MODELS AND MODELLING IN SCIENCE AND IN EDUCATION
Models are essential to the production, dissemination, and acceptance, of scientific knowledge (Giere, 1988; Gilbert, 1991; Tomasi, 1988). Although their epistemological status is open to debate, they function as a bridge between scientific theory and the world-as-experienced (‘reality’). They can
be simplified depictions of a reality-as-observed, produced for specific purposes, to which the abstractions of theory are then applied. They can also be idealisations of a possible reality, based on the abstractions of theory, produced so that comparisons with reality-as-observed can be made. They can be used to: make abstract entities visible (Francoeur, 1997); provide descriptions and/or simplifications of complex phenomena (Rouse & Morris, 1986); be the basis for both scientific explanations of and predictions about phenomena (Gilbert, Boulter & Rutherford, 1998). Both the design of and interpretation of experimental practices in modern science are often based on the use of computational modelling,
Many models are of material objects and can be viewed as having an independent existence (e.g., a drawing of a reaction flask) or as being part of a system (e.g., a drawing of a reaction flask in an equipment train). A model can be smaller than the object that it represents (e.g., of an aeroplane) or larger than it (e.g., of virus). Some models are representations of abstractions, entities created so that they can be treated as objects (e.g., flows of energy as lines). Inevitably, a model can include representations both of abstractions and of the material objects on which they act at the
same time (e.g., of energy flows in the Krebs’ cycle). A model can be of a system, a series of entities in a fixed relation to each other (e.g., of carbon atoms in a crystal of diamond, of the organs of the human body, of an electric motor). It can be of an event, a time-limited segment of behaviour
of a system (e.g., of the migration of an ion across a semi-permeable membrane, of human gestation and birth). It can be of a process, in which one or more elements of a system are permanently changed (e.g., of a catalytic converter in operation).
The central role of models in the development of knowledge was recognised by the mid-twentieth century (Bailer-Jones, 1999). For example, they have become ‘the dominant way of thinking’ in chemistry (Luisi & Thomas, 1990), something that chemists do ‘without having to analyse or even be aware of the mechanism of the process’ (Suckling, Suckling & Suckling, 1980). It therefore seems appropriate that models play equally important roles in science education. Students should come to understand the nature and significance of the models that played key roles in the development of particular themes in the sciences. They should also develop the capacity to produce, test, and evaluate models of those phenomena that are of interest to science. To do so is to participate in the creative aspect of science and to experience its cultural value.
The roles of models in science education are not easy to discharge, for models can attain a wide diversity of ontological status. A mental model is a private and personal representation formed by an individual either alone or in a group. All students of chemistry must have a mental model, of
some kind, of an ‘atom,’ all those of biology of a ‘virus,’ all those of physics of a ‘current of electricity.’ By its very nature, a mental model is inaccessible to others. However, a version of that model can be placed in the public domain and can therefore be called an expressed model. Any
social group, for example, a school class, can agree on an (apparently!) common expressed model that therefore becomes a consensus model. A social group is of scientists working with a consensus model at the cuttingedge of their science can be said to be using a scientific model, e.g., of a
Schrödinger model of an atom, of a p-n junction in a semi-conductor, of the AIDS virus. A superseded scientific model can be called a historical model, e.g., the Bohr model of the atom, the Ohm’s law model of electrical conductance, the creationist model in biology. On major aspect of ‘learning science’ (Hodson, 1992) is the formation of mental and expressed models by individual students that are as close to scientific or historical models as is possible. Simplified versions of scientific or historical models may be produced as curricular models to aid learning (for example, the dot-and-cross version of the Lewis–Kossel model of the atom). Specially developed teaching models are created to support the learning of curricular models (e.g., the analogy ‘the atom as the solar planetary system’) (Gilbert, Boulter & Elmer, 2000). Sometimes teachers employ curricular models
which can be called hybrid models because they merge the characteristics of several historical models, this having first been recorded in respect of chemical kinetics (Justi & Gilbert, 1999). Whilst of immediate appeal to teachers, for they enable many ideas to be taught at the same time, they
do violence to the history of science for they never existed in science and hence cannot ever be logically superseded.
A further complication for science education is that any version of a model (i.e. an expressed, scientific, historical, curricular, or hybrid model) is placed in the public domain by use of one or more of five modes of representation.