Modelling in science lessons: Are there better ways to learn with models?

School Science and Mathematics, Dec 1998 by Harrison, Allan G, Treagust, David F

Concept-process Modelling

The most abstract models are concept-process models. These are process thinking models for understanding and applying important concepts, like physical and chemical equilibrium, biological classification, and current flow in network circuits. Carr (1984) pointed out that concept-process models, like the three models of acids - they are sour and react with metals to produce hydrogen, Arrhenius acids produce H ions, and Bronsted-Lowrey acids are proton donors - confuse many chemistry students. Some of the models used in different parts of the science syllabus are even contradictory; for example, the use of conventional current (a flow of positive charge) in physics clashes with the flow of negative electrons used in electrochemistry. And then there is the conflict between the four models of oxidation-reduction. Which is oxidation: gain of oxygen, loss of hydrogen, increase in oxidation number, or loss of electrons? Each model describes oxidation, but often students cannot understand why the teacher has introduced another model with an opposite action (loss instead of gain) for the same process. Maybe we should be more surprised when students are not confused by this model swapping!

Summary

The preceding evidence suggests that teachers may enhance their students' learning by using the model typology to assess the conceptual demands of the analogical models they plan to use in their lessons. From an Ausubelian perspective, model-based learning should be most effective when learning builds on what the student already knows. If this be the case, introducing complex maps and diagrams, simulations, and concept-process models containing multiple simple models before the students have mastered the analogical nature of the simpler models will be detrimental. Research supports teaching students simple model forms before advancing to the more difficult and abstract models. Learning to model also should be overtly social and involve discussion and negotiation of meaning, because this provides the best opportunity for each student to construct the desired knowledge. Such an approach provides formative feedback to students, while helping teachers monitor their students' learning.

Multiple Explanatory Models

Many science concepts depend on multiple models for their description and explanation. The more abstract and nonobservable a phenomenon, the more likely it will require multiple models (e.g., atoms and molecules, forces and nerve circuits), because each model elaborates but a fraction of the target's attributes. In many cases, the sum of the models is less than the whole phenomenon for two reasons: (a) the concept itself is not fully understood, and (b) the models tend to overlap. There are sound reasons why no single model can fully illustrate an object or process. If it did, it would be an example not a model (Bent, 1984). Expert teachers mostly use models to stress and explore important and difficult aspects of a concept, and this is best achieved by oversimplifying the model to emphasize key ideas (e.g., the simple tube for an earthworm's gut). A series of simplified models can be used to explain, one at a time, the key ideas. Multiple simplified models also signal to students that no individual model is "right."