When I was at school, (ok, I know that it was a long time ago), in one of our very first chemistry lessons in the equivalent of year 7, we were taught to balance equations. In subsequent lessons, whenever we were given an example of a chemical reaction or we did an experiment, we were given a word equation and we were expected to turn it into a symbol equation and balance it. By the time we reached year 9, we were all experts.
When I see a new student, I always ask if they can balance equations and the answer is usually no. It’s taught as a lesson, often in year 10, and because of the time constraints on the curriculum, there is a promise to the children that ‘don’t get it’ that the topic will be revisited. This rarely happens.
Balancing equations is fundamental to chemistry. It shows the structure of the molecules and the ratios of the various atoms in the reaction. It enables numbers of atoms to be converted to moles (more about them in a later blog) and leads to more complicated calculations in the ‘quantitative chemistry’ module.
Being able to balance an equation may only be worth one or two marks, but there is frequently more than one equation to balance, and it usually comes at the start of a much longer question. The rest of the marks will depend on the correctly balanced equation, although I accept that there is always ‘ECF – error carried forward’ to be taken into consideration so all is not lost.
I teach balancing equations initially by the ‘list’ method. List the atoms in the equation and count them. Add more of the one that there is less of. Count again. It sounds straightforward enough but to child that has sat for an hour in complete confusion at school, this can be too much to process. My secret weapon is the box of Duplo bricks. We use different coloured bricks to represent different types of atoms. We put the bricks together to make molecules. The equations appear visual and colourful before the student’s eyes. With a bit of patience and confidence, the students are soon balancing equations with the bricks like a pro. But then comes the tricky bit as I have to take the bricks away. Bricks aren’t allowed in the exam. Now, with a child having the confidence that they can balance an equation, they switch to the list method with ease. My work is done.