How to teach conservation of mass

You can’t create or destroy matter. A sandwich will have the same mass as its ingredients and a smashed wine glass will weigh no more or no less than before it was dropped. But beyond the obvious sit a number of interesting observations that make the seemingly intuitive law of conservation of mass not so intuitive after all, such as when sugar dissolves in water – it disappears but mass is conserved. Not all students are confident with the idea that mass is conserved when a substance is dissolved or heated. Use this article and accompanying classroom activity to help students visualise the components of a reaction with the examples of dissolving sugar and heating copper(II) carbonate.