Developing understanding of carbon allotropes

This worksheet is part of the Johnstone’s triangle series of resources, designed to help learners to move between different conceptual levels of thinking in key chemistry topics. 

Learning objectives

1. Recall the structure of different allotropes of carbon.
2. Explain why carbon can form different giant structures.
3. Explain why diamond does not conduct electricity but graphite does.

How to use this resource

This resource aims to develop learners’ understanding of the structure of carbon allotropes. The questions encourage learners to think about how the structures are represented and what this means at the sub-microscopic level. 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 Carbon allotropes Johnstone’s triangle worksheet which guides learners to think about the similarities and differences between graphite and diamond at a macroscopic, sub-microscopic and symbolic level.

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 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 circulate examples of substances in the classroom, run a class practical of a chemical reaction or show a teacher demonstration of properties.

Give learners physical models to use and manipulate, such as a Molymod™ kits or counters.

Additional support may be needed for any learners still lacking in confidence in the required symbolic representation, for example by sharing and explaining a diagram or a simulation that can show movement of the particles.

Answers and guidance

Download the teacher notes to find the answers to the student worksheet.

There are three multi-part questions in the student worksheet. The first question supports learners to recognise, interpret and evaluate typical diagrams representing the sub-microscopic structure of different allotropes of carbon. Question two guides learners to use dot-and-cross diagrams to explain why carbon can form giant structures. The final question challenges learners’ thinking about a diagram of the structure of diamond by making links to atomic structure. Learners are then asked to use this thinking to explain macroscopic properties of diamond and graphite.