I’m just starting my second week of a chemistry modeling workshop. While I’ve been furiously taking notes, it’s taken awhile to transfer it to my blog. So over the remainder of the workshop, I’ll post about my experience, and give you an idea of what the modeling workshop is like. If you find this interesting, I strongly encourage you to sign up for a modeling workshop. It’s a large time investment, but some things you can only really observe and experience in context.
After introductions, we took an ABCC (Assessment of Basic Chemistry Concepts), which is similar to the Force Concepts Inventory used for modeling physics and the Chemical Concepts Inventory published in the Journal of Chemistry Education. Students are typically given this pre-test on the first day or two, and will retake it after at the end of the year. We will retake it on the last day of the workshop.
Next, we viewed a powerpoint on what modeling instruction is, and why it is effective. Most of you reading this blog tend to agree that the transmission model of education isn’t particularly effective or desirable when it comes to student understanding. Modeling asks students to construct and use scientific models (diagrammatic, graphical, algebraic) to describe, explain, and predict phenomena. Models are evaluated not against a textbook/reference standard, but by a comparison with empirical data, ideally collected by students. I’ve embedded the presentation here:
Eureka/Ring of Truth
The modeling curriculum encourages the use of certain videos to introduce topics, or help students move ideas along in their minds. One particular series, Eureka, is used to introduce the first lab on mass. I managed to find this video on YouTube:
The videos have a bit too much anthropomorphizing for my taste, but it does help to explain somewhat abstract ideas in a relatively short chunk of time. The other series used frequently in the curriculum is Ring of Truth by Professor Philip Morrison. The particular clip we observe here is on conservation of mass, and shows the effect of a quite elaborate series of physical and chemical processes on the mass of a closed container. Its fun to watch!
Mass & Change Lab
The Mass & Change Lab is a relatively simple activity for students to observe and describe the relationship between the mass of a substance before and after it undergoes some type of visible change. In the first investigation students determine the mass of a piece of steel wool, and then stretch it out, and determine the mass of the new, expanded steel wool. Students can predict whether they expect the mass to increase, decrease, or stay the same, and then test it. Most students will predict that the mass will stay the same, but for nearly all the mass will decrease. (due to small pieces falling off when you stretch the steel wool). In the follow-up discussion, you can have a discussion about lab technique and observations, and ask how they might modify the procedure to ensure that the breaking steel wool will be massed as well.
Next, you discuss the next 5 investigations with students, and devise a procedure to test each. The investigations are
2) Melting ice
3) Burning steel wool
4) Dissolving sugar in water
5) Formation of a solid when two clear liquids are mixed
6) Dissolving Alka-Seltzer in water
Students also make predictions about what will happen beforehand (clickers/polleverywhere?), then perform the tests.
After the lab is complete, students split into 6 groups and on large whiteboards draw a diagram to describe what happens for one process on the smallest level. During the “Board Meeting,” students tease out a particulate-description of matter, and relate their particle models to the observed mass change. The emphasis of the discussion is how the diagram demonstrates a mass change, and what happens when mass change does occur. Specific terminology (precipitate, combustion, carbon dioxide) can be avoided here, as the main purpose of the activity is to conceptualize the idea of mass conservation.
After this discussion, students complete WS 1, which revisits the lab investigations, and checks for understanding of the underlying concept.
I really like this activity. It is very simple, and uses very common materials that most students have some experience with. It is also important for students to make the leap early on from a continuous view of matter to a particulate view.
After defining mass as “stuff,” we begin to look at volume as an amount of space. In this lab, we compare the calculated volume of water in a vessel of some simple geometric shape to the measured volume in a graduated cylinder. Students look at 5 different volumes, and plot the measured volume vs. The calculated volume.
I love this activity because
- it’s very easy (though teenagers + water tend to make a little mess)
- students tend to take conversions (1 mL = 1 cm3)for granted. Here, we can demonstrate, with real data, why this relationship is true
- when asked to make an equation for a line describing the relationship between measured volume and calculated volume, students actually plug in the variables used in this experiment (not a generic y = .999x + 2, but measured volume = .999 * calculated volume + 2)
- you can have a real discussion about the meaning of the y-intercept (what does it physically mean? Does it make sense in this case? When is it okay to disregard it?)
- you can discuss what slope means. Not a generic calculation of slope (rise over run) but a verbal description of the relationship between the variables being studied.
- you can discuss uncertainty in measurement (why isn’t the slope = 1? Why aren’t all groups slopes the same? Are they close enough to 1 to say that it should be 1?)
While the lab is technically simplistic, these discussions will be very useful when applied to more complex concepts (density –> gas laws –> ??)
For homework, we read an article by Bruce Alberts (Restoring Science to Science Education)