Teach Secondary Issue 14.3

Get the balance right Daniel Harvey looks at the processes involved in teaching students how to balance chemical equations... I nmy youth, I loved the zany antics of Morecambe andWise – particularly the duo’s classic sketches with famous guests, such as André Previn, Elton John and Bruce Forsyth. Now, think of all the chemistry topics science teachers love to teach. The list may well include practical experiments that involve making salts, testing the reactivity of metals or demonstrating displacement. Or investigating how the speed of chemical reactions can be changed, or the reactivity of group 1 metals. It’s unlikely that the teaching of chemical equations will be near the top of that list, or even on it at all – yet the importance of this topic for mastering chemistry at GCSE and A Level can’t be understated. It’s the ErnieWise of the post-GCSE chemistry curriculum– the ‘straight topic’ that enables more interesting areas to flourish and grab students’ attention. This article has an accompanying resource (see tiny.cc/BCE ) that breaks the teaching of this concept down into six discrete stages. The resource isn’t meant to be exhaustive, but rather added to by teachers who know their students well, and will understand when to ABOUT THE AUTHOR Daniel Harvey is a GCSE and A Level science teacher and lead on behaviour, pastoral and school culture at an inner city academy extend a particular stage, or increase the amount of challenge in practice questions. 6 stages The following six stages shouldn’t be mapped to six different lessons, but instead seen as progression points. They describe what students should know, in sequence, so that they can consistently write correct balanced symbol equations. The resource starts with a knowledge organiser, so that students can learn the shared science vocabulary they’ll be using in later years, and the processes they will be expected to use in their work. Stage 1 is all about setting the scene using powerful demonstrations, such as hydrogen balloons and thermite reactions to grab students’ attention and apply these to the theory. This initial stage should refer to the knowledge organiser, key terms and principles of equations. It will be mainly teacher-led, and can include the use of more examples so that students can fully grasp these basics. Stage 2 emphasises how balanced chemical or symbol equations need to be preceded by word equations. At this stage, we want to focus on getting students to write word equations from reaction descriptions. Teachers can then assess howmuch practice students need from five questions presented within the resource. Stage 3 sees students use the periodic table to decode and describe chemical formulae. (assuming this hasn’t already been covered). Teachers must assess howwell their group can apply this learning, and then extend the amount of practice if needed. The resource includes an example with brackets, intended to make teachers think about when these formulas will be introduced to student learning and practice. It also extends the idea into putting numbers before formulae. Stage 4 involves learning how to identify what a balanced symbol equation is, and developing the ability to justify decisions. Stage 5/6 is one stage split into two, so that students can first practise matching chemical formulae to substance names and when to use the appropriate symbols. Some groups might not need this, while others might need to take their time over it. Identifying if an equation is balanced, and knowing how to correctly balance it if not, then becomes the focus of the final stage. Teachers should listen to howwell students solve the problems presented to them, and then decide if and how best to extend the challenge. Acritical topic It’s important to bear in mind the ways in which your teaching of equations will link to students’ future studies. This is a topic that’s critical for the chemical calculation tasks students are assessed on in GCSE combined science – and indeed one that’s essential for any tasks that will involve applying molar calculations. “The importance of this topic can’t be understated” 73 teachwire.net/secondary S C I E N C E