Introduction: Air Quality Classroom Experiment
This experiment is a great introduction to air quality and particulate air pollution. Set-up is easy, and material cost is low- you can obtain everything you need for under $5 for a classroom of 30.
In this classroom experiment, you will use graph paper and petroleum jelly to "catch" particulate air pollutants for classroom observation. Each student group will be responsible for creating 3 Sample cards and placing them at various locations. At the end of the experiment period (24 hours) groups will collect the cards, observe, record, and analyze the pollutants collected.
Step 1: Materials
For this experiment, you will need the following materials (per group)
- Graph Paper (x3)
- Solid backing for graph paper- we used index cards. Cardboard or even plywood can be a great choice for outdoor locations
- Petroleum Jelly
- Plastic knife
- Binder Clips
- Magnifying Glass
Step 2: Trim Graph Paper
First, you will want to trim the graph paper so that it fits on your backer card without overlapping the edges.
Depending upon the age of your students, you may choose to adjust what size graph paper you use in order to facilitate the math in obtaining averages. For our experiment we used 14x14 graph paper. For younger students, you may want to use larger 8x8 squares
Step 3: Mount Paper to Backer
Next, you will mount the graph paper to the backer card. If you're using thin cards, small binder clips work well to mount the paper. You want to ensure that the clips do not cover any of the squares of the graph paper.
On the back of each sample card, write the location of where the card will be placed as well as the name or group number of the students.
Step 4: Coat in Petroleum Jelly
Next you will want to cover the entire section of graph paper with a layer of petroleum jelly. You want this layer to be thick enough to catch pollutants without being so thick as to obscure the lines of the graph paper.
Step 5: Place Sample Cards
Now you will want your groups to determine where to place their cards. This experiment works best with a range of indoor and outdoor locations. You will catch the highest amount of particulate matter if you have access to a heavily traveled street or highway where you can mount some of the cards.
When mounting in outdoor areas with heavy traffic, we recommend using wood backers, and mounting in the ground with a dowel rod.
After mounting the sample cards, leave them undisturbed for 24 hours in order to collect particulate matter.
Step 6: Retrieve Sample Card and Analyze
After 24 hours, retrieve the sample cards. In groups, have the students observe the particulate pollutants trapped on the cards. Have them count the number of particulates in each square of the graph paper, and record them in a table laid out with the same number of squares as the graph paper.
After all particulates have been counted, have them calculate the average number of particulates per square to be used while comparing pollution with other groups.
After all groups are done recording data, have them discuss their findings.
Which areas had the highest pollution?
Are they surprised by any of the sample cards (more or less pollution than expected?)
Does the pollution outdoors look different than the pollution indoors?
What are some similarities between the indoor and outdoor cards?
Participated in the
Paper Contest 2018
9 months ago on Step 6
The instructions above state the following: "After all particulates have been counted, have them calculate the average number of particulates per square to be used while comparing pollution with other groups."
From a pedagogical perspective, it would be ideal if students were able to gain an understanding of the purpose/value of calculating an average through this exercise. If students are going to be made to do that calculation, it should be in a situation that demonstrates a legitimate reason that people (e.g., scientists) would need to calculate an average in the real world.
However, in this activity, the students are all using identical grids for their data collection and tabulation: The grids all have the same size of individual squares and same number of squares. Thus, a comparison of each group's total count would be equivalent to a comparison of each group's average per square. In this type of study, using a grid facilitates the process of gathering data, but beyond that, there is no rational motivation for calculating an average per square after the total number of particulates has already been counted. It seems to be nothing but busywork in this case. Thus, students may get the impression that calculating an average is merely an annoyance that has no obvious purpose.
HOWEVER, if (for whatever reason) the groups were using grids that had the same size of individual squares but different numbers of squares, then it would be necessary to calculate an average per square before making comparisons among samples. In such a scenario, the value in calculating an average might be more apparent.
If the groups were using grids that varied not only in the number but also in the size of the squares (for example, if each group independently found their own grid to use online), then each group would need to calculate an average particulate count per unit area of their grid (e.g., average number of particulates per square centimeter) for any inter-group comparisons to be meaningful.
I've provided an example in the attached image, with commentary below:
Group A and Group B:
The comparison of the total counts (57 versus 21) is equivalent to the comparison of the averages per square (3.6 versus 1.3). In both cases, the measured particulates for Group B were 37% of the level for Group A. Another way of expressing this is that the measured particulates for Group A were about 2.7 times the measured particulates for Group B. Nothing is gained by doing one of these comparison versus the other.
Group C and Group D:
Here, the grids have different numbers of squares (16 versus 9), but the individual squares are all the same size. Thus, it's not meaningful to do a comparison of the total counts, since one of the grids has more squares than the other one does. But in this case, calculating an average count per square is useful because it allows us to compare different samples. Thus, despite a large difference in the total counts for Group C and Group D (19 versus 11), we can see that the average per square is approximately the same for both samples (~1.2).
Question 3 years ago
please its urgent
Question 3 years ago
how the jelly seperates the pollutants form air???????
5 years ago
Sounds like a great experiment! How did the classroom's air checkout?
Reply 5 years ago
The last time we did this with a school group, the classroom air was pretty clean. The card we put out in the parking lot near where the buses idle before school dismissal however, was a different story!
Reply 5 years ago
Yikes! I can imagin :P
5 years ago
In our area with spring showing up early the pollen is through the roof. I bet the pollen alone would cover one of these air pollutant cards. Nice way to show the students what they are breathing.
Reply 5 years ago