Conservation of mass in dissolving and precipitation | 11-14 years

A photograph of three test tubes in a test tube rack, each containing a different colour of precipitate including copper hydroxide, iron(III) hydroxide and iron(II) hydroxide

Source: © Shutterstock

Explore what happens during precipitation reactions and when substances dissolve using this lesson plan with downloadable activities for 11–14 year olds.

This simple practical activity challenges students’ thinking about mass conservation when substances dissolve or when chemical reactions produce precipitates. Working in small groups they carry out a simple experiment and agree answers to questions, with the aim of being able to explain that:

Mass is conserved during dissolving.
Mass is conserved during a precipitation reaction.
Whatever change occurs, the total mass of the substances involved does not change.

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