Elements, compounds and mixtures | Developing understanding | 11–14 years | Resource

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Encourage your learners to think more deeply about particle diagram representations 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

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A ramped worksheet to help learners develop their mental models of elements, compounds and mixtures. With icons to indicate the conceptual level/s of each question.

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Learning objectives

Interpret particle diagrams of an element in the gas and solid states.
Distinguish particle diagrams of elements and compounds in the gas and solid states.
Interpret particle diagrams of elements, compounds and mixtures of elements or compounds.

How to use this resource

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

This resource aims to develop learners’ understanding of particle diagram representations of elements and compounds. The questions encourage learners to think carefully about the actual diagrams and what the different colour and arrangement of the circles signify. As a result, learners should develop more secure mental models to support their thinking about this topic.

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 Gases in the air Johnstone’s triangle worksheet which guides learners to think about particle diagrams for the mixture of gaseous elements and compounds in the atmosphere.

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.

Answers and guidance

There are three multi-part questions in the student worksheet. The answers can be found in the teacher notes.

The first question develops learners’ understanding of the representation (symbolic understanding) of the arrangement of atoms and molecules (sub-microscopic understanding) in substances that are in the solid or gas state (macroscopic understanding). This question aims to extend understanding from the basic particle model representation, where all particles are represented by a single circle, to the representation of individual atoms and molecules. It is impossible to draw all the particle in a sample of a substance. A particle model diagram represents a tiny section of the arrangement of particles (atoms or molecules) across the whole substance. Therefore, diagrams X and Y do not represent the number of atoms shown, they represent more than a million atoms of each element.

The second question develops learners’ understanding of how colour and the arrangement of circles are used in particle diagrams (symbolic understanding) to represent atoms in elements and compounds (sub-microscopic understanding).

The third question develops learners’ understanding of how to use the colour and arrangement of circles in a particle diagram (sub-microscopic understanding) to identify the number of elements and compounds represented as well as if the diagram shows a mixture. By giving an explanation students are required to explicitly connect the diagram to the types of atoms and molecules (sub-microscopic understanding) being represented and how this justifies the number of elements or compounds identified.