Use Johnstone’s triangle to introduce calculations of reacting masses
Learners consider the difference in appearance between tin and tin oxide. They show that they understand how to represent the extraction of tin from the compound symbolically, before tackling calculations involving mass, relative formula mass and moles.
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Use this student worksheet to introduce calculations of reacting masses and link them to learners’ observations and understanding at three different conceptual levels.
View and download more Johnstone's triangle worksheets
Learning objectives
- Name reactants and products from their description.
- Calculate relative formula mass from a given formula and relative atomic masses.
- Calculate the mass of a product from the mass of a reactant.
How to use Johnstone’s triangle
Use Johnstone’s triangle to develop learners’ thinking about scientific concepts at three different conceptual levels:
- Macroscopic: what we can see. Think about the properties that we can observe, measure and record.
- Sub-microscopic: smaller than we can see. Think about the particle or atomic level.
- Symbolic: representations. Think about how we represent chemical ideas including symbols and diagrams.
For learners to gain a deeper awareness of a topic, they need to understand it at all three levels.
When introducing a topic, do not try to introduce all of the levels of thinking at once. This will overload working memory. Instead complete the triangle over a series of lessons, beginning with the macroscopic level and introducing other levels, in turn, once secure.
All of the levels are interrelated, for example, learners need visual representation of the sub-microscopic in order to develop mental models of the particle or atomic level.
Further reading
Read more about how to use Johnstone’s triangle in your teaching with these articles:
- Develop deeper understanding with models
- Improve students’ understanding with Johnstone’s triangle
- Practical ideas for using Johnstone’s triangle
Norman Reid’s book The Johnstone triangle: the key to understanding chemistry provides a more in-depth overview, the first chapter is available to read online.
Scaffolding
It is important to share the structure of the triangle with learners prior to use. Tell them why you want them to use the triangle and how it will help them to develop their understanding. Use an ‘I try, we try, you try’ approach when you are introducing Johnstone’s triangle for the first time.
Next steps
To further develop learners’ thinking in all areas of Johnstone’s triangle, try our Developing understanding of reacting ratios (masses) worksheet. This includes icons in the margin referring to the conceptual level of thinking needed to answer the questions.
Downloads
Tin from tin oxide Johnstone's triangle student sheet
Handout | PDF, Size 0.35 mbTin from tin oxide Johnstone's triangle teacher notes and answers
Handout | PDF, Size 0.38 mbTin from tin oxide Johnstone's triangle student sheet
Editable handout | Word, Size 0.58 mbTin from tin oxide Johnstone's triangle teacher notes and answers
Editable handout | Word, Size 0.58 mb
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