Chemistry Solutions

Many teachers would admit that grading papers is the least favorite part of their job. Why, then, would any teacher willingly sign up to spend seven straight days grading exams from 8 a.m. until 5 p.m.? Honestly, the reason that I first decided to apply to be an AP Exam Reader was that it was an eligibility requirement for becoming an AP Consultant and providing workshops for new AP Chemistry teachers. As is typical, it was a few years after applying that I eventually received an invitation.

In June 2014, I entered my first Reading experience with a fair amount of dread. On Day 1 of the Reading, we were assigned groups for training on the use of the rubric. I learned that a lot of research and statistics goes into this process, and it really does ensure that every individual teacher can fairly and consistently use the rubric to assign scores. There is even a hierarchy of scoring checks to ensure that this is true.

What struck me that day was the pure professionalism of everyone involved. There were clear and strict beginning and ending times, and everyone followed the rules. As a new Reader, I appreciated that others would gently guide and correct me if I inadvertently went outside the rules of professional behavior — such as talking specifics about any student’s answer. There is an unwritten but well-followed rule about respecting the efforts of the students. We do not speak condescendingly about student responses, but we do note common errors, misconceptions, and misinterpretations we find in the student work. These notations are what eventually end up in the Chief Reader’s webinars that help teachers know what kinds of things they might want to pay closer attention to during the next year’s lessons. What most impressed me by the end of Day 1 was the professionalism of this group of people, and the amount of respect that the group affords to our students during this process.

Hitting our stride

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By Day 2, full-time scoring was underway. At this point, there was a lot more monotony than there was during the scoring training sessions. What interested me, however, were the insights I started to get after scoring about a day’s worth of papers. Each group of Readers is trained on scoring only one of the seven free-response questions. This means that for seven straight days, my brain was focused on a single set of ideas. During the day I was noting how students responded to these questions, and during the off-periods I was thinking about my own practices and wondering how they stacked up.

I quickly learned that keeping a notebook next to me while grading was necessary because my brain would wander to strategies that I could use to try to prevent this or that misconception. Writing it down allowed me to save it for later so I could continue scoring with focus! Of course, I was careful not to record details from any student response. As professionalism dictates, I only wrote down the generalities I noticed over a wide range of exams, along with brief thoughts on potential strategies to counteract these incorrect ideas.

Days 3-7 were similar to Day 2. I was surprised that, after the sheer number of exams that I had scored, even on these later days there were new forms of misconceptions arising in the students’ responses. I added to my notebook almost every day. A valuable part of my entire Reading experience was listening to and participating in the discussions among both high school and college instructors throughout the week that revealed the varying instructional approaches to each topic. These discussions began during scoring training and continued throughout the week during breaks and meals with people who were scoring different questions. By the end of the Reading, I had so many new ideas that it felt like I had just finished a professional development training. That year, I returned home with pages full of ideas that I wanted to try in the following year. These were inspired both by my notes while scoring and by conversations with my Reading colleagues.

After this first, satisfying week, I decided I would keep coming back each year for this crazy event. Each year since then, I have experienced the same kind of satisfaction from understanding student misconceptions and being inspired with new ideas. It is pretty unlikely that a Reader will score the same topic from year to year, so I came home each year with a new focus on what to do better.

Taking on a new role

During this past June, I was invited to be a Table Leader (TL) for Question 2 of the AP Chemistry Exam. This promotion was a result of feedback from my own leaders each year. If a Reader garners enough good feedback, they go on a list that is accessed when TLs are needed. Being a TL was a different experience, because I was invited into the pre-scoring process where the Question Leaders (QL) create guidelines to ensure that all of the Readers assign scores consistently with the rubric. This was a beneficial experience, because it showed me how important it is to teach clarity to my students. There are many cases where I had a gut feeling that a student probably knew the answer, but what they wrote was incorrect, so they lost the point. Though in past practice, I have guided my students toward succinct answers, rather than long, drawn-out paragraphs, I now add a statement about the importance of choosing your words carefully. I am not a person who believes in teaching to a test, but having experience with this test has definitely opened my eyes to skills that the students need help with.

