Help students understand how mass is conserved when a substance is dissolved or heated

Photo of apparatus used to heat copper (II) carbonate in a test tube

Source: © Science Photo Library

Students often get confused by the decrease in mass when the green CuCO3 powder is heated to form black copper(II) oxide

Not all students are confident with the idea that mass is conserved when a substance is dissolved or heated. Indeed, a number of interesting observations make the seemingly intuitive law of conservation of mass not so intuitive after all. For example, when sugar dissolves in water it disappears but mass is conserved.

Use this classroom activity to help students visualise the components of a reaction using the examples of dissolving sugar and heating copper(II) carbonate. Download the activity as a starter slide or as a worksheet, together with an answer sheet.

Also, use the thinking questions to challenge students to consider what happens to matter during and after a reaction.

Use this resource alongside the Education in Chemistry article, Conservation of mass.