Teach “naming compounds” with a decision tree

Naming compounds was a frustrating topic

This is a topic that my Chemistry students always struggled with. There are just so many rules! They were becoming frustrated and giving up. So I did what I always do when my kids are having trouble. I reflected on the lesson and thought of ways to make it more accessible. The first thing I did was grab a piece of paper and started sketching out all the rules for naming compounds…then it hit me! A decision tree!

What’s a decision tree?

A decision tree is a birds-eye view of all the rules in one spot. It was what I naturally felt compelled to do to solve my problem, why wouldn’t it work for them? The image below is an example of what I mean. Do you see how you can get to the correct set of rules by answering a series of simple questions? What a great tool! But take it a step further and allow students to create their own decision trees to really deepen their understanding.

Not smooth sailing

Well, the first time I did this with students it didn’t go well. If you’ve been teaching for any length of time, then you know that they want concrete step-by-step instructions for any project. This project simply is not like that. There are many ways that students can create their decision trees, there is not one “right” answer. So I decided that I really needed to teach them about decision trees before they would be confident enough to tackle this project.

Show examples

Students are often familiar with many different kinds of graphic organizers but I quickly realized that decision trees were not among them. They needed to be prepared for creating a decision tree so that they could focus on the naming rules rather than the nuts and bolts of making a decision tree. I begin with a couple of simple examples about everyday things. “What should I eat for breakfast?” and “What do I wear today?” For my Chemistry kids who have already had Biology, I linked it back to dichotomous keys to build on that prior knowledge.

Do one together

Then I lead them through creating a decision tree together on the SMARTboard. I like to use the question “Should you prank your teacher?” I got the idea from an article I read about office pranks (don’t ask).  Not only does this help them learn to create a decision tree but it’s fun and helps you get to know each other better. If you don’t like this idea you can do something like “What should I do after school today?” The picture below shows one that we created together last year.

Give them the rubric

Now that they have a good understanding of decision trees in general, they can use this tool to develop a deeper understanding of naming and writing compounds. I typically give them the rubric that I will use to grade their trees. It includes all of the types of bonds and the formulas and names that I will use as “tests” for their decision trees.  I explain that a good decision tree will correctly lead me to the set of rules I need in order to name or write each formula on the rubric.

Make it big

You know those rolls of colored bulletin board paper that your school has? Well I keep a roll of white in my classroom for these kinds of projects. I like that when they are doing something on large paper, they have to move around, climb onto tables, stretch out on the floor, etc. In my experience, physically getting into the project, helps them be more mentally connected to the project. Take a look at some pictures of the process below.

The data

The first year I did this project, it was after I had already tested on the material. The test average was a whopping 63%. Since naming and writing compounds is necessary for everything else we would be doing for the rest of the semester, I couldn’t move on until they got it. After completing the decision trees and using them to complete some mixed naming practice worksheets, I retested. Class average went up to a much improved 82%. I was much happier with that and students had less anxiety over the topic. After that first year, I always include this project before the test as a review activity to help them prepare for the test.

I have done this with both Chemistry and General Physical Science students using different rubrics because Physical science students do not get into polyatomic ions or acids and bases. They needed a lot more support than Chemistry students did but most managed to created a usable decision tree without much struggle. Try this with your students and I guarantee that they will struggle less with naming and writing compounds.  Let me know how this works out for your students!

 

 

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