Building a Model: Part 1

Happy summer to all you teachers out there!

While I am very excited to have regained my bathroom freedom, I am even more excited about the PD I have planned for this summer. This summer is all about the modeling!

I am currently at  an advanced modeling workshop for the next 3 weeks and I thought this would be a good place to synthesize what I have been learning. The purpose of the advanced workshop is to construct a modeling unit from the ground up. The first week (and the topic of this post) consists mostly of defining your model, building your ladder of knowledge and filling in possible activities.

Step 1: Choose a Topic

This sounds deceptively easy. My group started with the topic “modern atomic theory.” Seems doable right? We soon found out that this topic was leading us straight into other topics like nuclear reactions, electronic structure and periodic trends. We concluded we either needed to take the nuclear route or the electronic route. Nuclear route won because we felt like we had less materials to address this topic.

Step 2: Define the Model

Once we had a topic, we needed to define our model. The model is the framework that all the content in the unit will be built on. A unit can contain more than 1 model. Our nuclear chemistry unit has 2 model statements:

  • The atom is divisible into smaller subatomic particles, which determine the identity of the atom and have different electrostatic charges and masses.
  • Atoms of one element can change into atoms of another element through radioactive decay.

These model statements are the guide for our entire unit. Our students must be able to complete the objectives of the unit using the above models.

Step 3: Build the Ladder

The next step was to build a ladder of content we want the students to know throughout the unit. The hardest part about this step was thinking only about content, not activities. As teachers, we are always thinking, “what activity do I have for this topic?” With a topic as broad as nuclear chemistry, it would be really easy to put together a bunch of fun activities that only dance around the content we were aiming for. The ladder helped us pinpoint exactly what we wanted our students to get from the unit and then we could fill in the “how.”

For nuclear chemistry, we wanted to build off the AMTA Modeling materials. Our students already knew about the Democritus, Dalton and Thomson models. Our nuclear unit needed to start with Rutherford. We decided to continue in the tradition of the Modeling curriculum and structure our unit historically. Our ladder looked something like this:

  1. Rutherford (nucleus is a dense positive charge in the center of the atom)
  2. Mosely (atomic number is what defines an element, not atomic mass)
  3. Chadwick (the nucleus is composed of positively charged protons AND neutral neutrons)
  4. Fermi (unstable nuclei can decay at a predictable rate, releasing a large amount of energy that can be harnessed to produce electricity)

Step 4: Fill in the Activities

Our last task of the week was to start filling in the activities. Again, another task that sounds deceptively easy. This task was especially difficult because we chose a very abstract model. Students cannot physically see the nucleus of an atom, so how do we convince them it is there? Between analogous activities and pHet simulations, we were able to make the abstract idea of the nucleus more concrete.

The trouble we ran into along the way was we were so concerned about making everything concrete, that we were losing some of the content in our analogies. At some point, every analogy fails. In the end we had to remember that our audience is intro level chemistry students who do not need every single idea spoon fed to them. We kept the strong analogous activities, like our Plinko style board to show the Rutherford model of the atom, and threw out our weaker analogies, like our weighted blocks to show the extra mass the neutron adds to the nucleus.

By the end of the week we had a pretty solid unit and were able to assign tasks to every group member. Building a model from the ground up is incredibly work intensive but it really forces you to understand the framework of Modeling Instruction.

If you haven’t been to a Modeling workshop, add it to your to-do list. Check out for dates and locations. Happy curriculum writing!


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