Developing understanding of interpreting chemical equations for ionic compounds

Developing understanding is a series of resources that encourage learners to connect their thinking at the macroscopic, sub-microscopic and symbolic levels. This resource, which includes teacher notes and a student worksheet, is designed to help learners develop mental models of what is represented by a balanced chemical equation that includes the formula of an ionic compound. 

 Learning objectives

1. Link the formula and state symbol of reactants and products to observations of a chemical reaction.
2. Interpret the meaning of the formula of different ionic compounds.
3. Interpret a chemical equation to identify the structure of each reactant and product and whether each is made up of atoms, molecules or ions.
4. Recognise that a chemical equation can be used to work out the mass of product that could be produced from the given mass of a reactant.

How to use this resource

This resource aims to develop learners’ understanding of how balanced chemical equations show the ratio in which atoms, molecules and ions of different substances react or are produced. The questions encourage learners to think about how the chemical formula and state symbol of elements and compounds connect to their structure and what is observed during a chemical reaction. The final question encourages learners to think about how a balanced chemical equation can be used to determine the mass of substances that react or are produced. As a result, learners should develop more secure mental models to support their thinking about this topic.

• When to use? Use after initial teaching or discussion of this topic to develop ideas further. You can also use as a revision activity.
• Group size? Suitable for independent work either in class or at home. Or use the questions for group or class discussions.
• How long? 15–30 mins.

Johnstone’s triangle

Johnstone’s triangle is a model of the three different conceptual levels in chemistry: macroscopic, symbolic and sub-microscopic. You can use Johnstone’s triangle to build a secure understanding of chemical ideas for your learners.

Introduce learners to Johnstone’s triangle with our Magnesium and oxygen reaction Johnstone’s triangle worksheet, which guides learners to recognise chemical formulas and symbols in equations and describe what is being shown in a balanced chemical equation.

Scaffolding

This worksheet is ramped so that the earlier questions are more accessible. The activity becomes more challenging in the later questions. You can give extra explanations for the more challenging questions. If completing as an in-class activity it is best to pause and check understanding at intervals, as often one question builds on the previous one.

It is useful for learners to observe macroscopic properties first-hand. You could run a class practical of relevant chemical reactions or carry out a teacher demonstration. It is important that learners can observe the detail of the reactions so a camera may be useful.

It may be helpful to learners to show them a physical model or a digital image of a simple ionic lattice such as sodium chloride which can be rotated.

Additional support may be needed for any learners still lacking in confidence in the required symbolic representation. Increasing fluency in recognising symbols and common formulae through quizzing may be beneficial, along with matching to the physical appearance of elements and compounds to improve recognition.