#2 – Why we use film canisters to teach scientific method (and why you should too)

What do we tend to focus on when we teach scientific method? Part of “doing” science is to come up with models that describe invisible phenomena. Bohr, Rutherford, and Thomson developed models of the atom. Watson and Crick developed the double-helix model of deoxyribonucleic acid (DNA). However, when we teach scientific method, we don’t always address this aspect of science. So, how do you teach this process? How do you teach students how to “do” this type of scientific research/thinking?

Too often, we associate “doing” science as just doing the the scientific method. More specifically, when we teach scientific method, we tend to focus on controlling and changing variables. It’s not. Science is also about analyzing and drawing inferences from data to come up with a conclusion. It’s about coming up with an explanation for what is going on – both seen and unseen. So, while making paper airplanes and adjusting their designs over and over may be a good way to quickly teach students to draw conclusions from something they can see, it does little to teach students about explaining the unseen.


A New Lesson from Old Technology (the film canister)

Using film canisters, I redesigned the classic Mystery Box Lesson to teach students to develop models to explain invisible phenomena. I use this when I teach scientific method. At the end of the post, you can sign up to get a copy of the handout I give to students emailed to you.


When I was going through the teacher education program at the University of British Columbia, I remember an activity where we were expected to develop a model for what was happening inside a black mystery box. The instructor would pour a clear, colourless solution (water, we thought) into an opening at the top of the box. A coloured solution would then exit an opening on the bottom of the box. Sometimes the solution was green or red or blue or violet. The colours changed each time more colourless solution was poured through the top. I never did find out what was happening inside the box (and to this day, I can only guess that acid-base indicators were at play). But, when I started teaching my own class, I wanted to reproduce the same experience for my students. That’s when I stumbled upon some black film canisters in our lab.


Set up & Notes from the field

Film canisters are awesome in so many ways: they’re durable, reusable, cheap (they can be free if people haven’t gotten rid of them already) or cheap to acquire, and they can be sealed. I opened a black film canister and filled it with a thumbtack, penny, and a cotton ball. I put the cap back on the film canister and wrapped the top with tape. This sealed, black film canister is my students’ mystery box.


My students need to determine what is inside the contents of their mystery box. They’re allowed to shake and play with the mystery box anyways they see fit. They drop it from different heights, roll it at different speeds. Anything (so long as they don’t destroy the mystery box or open it up). And, they end up finding different ways to interact with their mystery boxes to create different sounds. I provide students with empty film canisters and a variety of small materials – macaroni, staples, thumbtacks, cotton balls, pennies, marbles, etc – and I have them create an identical model (ie. replica) of their mystery box. It’s a lot of fun, and the students are certainly engaged with and excited about the challenge.


After 20 minutes of experimentation, we debrief the activity. We go over what they claim to be in the mystery box and what evidence supports their claim. After some discussion, we open the mystery box. This is generally followed up by a whole bunch of “I knew it”s.


Some useful tips

If you plan on doing this activity, consider the following:

  • Use opaque film canisters.
  • don’t fill the film canisters to the brim. Things have to be able to move in the mystery box or else it will be too challenging for the students.
  • have students write down why they believe a certain piece is inside the mystery box. When asked why a student believes a penny is inside the mystery box, they might say “because it sounds like a penny.” Follow up by asking, “what exactly does a penny sound like and how did you come up with that conclusion?”
  • I usually tell students that there are at least 3 items in the mystery box.
  • this would be nice activity to use CER (Claim, Evidence, and Reasoning).
  • as an extension, you can ask students what else can be done to determine what is inside the mystery box besides shaking the box. Students will say x-rays, but have students explore other methods. For example, some students propose weighing every piece separate and then putting different combinations of pieces together before they get the same mass as the mystery box.


Putting it all together

Making models to explain a phenomena is an important science skill. It’s also necessary to address it when we teach scientific method. And, there are better ways of doing it besides making models of the solar system or eukaryotic cell. Using film canisters to create mystery boxes is our cheap, easily accessible and highly engaging solution. If you’re interested in getting a copy of our step-by-step student handouts emailed to you, join our email list by clicking on the link below. You’ll receive also receive our e-newsletter as well as any other free resources we develop in the future.


Grab the Activity handouts by clicking here!


Until next time, keep it (ie. science) REAL.


Posted on August 6, 2017 in Activities

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