One of the best (and easy to implement) labs I do is an air pollution lab–airborne particulates lab (Click for student handout). I worked with a colleague at a neighboring school (Laura Solarez) to develop this lab for AP® Environmental Science. This lab works best in for unit 7 but really can be done anytime you can fit into your year. Click for an at-home version of this lab for virtual learning. 

This is an experimental design lab which is really important for students to do at least once or twice in the year, because the AP® Exam WILL have experimental design questions on the multiple choice section and on an FRQ. The AP® exam will ask complicated higher-level thinking questions-many of which are experimental design. 

Materials

Materials are quick and easy for this lab

1. Petri dishes-2 per student, if possible
2. Vaseline
3. Tape-blue painter’s tape is best as it can be removed easily to allow reuse of the dishes.
4. Stereoscopes are best. Microscopes can also work using a low objective. Hand lens with a good light source work, but are more difficult for kids to use. You can also use smart phone magnifiers plus light. 
5. Poster paper with markers (optional) for lab assessment

Day 1

Day one of the air pollution lab takes about 45-60 minutes. Student lab groups brainstorm and come up with a question to test, a hypothesis, and design. They must get two approvals from me before making their petri dishes.  My students have already done an experimental design lab so this process is fairly quick at this point. If this is the first experimental design lab of the year, expect this to take longer and for students to need more revision.

This lab is challenging with the constants. They can never really isolate all the variables and because of this, they will get flawed data. This is really important!!   Analyzing the weaknesses in their lab help them identify flawed experiments later on in life and on the AP® Exam. I aim to develop scientifically literate citizens.

I give students some ideas such as comparing indoor vs. outdoor particulates, front yard vs. back yard or the number of pets. Some students come up with very creative ideas outside of these suggestions.

If rain is in the forecast, make sure they don’t set out the dishes in the rain (or sprinklers). Also, they need to make sure they all set out the dishes on the same day for the same amount of time, because weather can influence.

After approvals, students make their dishes. I made this video last year. They pay attention to the video more than me demonstrating in person!  I show the video up to minute 3:18 on Day 1

Make sure you tell students to make a little sign at home, because I’ve had many dishes thrown away by parents over the years. They don’t know what it is and just throw away. Students make a sign that says “Science experiment–don’t throw away”.

Day 2 of the Lab

Day 2 of the air pollution lab is several days later. Give students enough time (over the weekend, for example) to expose their dishes for at least 24 hours. Students bring their dishes back to school on the day you instruct.

I show the rest of my video to help them understand how to count the particulates using stereoscopes. 

Students need to make a template out of graph paper to use on each petri dish. Its impossible to count every particulate so using a template with a few boxes helps them manage the counting.

Since students work in groups of 4, they divide up tasks. Some count data and some begin their posters. They can switch jobs if they desire.

After students finish counting particulates, They can wash the dishes in hot soapy water and dry. The dishes can be used again next year and also for the Soil Salinization lab.

Assessment

I like students to make and present posters for this air pollution lab. It really helps them discuss and analyze the results. Why their hypothesis was correct or not AND more importantly, why this lab was flawed. They can never fully control all the variables and I want them to see that other factors may have influenced their results. This is the best part of the lab–learning to identify flawed experiments.

My poster template is inspired by Argument-Based Inquiry, but I have added more sections and clearer instructions.

I have had students present to the entire class, present to two other groups, or make a Flipgrid. All three ways have merit.

You can also have students write a formal lab report individual or as a group as assessment as well.

Click for a poster rubric.

A complimentary lab is the Kill-A-Watt Lab.  A lot of particulates air pollution comes from the production of electricity from coal. This lab also helps students develop math skills.

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