Students’ misconceptions particle model

A teacher may ask his or her students about their understanding of the particle model of matter. If the teacher needs a written questionnaire, he or she could use a diagnosis test created by Kathrin Brockmann [22] at University of Muenster. She developed the test Particles of Matter , utilizing some of the very well-known misconceptions held by most students. Finally, she evaluated this test with about 160 German students aging from 13-15 in the 7th grade [22]. 

The basic particle model poses challenges. To the eye, matter appears to be continuous and imagination is needed to think in terms of extremely small, discrete particles. Initially, some students may construct an image of particles embedded in continuous matter. Unfortunately, textbooks sometimes show such images and talk about particles in a solid/liquid/gas, which could lead students astray. Here, the particles are not the substance, they are extra to it. Ideas of particle movement are consistent with this model since movement will be determined by the state of the continuous matter (for example, particles can move arovmd in a liquid). Identifying the particles with the substance helps to avoid such misconceptions, for example, sugar particles , water particles and oxygen particles . 

In their initial stndies, Pallant and Tinker (2004) found that after learning with the molecular dynamic models, 8th and 11th grade students were able to relate the difference in the state of matter to the motion and the arrangement of particles. They also used atomic or molecular interactions to describe or explain what they observed at the macroscopic level. Additionally, students interview responses included fewer misconceptions, and they were able to transfer their understanding of phases of matter to new contexts. Therefore, Pallant and Tinker (2004) concluded that MW and its guided exploration activities could help students develop robust mental models of the states of matter and reason about atomic and molecular interactions at the submicro level. 

Many school-made misconceptions occur because there are problems with the specific terminology and the scientific language, specially involved substances, particles and chemical symbols are not clearly differentiated. If the neutralization is purely described through the usual equation, HC1 + NaOH —> NaCl + H20, then the students have no chance to develop an acceptable mental model that uses ions as smallest particles. 

Ions in Precipitation Reactions. Grade 10 students of German academic high schools have learnt the atomic model and about the idea of the ion and ionic bonding in their chemistry lessons. These students saw precipitates of calcium sulfate from saturated salt solutions and have been asked to imagine the smallest particles in these solutions before and after the precipitation [6]. The expected ion symbols of the initial solution were correctly supplied in 50% of the cases. However, the other half of the student group has shown misconceptions of salt molecules or of electron transition in the formation of ions from atoms . With respect to the precipitation product, only 30% of the students provided acceptable structural models, the amount of misconceptions grew to 70% [6]. 

Summary. It is pointed out that, in order to avoid misconceptions, the introduction of ions is very important ions have been dealt with as basic particles of matter according to Dalton s atomic model (see Chap. 5). In order to understand the charges of ions and the change of ions and atoms by electron transfer, the differentiated atomic model with nucleus and electron shells should be introduced. With the assistance of a clear terminology, it is easy to formulate half-reaction for the oxidation and reduction steps, the number of electrons to be transferred can be clearly recognized. Finally, if mental models -for instance, from involved atoms or ions in Galvanic cells or in batteries - are relayed and drawn by the students themselves, then they could more easily see through the redox processes or even perhaps be able to repeat them independently. In all explanations, one should pay attention that the observations should be done at the substance level, but that the interpretations and discussions of reaction equations should consequently take place at the level of the smallest particles as atoms, ions and molecules. 

Problem 3. In this task, students have to show their mental model of well-known copper sulfate compounds by drawing symbols of the involved particles in given models of beakers. The diagram of Problem 3 represents one possible correct answer [9]. Only a few students could provide acceptable mental models for all three items, and more than two-third of the participants made severe mistakes they exhibited many misconceptions (see Fig. 9.6). 

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