Being a TL, I was now a part of the hierarchy of scoring checks. Most of the first day I would only score exams that the Readers at my table had already scored. This is called “back-reading.” The practice is that if the TL and Reader get different scores on a particular student’s answer, they discuss it and come to a consensus on the score. This allows the TLs to report back to the QLs if any new issues need to be addressed with the whole group. The QLs also “back-read” the TLs to further ensure consistency. Once the Readers show appropriate consistency, the TLs are free to start scoring their own exams, thus adding to the volume of exams scored.

During both the back-reading and the regular scoring, I kept my idea notebook by my side. The responses that struck me the most this year were from parts a-c of Question 2. After reading a large variety of incorrect responses, I noticed a theme that I probably wouldn’t have noticed after grading only the relatively few responses from my single AP class. The context of the issue was in interpreting equilibrium mixtures, but I believe the deeper misconception was in interpreting particle models. The students had a difficult time understanding that the reactants and products can occupy the same beaker. Additionally, it was clear that they struggled with the concept of reactants becoming products in a stoichiometric way. I began to think about how I model reactions with my classes and wondered if there was a better way that might give students a deeper understanding of this type of process.

Rethinking old teaching habits

Like most chemistry teachers I know, when discussing equilibrium reactions, I talk about the left and right sides of the equation and say things like, “molecules are added to the right side, so it will shift to the left.” I usually try to clarify to students that it is all happening in one beaker, but the language used when discussing these phenomena may add to the misconceptions the students have. Though I can’t get into specifics, many of the responses I scored on the AP Exam referred to the “sides” of the equation as though they were separate entities, rather than components of a single system.

I have used particle representations for as long as I can remember, but I now realize that the way I use them may be contributing to the misconception that I just recognized. When drawing particle models, I typically have students draw either a “before-and-after” picture or write a balanced chemical equation as particles. In my first-year classes, students use model kits to create a set of reactants (I tell them how many of each), then break them up to turn them into products to show them how the law of conservation of mass works with a chemical equation.

I wondered if I could change my strategies a bit to more distinctly model how the reactants and products are related. What if I had the students physically manipulate a model of the reaction within the same vessel, rather than as a before-and-after scenario? I believe this could help them to see a chemical reaction more as a rearrangement of atoms than as separate sets of reactants and products. This small change could help students make better sense of the stoichiometric idea that reactants turn into products in set proportions, forming a mixture of reactants and products until one or more species is entirely used up, or until an equilibrium mixture has been reached.

A change in approach

To address the misconception I had observed in students’ answers, I created a lesson that specifically attempts to show students how a set of atoms can be arranged to look like reactants or products, and that the number of atoms they start with limits how many reactants and/or products are possible. The lesson is created for an equilibrium unit, but the idea could be extended to any stoichiometry lesson. It is written to use a typical modeling procedure, but in the hands-on portion, everything happens within a single beaker. Students are asked to draw pictures to represent the physical models they created to purposefully connect before-and-after pictures to a single system in various phases of reaction.

Questions are included to direct student attention to how our chemistry language about a model is not necessarily indicative of what happens in the system being modeled, and also to ask them to suggest better ways to talk about it. A teacher could also extend this lesson by having students create a series of stop-action photos of their beaker system each time they make a change.

Figure 1. Manipulatives are used in the student activity to model the behavior of particles in the system.

I plan to adjust my language regarding reactions this year. I will try to limit my use of “right” and “left” and replace it with “reactants” and “products” (see examples in Figure 2). Additionally, I will put more focus on the different uses of the various models (see Figure 3). With both of these strategies and the associated lesson, I believe I can reduce the misconceptions generated in my students while teaching topics involving chemical reactions.

Figure 2. Changing our words to reduce misconceptions

Figure 3. Clarifying the uses of models

As you can see, becoming an AP reader has been a valuable experience for me. The only negative is that living in the northeast, where our school years go well into June, I have to miss a week of school at the end of the year. This is not ideal, but the experience has been worth it. I now understand why teachers and college instructors willingly submit themselves to this experience. I can also now defend how this experience is truly a professional development experience.

There are a variety of ways that I believe this single-beaker idea could be used in both first-year and AP chemistry classes. I plan to try it out this year, and hope that you will, too!

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