Using models

With the introduction of Working Scientifically into the national curriculum in England comes a greater emphasis on using models in science teaching and an opportunity for teachers to think through some of the difficulties students encounter in chemistry. It is well known that students find it very difficult to make connections between what they observe in the world around them (macroscopic properties) and the sub-microscopic world of particles, atoms and subatomic units. Yet in order to make sense of the macroscopic properties, chemists switch to the sub-microscopic scale where they use explanatory models to try and explain their observations (fig 1). The model used must relate both to the microscopic and macroscopic behaviour of matter observed, and as new data becomes available chemists evaluate the models they are using and if necessary go on to refine them by making modifications.

Using models in the classroom to explain ideas comes with its own set of challenges as the model needs to explain the behaviours as understood by students at a particular stage in their learning. As students’ experience of macroscopic phenomena expands, the model needs to become more complex as well. For example, the model of an atom as understood by pre-16 students will explain most of the phenomena met at this stage but a more complex model is needed later. That does not invalidate the usefulness of the simple model at that stage, but students need to be aware of the progression so they do not dismiss early ideas as incorrect but see them as part of a development, just as our historical understanding of the atom has developed.

The history of the atom is a great example to use with students in class to show how scientific models develop over time, but students often see it as a series of discrete individual models, rather than appreciate the subtleties of how a single model has developed over time as technological advances gave access to further data. 

Dorothy Warren discusses some of the difficulties with teaching scientific models in school science and various methods of teaching with models.