When black copper oxide powder is added to sulfuric acid, it reacts to form blue copper sulfate solution
If more and more copper oxide is added, eventualy all the sulfuric acid will react. After this point any copper oxide added will be in excess and clearly visible as a black powder in the new blue solution.
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Use this student worksheet to think about excess reactants in the context of the reaction between copper oxide and sulfuric acid.
View and download more Johnstone's triangle worksheets
Learning objectives
- Explain the changes observed when copper oxide is added (in excess) to sulfuric acid.
- Recognie the compounds represented in the equation.
- Calculate the expected mass of excess copper oxide.
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
Share the structure of the triangle with learners prior to use. Tell them why you are using it and how it will help them to develop their understanding. Use an ‘I try, we try, you try’ approach when introducing Johnstone’s triangle for the first time.
More resources
To further develop learner’s thinking in all areas of Johnstone’s triangle, try our Developing understanding of limiting and excess reactants (quantitative) worksheet or to introduce learners to the fundamental idea of limiting and excess reactants, try our Developing understanding of limiting and excess reactants (qualitative) worksheet. These include icons in the margin referring to the conceptual level of thinking needed to answer the questions.
Downloads
Excess copper oxide Johnstone's triangle student worksheet
Editable handout | PDF, Size 0.21 mbExcess copper oxide Johnstone's triangle teacher notes
Handout | PDF, Size 0.24 mbExcess copper oxide Johnstone's triangle student worksheet
Editable handout | Word, Size 0.53 mbExcess copper oxide Johnstone's triangle teacher notes
Editable handout | Word, Size 0.52 mb
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