The ability to write a conclusion and apply their understanding to another situation can be assessed via the questions at the conclusion.