PROCEDIMIENTO PARA EL MANEJO, TRATAMIENTO Y SEGREGACIÓN DE DESECHOS RADIACTIVOS

The word model has a range of meanings within the scientific and science teaching communities, Gilbert, Boulter, & Rutherford (1998b) and Gilbert, et al. (1998b) and Gilbert, Boulter, & Elmer (2000) see Figure 2.3. Models themselves are in many ways the stuff of science:

A model in science is a representation of a phenomenon initially produced for a specific purpose. As a “phenomenon” is any intellectually interesting way of segregating a part of the world-as- experienced for further study, models are ubiquitous.

Gilbert et al. (2000, p. 11)

The everyday understanding of models, usually a physical scale model, is also present in science teaching. Examples are models of torsos in biology; ball-and- stick models of molecules in chemistry and vibrating ball bearings as a model of solids, liquids and gases in physics and chemistry. These physical models also share other characteristics.

The models are models of things that happen or exist in the real world, in other words phenomena. The models attempt to show aspects of the physical world in another way: a plastic model of a torso, which is roughly to size or a plastic or metal model of atoms and molecules which is greatly magnified. The models are

The vibrations in the kinetic model are to show the random motion of the particles in a gas, which is analogous to the macroscopic temperature of the gas. Other models can be more abstract, for example the mathematical models which dominate physics dealing with ideas like energy and force which are abstract.

Models and analogies

Models and explanations of models permeate the school science curriculum. Harrison (2008c) argued that models are based on analogies. An analogy is a comparison of the way that two things are like one another. To explain a target concept, the teacher starts with a familiar, and hopefully well-understood, system which is called an analogue. Ratcliffe (2001) explored these ideas in relation to teaching about atoms and molecules in the early secondary school.

Harrison‟s (2008c) link between models and analogies also contained the warning that the model or analogy is not the phenomenon itself, but a representation of the phenomenon. The warning that a model is not the phenomenon had also been expressed earlier by Gilbert, Boulter, & Rutherford (1998a, p. 95). There can be a tendency among teachers and learners to confuse the model with the reality which it represents, which leads to the misconception that understanding the model means that the phenomenon has been understood. This naïve approach ignores the fact that the analogue only corresponds to some aspects of the target. Wellington & Ireson (2008, p. 8) and Harrison (2008b) Chapter 4 discussed the necessity to use different models and to examine the limitations of the models and where they break down to try to avoid conflating the model and reality.

Gilbert & Boulter (2000, p. 12) identified nine different kinds of model which may be used in science teaching. The scientific model about a topic is the consensus view held by the scientific community. The scientific model may be controversial in the wider community. For example, the theory of evolution is well-accepted and uncontroversial among the community of evolutionary biologists and the wider biological and scientific community, Jones & Reiss (2007), but controversial among

sections of the general public. Dawkins (2009) has recently tried to reduce public scepticism about evolution.

However, a scientific model must begin as a private mental model that is shared by becoming an expressed model. An expressed model which is agreed among a community will become a consensus model. A consensus model within the

scientific community would become a scientific model. Some scientific models will be taught to learners, probably in the simplified form of a curricular model. As scientific models are superseded by new scientific models, the old version would be referred to as a historical model.

A teaching model, or sequence of teaching models, is the simplified and educationally justified approach used by science teachers to meet syllabus

requirements. Teaching models may be developed by teachers or learners and draw on a range of curricular, historical and consensus models as appropriate. Teaching models may be previous consensus models, for example Bohr‟s 1913 model of the atom, described by Nave (2006), is used in the Scottish Higher Physics syllabus, SQA (2004b, p. 8). Pupils may be introduced to a sequence of progressively more scientifically accurate models as they mature, following Bruner‟s (1986) ideas about the spiral curriculum.

Hybrid models are used for teaching and draw on the different models described above as appropriate. However, to use models effectively in the classroom, teachers have to develop an appropriate model of pedagogy which draws on a wide range of knowledge. The aim of teaching is to have a learner‟s private mental model, which can only be accessed via some form of expression, agree with the target teaching or curriculum model.

Figure 2.3 is a concept map which shows the links between the different kinds of models described above. Figure 2.3 allows a visual exploration of the links between the different kinds of models discussed above. Figure 2.3 shows a

complex web of connections between the different types of model and illustrates one of the reasons why using models in science teaching can be difficult.

Figure 2.3 Concept map showing the inter-relationship between different types of models used in school science. The concept map was developed from Gilbert, et al. (2000).