Particle model teaching

Vollebregt, M. J. (1998). A problem posing approach to teaching cm initial particle model. PhD dissertation, Utrecht University, the Netherlands, Utrecht. 

One of the important elements of the Model of Modelling framework is the consideration of the snbject s previous ideas as one of the experiences needed to support the proposition of the mental model. In this teaching situation, students previous ideas, mainly those related to the kinetic particle model, were essential to the inclusion of fundamental attributes in their models (e.g., the dynamicity of the chemical transformation). 

Apart from the introduction of the smallest particles, it is also necessary to discuss the inner space between the particles when discussing and teaching about the particle model The empty space is apparently missing in our particle model this empty space however is the unbelievable aspect in the discontinuum concept, much more so than the denomination of matter [10]. How can we change the lesson so that this unbelievable factor is convincingly accepted and understood by the students ... 

Albanese, A., Vicenti, M. (1997). Why do we believe that an atom is colourless Reflections about the teaching of the particle model. Science and Education, 6, 251-261. 

In general, studies of chemical kinetics at the secondary level emphasise qualitative aspects. At this stage, pupils (e.g. at ages 14-16) discuss the rate of different examples and investigate the influence of temperature, concentration and catalyst on the rate of reactions. Such aspects are explained with a colliding particle model. Chemistry teaching in Australia, Brazil, the Netherlands, New Zealand, UK and USA, for instance, adopts this approach. 

Vollebregt, M.J. (1998). A Problem Posing Approach to Teaching an Initial Particle Model. Utrecht CD-(3 Press. 

AN EXAMPLE DESIGNING AND VALIDATING TEACHING-LEARNING SEQUENCES ABOUT PARTICLE MODELS... 

We will now illustrate some aspects of previous considerations by referring to the design and the validation of teaching-learning sequences that we have developed about particle models (Meheut Chomat, 1990 Meheut, 1997). 

Designing teaching-learning sequences about particle models... 

So far, we have eompleted three teaching sequences. The areas are a qualitative particle model for gases (Andersson Bach, 1996), flie theory of evolution (Hagman, Olander, Wallin, 2002 Wallin, Hagman Olander, 2001) and geometrical optics (Bach, 2001). 

Buck, P., Johnson, P., Fischler, H., Peuckert, J. Seifert, S. (2001). The Need for and the Role of Metacognition in Teaching and Learning the Particle Model. In H. Behrendt, H. Dahncke, R. Duit, W. Grdber, M. Komorek, A. Kross P. Reiska (Eds.), Research in Science Education - Past, Present, and Future. Dordrecht Kluwer Academic Publishers, 225-234. 

Consider first of all a very simple elassical model for vibrational motion. We have a partiele of mass m attached to a spring, which is anchored to a wall. The particle is initially at rest, with an equilibrium position along the x-axis. If we displace the particle in the +x direction, then experience teaches us that there is a restoring force exerted by the spring. Likewise, if we displace the particle in the —x direction and so compress the spring, then there is also a restoring force. In either case the force acts so as to restore the particle to its rest position Xe-... 

The homework assignments related to everyday life provided excellent students feedback. Despite not being foreseen in the LON teaching plan, due to great student interest, we prepared an exhibition of different home-made models for the coal-burning reaction. Most students were very inventive in the selection of materials for home made models to represent chemical reaction at the particle level. [Teacher from School N° 3, additional lesson after Section 2]... 

Simplicity was never an attribute attached to the concept of nucleus in the way that it was attached for many years to the concept of atom. By the time the nuclear model of the atom was formulated, the atom was already known to be composite and at least some atoms impermanent. If the nucleus contained most of the mass of an atom, and if a radioactive atom spontaneously ejected pieces like a particles, then the nucleus must be where those ejected particles came from. Of course, we teach our students that nuclei are made of protons and neutrons. How did these particles come to be known Rutherford had a hand in their stories as well. 

With regard to teaching about ions and ionic bonding Barke, Strehle and Roelleke [19] evaluated lectures in the sense of hypothesis two by the introduction of atoms and ions as basic particles of matter based on of Dalton s atomic model (see Fig. 5.10 in Chap. 5) scientific ideas according to chemical structures of metal and salt crystals are reflected upon. 

These statements made by pupils after several hours of lessons drive every teacher to despair and make him or her wonder what went wrong in his or her teaching about small particles. The introduction of the particle concept is and remains difficult and cannot be mastered within a few school hours. Beginners start slowly and with many questions, arise at their first model concept of particles and their arrangement. 

Weninger [11] made the suggestion of using the word monad for the smallest particle of matter or the 16-proton atom as the name for the sulfur atom with the intention of avoiding misconceptions concerning differences in matter and particles sulfur should be the name of the matter, 16-proton atoms the name of smallest particles of sulfur. However, these suggestions were much cited but never imposed. Buck [12] also opposes concrete models or graphical descriptions of particles or atoms and distinctively asks how can one teach the difference between matter and atoms [12]. 

Teaching and Learning Suggestions. The scientific particle term has to remain associated to the sub microscopic level, it should not be used for small portions of material. Of course, one can speak of iron filings, small sulfur crystals, tiny water drops or of little gas bubbles at this level it should be no problem to avoid the particle term when talking about matter. Students will thereby realize that the smallest particle is reserved for the invisible area of mental models of matter, i.e. water particles, sugar particles, and ethanol particles (compare Sect. 4.1). 

Teaching and Learning Suggestions. The depicted empirical experiences show, that after lessons about the differentiated atomic model and ionic bonding, the existence of ions as the smallest particles of salts is only inadequately anchored in the young people s minds. Ion symbols cannot be satisfactorily applied by the majority of the test takers. Undifferentiated symbols like NaCl and HC1 in reaction equations are mostly used and the learners are left to their own devices how these compounds are structured by molecules or by ions [6]. 

These experiences have been described in literature of chemistry education for decades [6]. Only in exceptional cases has the teaching of chemistry been completely altered due to this criticism [9]. Students are not only given the atoms and correlative atomic masses based on the Daltonic model with the Periodic System of the Elements (PSE), but also important ion types (see Fig. 5.10). This special Periodic System graphically depicts and clearly arranges atoms and Ions as basic particles of matter [9] (see Fig. 5.10). Both spherical models of atoms and ions correlate to their sizes as measured by physicists. Christen [10] uses a similar system in his book for introduction to chemistry. 

Further standard voltages could be measured and placed into an electrochemical sequence with other pairs of half-cells, as can be found in many chemistry teaching books. The extent of the introduction of the hydrogen half-cell as a standard electrode can be determined in each individual lesson. If one consequently describes all redox reactions in relation to the metal sequence, redox or electrochemical sequence with ions and offers the students model drawings (see Figs. 8.3 and 8.4), then the electron transfer and the redox definition, in terms of involved smallest particles, becomes even clearer and the mixing at the language level of substances and that of particles can be effectively suppressed. 

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