This is the year for trying things in a new order. Some of them have worked to remove some common errors. I always used to teach conservation of mass and equation balancing before completing reactions. I would simply feed the products to them and they would count atoms and balance. But this year I taught them to predict and complete reactions first. It has improved the flow of the class. Here are the reasons why I teach reaction types and predicting products before balancing.
Stability drives reactions
I teach at a Christian school. We have an answer in chemistry that we call the “Jesus Answer.” It’s the answer that always seems to be right. If the chemistry teacher asks why something happens, it is probably “to become more stable”. Why do bonds form? To become more stable. Why do electrons repel? To become more stable. Why do electrons spread out into p orbitals? To become more stable. They have it melted into their brains.
By teaching predicting products first, I can continue that storyline. They will write stable ionic compounds in the products. They balance charges. They look for solid compounds in double displacement reactions. They are actively looking for stability.
Students stop trying to write compounds using coefficients for stability
One common error that I see is that students get confused on the purpose of the subscripts and the purpose of the coefficient. They try to squeeze coefficients in the middle of compounds because they see that they need more of a certain atom. They bring subscripts over from the reactants because they don’t want to “make or destroy” an atom. While I appreciate the sentiment, it is a strange habit to break. You and I find it so easy that we don’t even think about it. But especially in the lower students, we are just up there pulling numbers out of our rears.
If they have been working all year trying to move toward stability, then let them do that first. We will make sure all the atoms are accounted for soon. I have seen less weird answers this year by switching the order.
Counting atoms is easier than making stable compounds
Generally, students find counting atoms on the left side and the right side of the equation easier than writing the correct formula for aluminum carbonate. I prefer to let them focus on the challenge of writing the correct ionic compounds before they have to finish with balancing the equation. When I taught balancing first, students would start balancing with coefficients before they even finished predicting the products. They were so concerned about losing atoms.
Now, they write the stable compounds. Then they go back and make sure that the Law of Conservation of Mass is still being followed. I know that this is the way that it is supposed to be done, but by teaching it in that order, they have made strides in doing it well.
I hope that you have been doing it in this order all along. But for those of you like me, take a look at the order that you teach the skills and analyze it. I think that you will find teaching the order as predict, complete, and balance will strengthen your kids.
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