Developing understanding of the properties of elements and compounds

Developing understanding is a series of resources that encourages learners to connect their thinking at the macroscopic, sub-microscopic and symbolic levels.

Learning objectives

1. Recognise that a compound is made up of a combination of atoms of different elements.
2. Recognise when elements combine to form a compound no small pieces of the elements remain (and so an iron compound is not magnetic).
3. Recognise that the colour of a compound is not a mixture of the colours of the elements with the types of atoms that make up the compound.
4. Explain why a compound formed from two elements has different properties to the original elements which reacted.

How to use this resource

This resource aims to develop learners’ understanding of the combination of elements to form compounds. The questions encourage learners to think more deeply about why a compound does not have the same properties as its constituent elements. 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 Bioethanol Johnstone’s triangle worksheet which guides learners to think about the how the properties of the compound ethanol are different to those of the elements carbon, oxygen and hydrogen.

Johnstone’s triangle and this resource

The icons in the margin indicate which level of understanding each question is developing to help prompt learners in their thinking.

• 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.

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. Our approach has been to apply icons to questions based on what the learners should be thinking about.

Questions may be marked with two or all three icons, indicating that learners will be thinking at more than one level. However, individual parts of the question may require learners to think about only one or two specific levels at a time.

Support

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 this worksheet 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 use a teacher demonstration to show a change in properties. You can find a full method and resources for demonstrating the reaction between iron and sulfur in our Nuffield practical collection.