Developing understanding of states of matter

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. Use the particle model to explain key properties of a substance in the solid, liquid or gas state. 
2. Select a representation of the particle model that best explains a given property. 
3. Explain why a substance in the gas state may be compressed. 

This resource aims to develop learners’ understanding of states of matter. The questions encourage learners to think about the properties of the different states of matter and how these can be explained using the particle model. 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 States of matter: Johnstone’s triangle worksheet which guides learners to think about the properties and variety of everyday uses of copper 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 counters or marbles.  

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

There are three multi-part questions in the student worksheet. Download the teacher notes to find the answers (PDF | MS Word).

The first question develops learners’ understanding of the physical properties of substances in the three states of matter (macroscopic understanding) as well as the arrangement and movement of particles in each state (sub-microscopic understanding) according to the particle model. 

The second question develops learners’ understanding of how different physical, diagrammatic or animated versions of the particle model (symbolic understanding) can be used to explain changes of state in terms of particles (sub-microscopic understanding) and the properties of different states of matter (macroscopic understanding.

The final question develops learners’ understanding of why a gas can be compressed but not a liquid (macroscopic understanding) in terms of the arrangement of particles in each state (sub-microscopic understanding). This also involves developing understanding that the gap between circles in a particle diagram represents empty space (symbolic understanding).