Dimitris Psillos
University of Thessaloniki, Greece

Méheut's paper is concerned with facilitating student's understanding of some aspects of the structure of matter. This is an important teaching and learning issue since models regarding the structure of matter are included in several science curricula world wide. Méheut takes into account results on students' conceptual difficulties and historical developments of atomic models in attempting to develop research based teaching which is adaptable to students' reasoning. In this sense Méheut meets with several other researchers who attempt to develop small scale thoroughly investigated curriculum projects which may contribute to the elaboration of a content based theory of teaching and learning science.

The specific characteristics of Méheut's proposal are related to her epistemological and learning assumptions put forward either explicitly or implicitly in her paper. For Méheut, modeling of the phenomena is an essential function of science as a discipline which should be fulfilled by science teaching too. This position is reflected in the materialization of her teaching sequences in which the models suggested to the students are conceived as "tools to unify descriptions and predict phenomena". These tools have to be taught to the students, they are not supposed to derive from observation of experimental data, and this is one distinctive characteristic of Méheut's approach as compared to other sequences on this and other topics.

Méheut suggests two types of models for the structure of matter both aiming at enabling students to develop a unifying account of a set of observable phenomena. The first, simple model, involves students in interpreting physical transformations of matter as changes in the spatial organization of immutable particles while the second, more advanced model, makes potentially possible the interpretation of thermoelastic properties of gases by the students. In essence, Méheut suggests the explicit linking of the proposed models to a corresponding experimental field, an approach taken also in the teaching sequence on electricity presented in this chapter. I believe that this is an important development to which considerable attention should be given in both research and teaching since it may facilitate our understanding of the cognitive demands put on the students as well as the limits of the taught knowledge. An issue emerging from such a position is how to design teaching sequences leading to increased levels of understanding. In the topic of electricity I suggest that a hierarchy of models, corresponding to enlargement of the experimental field, should be presented to the students. In the topic of the structure of matter a similar approach seems to be taken, in which simple and advanced models form a developmental hierarchy rather than independent teaching pathways.

Another important issue in Méheut's paper concerns the representation of scientific knowledge specifically for teaching and learning purposes. In both sequences qualitative models are used for introducing conceptual scientific knowledge and it is as far as that, that the models on the structure of matter go in line with the aims of teaching. In a broader perspective, I consider that students should acquire a capacity to handle qualitative or semi quantitative models and then they should be taught quantitative ones which are compiled forms of knowledge distant from students' reasoning.

Understanding the structure of matter involves students in handling abstract models so Méheut uses still pictures and parametric simulations to "concretize" microscopic entities and process. I consider that relating such "concretized" models to simple experiments may provide the experiential basis which is necessary for meaning making and for constructing links between observable phenomena and underlying microscopic process. Finally, another crucial issue is how to make students put into play microscopic models instead of complying with phenomenological explanations. It appears from Méheut's paper that students initially carry out experiments, afterwards they are taught aspects of the models and then they are guided by appropriate questions to provide explanations of the observed experiments in terms of the models. This is a rational approach in line with Méheut's learning assumptions the learning results of which are encouraging. An alternative could be the creation of a need in the students  to be involved in such a constructive activity. In the sequence on electricity meaningful cognitive conflict is a strategy used for engendering a search by students for an explanatory microscopic mechanism. One wonders whether such a strategy would be effective in the topic of the structure of matter as well.


Section E,  Comments on E3  from: Connecting Research in Physics Education
with Teacher Education
An I.C.P.E. Book © International Commission on Physics Education 1997,1998
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