Effect of modeling pedagogy on IB Chemistry HL scores

Three years ago was a very busy time in my teaching career.  I had just attended a three week long workshop on teaching chemistry using modeling pedagogy.  I walked away ready to completely overhaul my teaching methods and even institute standards based grading in my chemistry class.  At the same time I was teaching IB chemistry HL for the first time ever. I had a group of seniors in their second year and a group of juniors starting the course.  Today we received our third set of data and the 2018 group is our first group of students to have been taught using modeling pedagogy prior to taking IB Chemistry HL. The first two groups (2016, 2017) took chemistry prior to IB Chemistry HL, but they took chemistry before I had attended the workshop and were taught using traditional teaching methods.  

Figure 1: IB score distributions from 2016-2018

Figure 2:  IB average scores (3.96, 3.74 and 4.42) from 2016-2018

The data is limited because it only represents 25, 27 and 31 students for the three groups.  There is also likely variation in my teaching abilities as I have become more familiar with teaching IB Chemistry HL.  But the data does match my experiences while teaching the three groups. The modeling pedagogy increased the ability of the students to question the material we learned.  As the content became more difficult there was a presence of mind to push for evidence behind the conclusions I would present. While we did continue to use modeling teaching for some lessons (equilibrium, crystal field splitting) the biggest difference to me was the level of analysis that students applied in their learning was at a deeper level.  They made more connections between content areas, they were able to visualize systems at the particle level and change back to symbols quicker, they had more experience and context to learn in a more permanent fashion.  

None of these comments are an indictment on the first two groups.  All three cohorts of students had remarkably intelligent and successful students that did brilliant work in class.  They all had strong metacognition and did deep levels of analysis of chemistry. I also do not feel that I taught these first two groups poorly.  We did a lot of engaging activities and reflection for all three groups. The modeling approach in the chemistry prerequisite course I believe to have elevated the 3rd cohort to an improvement of that learning.  There is a frequent concern amongst teachers that altering teaching methods will lead to students not being prepared for the most challenging coursework that they will take in the future. While there is a lot of uncertainty and unreliability in the data in Figure 1 and Figure 2 based on student and teacher variation, there is evidence to support modeling having a positive impact on top students that move on to take a course such as IB Chemistry HL.  To get the IB Diploma students need to average a 4 score on their classes with a few technicalities mixed in. The % of students achieving a 4 or better improved from 52% to 59% to 68% over the three years. Many students that get a 3 in HL chemistry still get their diploma and students getting a 3 or better went from 80% to 93% to 93%. Our diploma rates for the three years were steady at 79%, 79% and 82%. It will be another two years before I have a group test as our program has grown and I now only teach every other cohort.

Update with 2020 scores:

Do people with lighter skin have different sunscreen needs?

We spent a class period researching in groups and a class period discussing our findings.  The prompt was to construct an argument that skin color matters for sunscreen use and an argument that skin color does not matter.  From there our groups diverged greatly as they built up arguments and pertinent explanations.  

Figure 1:  Whiteboard 1 explores the mechanism by which UV light causes DNA mutations

The wide variety of information in the various whiteboards led to some great discussion on content as well as generic science.  We discussed if knowing the mechanism of DNA damage by UV light is relevant so long as we see the data in Whiteboard 2 (below).  Students split but offered mostly arguments that mechanism knowledge is highly relevant to evaluate the conclusions from the data of skin cancer rates.  Multiple examples were offered such as some races might be located where they experience different exposure to sunlight, different races might also use different amounts of sunscreen on average and reporting of race can be inconsistent.  In general most students felt that just knowing skin cancer rates is insufficient and could be correlation without causation.  

We also talked about the mechanism by which UV light originates and under what conditions an electron can accelerate so much that it produces such high frequency light.  We connected the emission and absorption of light with the Balmer series for hydrogen.  We reviewed the spacing of energy levels and I instructed about the differences in energy level spacings for gaseous atoms/ions compared to molecular excitations.  We connected this later with Whiteboard 6 by talking about how a slight adjustment to a molecule can cause a minor change in the frequencies of light absorbed and how pigments and dye research often utilizes electron rich and electron deficient functional groups to shift color.   

Figure 2:  Whiteboard 2 found cancer rates based on race

Figure 3:  Whiteboard 3 went full “Natural News” to locate some arguments against
sunscreen

This board led to a good discussion on sources of scientific information, how sources manipulate data and experiment into “clickbait” articles.  We posed the question “Are any of these things actually bad or do they just sound bad?”  For example, if sunscreen ingredients are present in breastmilk, is that bad or is it so infrequent and low in concentration that it is irrelevant?  We talked about how the FDA does not have jurisdiction over supplements and how labels for supplements are sometimes shown to be incorrect.  We also compared this board to the risks of not wearing sunscreen using Whiteboard 2 (above).  

Figure 4:  Whiteboard 4 summarized different wavelengths of UV light and nanoparticles
used for sunscreens

Figure 5:  Whiteboard 5 looks at melanin and interactions of sunscreens with UV light

Figure 6:  Whiteboard 6 looks at different chemical structures utilized in sunscreens

Conclusions that students made included that the SPF data they saw suggested that anything over SPF 50 was a marketing scam and was less healthy than using SPF 50 or lower.  We concluded that the mechanisms by which electrons change motion during electronic transitions in molecules are incredibly difficult to visualize and that this uncertainty can be problematic for understanding.  We concluded that everyone exposed to sun should wear sunscreen because melanin mostly protects from sunburn but not from DNA damage.  We saw a variety of organic molecules used to absorb UV light as well as alternatives such as ZnO nanoparticles.  We started our discussion by looking at how 11 cis-retinal converts into 11 trans-retinal when absorbing visible light and this is the mechanism by which our brain becomes aware of light hitting our retinas.  We talked about the breaking of the pi bond before the rotation occurs and later compared this to potential changes in molecular structure when UV light is absorbed by molecules in sunscreen.  

As a teaching lesson I was highly pleased with the variety of topics to discuss and the variety of information students used to make arguments.  Students looked at chemical structures, DNA damage mechanisms, skin cancer data, sunburn data and how UV light itself varies.  We identified what type of light escapes the sun as a subject that requires more research.  We will continue to use this topic throughout our review.  We saw connections to organic chemistry, quantum chemistry, periodic trends and bonding.  It was interesting to the majority of students.  Some students asked what it was like to be sunburned because they had never experienced it before and most students had limited ideas coming into the discussion but left with much better knowledge.