Students use the engineering design process to design a low-tech particulate matter detector. They test out their models, and then deploy them into the field where they can gather PM that is deposited. Next, they gather and analyze the data from their detectors in order to support claims about how safe the air is around the school.

Approximate Time: 3-4 class periods (180-240 minutes)

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Objectives:

• Students will be able to design, test, and deploy particulate matter collectors

• Students will be able to collect and analyze data to determine what areas of the school community have high levels of particulate matter in the air

Materials:

• Magnifying glass or dissecting scope

• Graph paper

• Materials for building the detector (see note below)

• Materials for testing the detector (ex. flour and pencil shavings)

• Scissors

• Additional paper for students to brainstorm and design

Handouts:

• Design A Particulate Matter Detector

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DCI: LS2.C: Ecosystem Dynamics, Functioning, and Resilience

DCI: ETS1.B: Developing Possible Solutions

SEP: Designing Solutions, Analyzing Data

What sources of particulate matter do you think there are near our school? (you can be broad with the definition of “nearby”)

• Possible answers: schoolbuses (and other vehicles), construction sites (for dust), power/chemical plants that are upwind, wildfires, fields/trees that are producing pollen

Tell students that now that they know the trucks in the pictures are emitting particulate matter, as citizen scientists it is their job to see if trucks or other sources of PM are making their own communities unhealthy. During the next few days, they will design, test, and deploy devices to measure the amount of particular matter in their school community. Measuring the amount of PM in the community is very important to know whether people’s health might be harmed from this type of air pollution.

Hand out the “Design a Particulate Matter Detector” sheet to students, and read the problem and goal together with them. Make sure all students understand the purpose of the challenge. Next, review the criteria for the detector (A successful device must…)

• Collect visible particulate matter (PM 10)

• Limit the amount of non-particulate matter collected (ex. hair and dirt)

• Include a method for measuring or counting the amount of PM collected (ex. using a magnifying glass and a grid for sampling)

• Be able to survive intact outside for at least 2 days on its own

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Next, review the constraints for this challenge (A successful device can only…)

• Use materials provided by the teacher or ones you can get from home

• Take no more than two periods to build prototypes, test, and create TWO identical final versions for use in monitoring

Take any time as necessary to answer students’ questions about the criteria and constraints.

Explain to students how their monitors will be tested before being used in the field. There are several options you can use based on available materials, but in general, they should involve dropping sample particulate matter (ex. chalk dust or flour) on the detector, along with larger debris (ex. pencil shavings). A successful test means the flour gets in, the shavings are kept out, and there is a way to measure how much flour is on the monitor.

Discuss the list of available materials with students, and review any additional rules for what students may bring in (ex. can they buy materials or do they have to be things they can find around the house?). Common materials students may want to use for their detectors are: paper plates, cardboard boxes and tubes, tape (regular and double-sided), petroleum jelly, string, glue, graph paper (to measure PM), note cards, duct tape, coffee filters, popsicle sticks, and pipe cleaners.

Form students into pairs, and have them begin by brainstorming different ideas for their designs on their handouts. if you think students will have a difficult time getting started, do this brainstorming as a class first. A good way to get students started is by having them think about how they can get the PM to stick to the detector. Write down options on the board.

Once students have a good set of ideas brainstormed, have them start designing their PM detectors on their sheets. Each part of their design must be labeled, and the design must address each aspect of the criteria. For example, make sure students have a way to sample the amount of PM (without trying to count it all) by using a grid. Check student designs and provide feedback. Try not to be judgmental – even if you think something won’t work, let students try so they can learn on their own. Also make sure that students have written a way to measure the amount of PM in their monitor on their handouts. Suggested methods include putting a grid under their “sticky” material so they can count/measure the amount in a few grids as a sample. When a design looks good, allow groups to begin building prototypes.

When a group has an approved design, they can take materials and start building. Be sure to control access to resources so one group doesn’t take too much of one resource (see modification note on budgets for an option on how to do this).

As groups finish their prototypes, have them test using whatever protocols you have established. For example, shake flour through a sieve from 12 inches above the detector, and sprinkle pencil shavings from 12 inches above the detector. See if the prototype can keep the non-PM out and allow the PM in. Also check if students can count/measure the amount of PM in a quantitative way.

As students make improvements to their designs and prototypes, support them by giving feedback and keeping them aware of time constraints. Try to avoid making suggestions, and instead ask questions to drive their design thinking. For example, “What materials could you use to help keep dirt out of the detector?” or “How can you use a grid to allow you to sample the amount of PM in the detector instead of counting it all?” or “What can you use to keep your detector from blowing away?”

Once students have reached their final products, have them create two identical versions. This will allow them to compare results from two different locations in a valid way.

As a class, choose locations around the school where the monitors will be placed. Try to avoid having the same pairs in the same locations (ex. If group A has their monitors in locations 1 and 2, then group B might have their monitors in locations 1 and 3). There should be at least two groups at each location to assist with comparative data analysis (see below). Have students record their locations on their handouts.

Put monitors out in their designated locations, and attach signs nearby indicating what they are and not to leave them alone. If you are concerned that monitors may be damaged by students, weather, etc., consider ways to avoid this, for example by putting them on a roof or on a high ledge. Leave monitors for at least one day. Check on them after 24 hours to see how they are doing. If results seem viable, bring them in; if not, try waiting an additional day or more. You can continue with the next activity in the meantime.

Once monitors are ready to be analyzed, bring them back to the classroom and have students measure the amount of PM in each monitor using the method they have determined. While these measurements may not be completely accurate, they should be able to determine which of their two locations are better or worse in terms of PM.

Share data across groups to determine an order of best to worst location (see note on comparative data analysis). It may help to have students write their data on note cards so these can be sorted by location. Have students record the class data on their handouts.

Have students answer the analysis questions on their handout based on the class data. Lead a short class discussion to clarify student thinking, with a special emphasis on where they think the PM in their school community is coming from.

Have students answer the Claim-Evidence-Reasoning prompt on the last page of their handout. An example response might be:

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• Claim: The air near the bus drop-off is the least healthy for people to breathe, and the air at the playground is the most healthy.

• Evidence: Monitors at the bus drop-off collected the most particulate matter compared to the other monitors around the school. Monitors at the playground collected the least.

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• Reasoning: If you breathe in high amounts of PM 10, it can get into your lungs and make breathing difficult. Because we collected the most PM 10 at the bus drop-off, that means the air there is the least healthy. We collected the least PM 10 at the playground, making the air there the most healthy.

Have students reflect on the project, either through writing or discussion. If you took pictures during the project, share them with students. Some useful questions to ask are:

• What did you like most/least about this project?

• Was this project fun? Why or why not?

• Did you ever get frustrated by your design? If so, how did you overcome your frustration?