Air pollution #3 – Building the idea of pollution caused by PM


Èlia Tena, Caterina Solé and Digna Couso


Universitat Autònoma de Barcelona

The aim of this activity is to help students gain an understanding of air pollution that is compatible with its scientific definitions. Specifically, it focuses on the understanding of air pollution as the presence of suspended particulate matter (PM) in the air. Students first analyse which pollutant is usually referred to by the media when describing urban air quality. Then, they carry out a learning lab activity exploring an analogy – they compare the pollution generated by an engine to what happens when a peanut is burned instead.


  • 12
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  • Air pollution


  • Between 1-2 hours

Students’ resources

Photos are shown to the students about what pollutants are usually referred to by the media when discussing air quality. Then, in groups, students need to compare the pollutants that appear in media reports with those that appear in their initial productions (drawing and descriptions of the previous activity), identifying similarities and differences. They also need to identify in which state of matter is the pollutant in our atmosphere. 

After a moment to share the groups’ conclusions, a lab activity is proposed to the students. An analogy is then proposed, between smoke from the industry, or a car’s exhaust pipe, and smoke emitted by burning a peanut or a piece of paper. Students then need to observe, on the one hand, that there are things that are invisible to the naked eye and, on the other hand, that after burning something, the air could contain small pieces of matter in suspension.

The scientific research question, materials, and the steps to conduct this lab activity are provided by the teacher. But the students must come up with predictions, their justification, collect data using a sensor and other observational methods, provide an the analysis, explanation of the results and conclusions.

Then, a video in which a scientist explains how he actually collects and analyses air pollution data in cities is shown to the students. 

Finally, considering all the activities done and conclusions obtained from the previous activities, students needs to write down their own definition of what a particulate matter (PM) pollutant is, including explicit references to its size.

Building the idea of pollution caused by PM

Teachers’ resources

Two different instruments to collect/analyse data of the smoke obtained from the burning peanut could be used in this lab-activity: a digital magnifier and a low-cost sensor.

Digital magnifier

Digital magnifier

Helps the students grasp the idea that although some particles might be invisible to the naked eye, solid particles from the smoke can be seen using a magnifier. It also allows the visualisation of particles’ approximate size.

Low-cost sensor

low-cost sensor

Helps the student to understand how many particles are created by burning an object, and their approximate size (10µm, 2.5µm or 1µm).


Particulate matter monitoring

To help students to understand the experiment proposed and the following activities, a video where a professional scientist explains how researchers collect data is shown.