Labs: Something I Want to Do Better

Whenever we enter the physics lab (really, it’s just the back half of my room so I’m talking metaphorically here), I feel the weight of big-S Science on my shoulders. I want to do it right. But I don’t know really what that means.

For one, I know a little about inquiry and know that I want some of that in my labs. Years of traditional education taught me that science and my own curiosity weren’t similar at all. You went in, followed some complex procedure and verified something you already knew and believed. Unfortunately for me, the verification and “proving” didn’t mean anything because the procedure shrouded all the real discovery in mystery.

For another, dispelling misconceptions seems like the most important work I can undertake as a science teacher. I definitely want some of that in my labs.

I think I’m improving at writing labs but they’re still unsatisfactory. Here’s my emotional laboratory roller coaster that often ends at unsatisfying:

I accept the challenge to write a lab that doesn’t feel like a waste of time and that kids actually learn from.

About the Lens Lab

Below is an optics lab I wrote with a colleague. We’ve already studied mirrors and done a little investigation with converging lenses. Kids know the mirror/lens equation:

My focus is on getting the kids to understand 1) the focal length (F) is a property of a lens independent of where you place an object, 2) when an object is placed at near-infinite distance from the lens, the image distance (di) equals the focal length (F), and 3) that the kids already know of real uses for lenses in different configurations. Do these goals come through in the lab?

I’m pretty happy with the final part (bottom of the last page).

Assume I’m not interested in a complete overhaul to modeling physics. What suggestions do you have to make my lab, or labs in general, better?

8 thoughts on “Labs: Something I Want to Do Better

  1. 1) Become interested in Modeling Instruction. 🙂

    2) In the meantime, have them decide what they can measure and how they can measure it. Have them use those ideas to decide on what relationship they are trying to find before they try to find it. Don’t put tables with headings into their work for them. Don’t give this all to them at once.

    Things like “What do you think I wanted you to learn from this?” encourage them to think of this as (at worst) the School Game (like one of the new students in my class was expecting to play—a couple of days ago she asked me, “If we get a decimal, that means we did it wrong, right?”— ….?!?!?!!….!), or probably at least like this is yet another version of “guess what’s in the teacher’s head”, when really (I think) you want them to be discovering relationships and building their own understandings based on the real world that they are existing in right now.

    Sorry if that’s a bit harsh. :/ I don’t mean it to be harsh, so much as just telling you what I was thinking as I read through the document.

    • 1) I haven’t ruled out modeling, just know that it’s not going to happen this year.

      2) How do you get that conversation going? (PS — I love your blogging style where you walk me through your questioning because it’s always very enlightening.) Maybe something like, “Hey, we have these lights and lenses. What do you think we can do with them? … Yeah, but what can we measure? … ”

      I wrote the lab out to give structure. Without structure, I fear the kids — and I — will flounder. Other than having the kids accustomed to modeling methods, how would you recommend I put some structure in place without being stifling. Because that’s precisely what I’m trying to avoid.

      Very fair criticism on the “guess what I was thinking” line. I was trying to get at “hey, isn’t it interesting that the focal length is the same in every case?” without coming right out and saying it.

      Gah!!!! on decimals. As a math teacher, that type of expectation was always very frustrating to me.

      Not harsh at all. 1) I asked for feedback. 2) Yours is completely reasonable. You should know by now that I appreciate your viewpoint.

      • The basic steps are:

        a) Show something cool (some phenomenon… a cart moving at a constant velocity or acceleration; a hover puck experiencing balanced and unbalanced forces; a lens, object, and source set up so that the object is focused on the screen; etc).

        b) Ask for observations. You’re not looking for anything specific. You’re just letting them get their brains going. Challenge observations (by putting it back to the group and/or by letting them observe again, this time for that specific thing) that conflict with each other (or that are obviously not true), but don’t try to push them in any specific direction overall.

        c) Now that they’ve thought about the situation a bunch, ask what they could measure and what tool they would use to measure it. Make a big list. Push them a bit if needed so all the things you want end up somewhere on the list. Don’t allow anything that you don’t have a tool you could use to measure it. Also, calculations aren’t measurements.

        d) Ask which of the things on the list are changeable. Which can you choose values for?

        e) Ask which of the things on the list depend on the things you can change.

        f) Cross off anything that doesn’t fall into those two categories.

        g) Use your designations to find pairs of things that you’d like to find the relationship between. Each pair is an experiment (keep everything else constant). Have them state out the objective of that experiment. Give them the lead: The objective is always “to find the relationship between…” In the end, you can find a way to combine all of the related relationships into an uber-relationship (like a vs m and a vs Fnet combining into N2L).

        h) They just invented the experiment! (Coincidentally, the one you wanted them to do all along… funny how that always works out.) They know exactly what they want to measure and how they want to measure it. They know what to put in a data table and what to graph when they are finished taking the data. You don’t even need handouts with instructions anymore. They just created the instructions. Celebrate. 🙂

  2. This looks great. One thing our science teachers do is have students design at least some of their own labs. By the time they get to 12th grade after they’ve been designing labs for themselves for 6 years or so, they are actually pretty good at it too. This way they see that science is a process they can control themselves.

    • Yes! That’s what I want! I have 9th graders who are new to this style of science. How do I start this training NOW? With optics?

      Help me out with the first steps? How do I get kids to ask a good research question then decide how to measure data to support their question?

      • I think that starting with questions students have and helping them design ways to answer those questions is a start. I don’t know how much the questions matter, although obviously some children will ask very simple questions or questions which are much too difficult to answer with the equipment they have.

        What process do you go through when you design labs? Modelling this approach with the students is probably a good start, although I rarely see science teachers have enough time to do this. The idea is, if the students see you design a lab along side them, they will have some understanding of what that process looks like. You can do this after they have made a first attempt in designing their own labs, or before hand, depending on the needs of your students.

        Another observation is that students rarely, if ever, get to see how a lab is refined. So for example, scientists spend a lot of time fixing mistakes in their lab process. I suspect it is rare that they get the expected results (if they have expectations, which I have read they often do not) and so they have to mess around with their equipment and their process until their experiment yields results. This is obviously time-consuming, but for simple scientific ideas, it is probably worth it.

        I have done student student-designed labs in optics, and I don’t remember them going particularly well for my students, but I think with iteration that improves to some degree. I think it’s also okay to work with students to improve their lab process as they are working on it, and to point out some flaws in their methodology, particularly if you have shown them how you sometimes make mistakes in your own methodology.

  3. Have you taken a look at Physics By Inquiry? It’s a curriculum designed to train pre-service elementary science teachers and it is pretty fantastic. Two things I notice—PBI takes nearly 40 pages of mostly guided inquiry activities to move from introducing lenses to having students think about applications like microscopes and telescopes. Obviously, you don’t have that sort of time. But there are a number of activities in this section that are designed to help students discover some of the bigger ideas of optics, like focal length on their own. The very first experiment just has students comparing qualitative observations about 2 convex lenses with different diameters, and asks them to just describe their observations, which seems like a lower barrier to entry than asking an question about where real images will be formed by a lens. Though I’m sure you’ve covered these vocabulary points already, the question still seems to call for a “right” answer that the confused student will ask his or her peer “what did you put for number #2?”

    Regardless of whether you use it for labs in your classroom, I’ve gotten tremendous value from working through PBI myself to both get a deeper understanding of the phenomenon, but also see how they structure the labs and activities in a way to break down complex ideas into a series of steps that don’t feel like a cookbook.

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