Models misconceptions about

The thorough study of many biological systems has involved purification of one or more of the system components. Unfortunately, there are a large number of misconceptions about the manner in which to develop a successful purification scheme. One systematic way to develop such a scheme is discussed here using proteins as a model, but the same considerations, perhaps in different terms, would apply to any biologically significant molecule. The five basic steps of purification are as follows ... 

The performance of two-parameter cubic equations of state with the conventional van der Waals mixing rules (1 PVDW model) is relatively well known and is presented here mainly for reference, but also to indicate certain misconceptions about this method. The results presented in this section were obtained using the computer program VDW provided on the accompanying diskette. The program details are presented in Section D.3 of Appendix D. 

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]. 

A common misconception about resonance is the notion that a molecule such as ozone somehow shifts quickly back and forth from one resonance structure to the other. Keep in mind that neither resonance structure adequately represents the actual molecule, which has its own unique, stable structure. Resonance is a human invention, designed to address the limitations in these simple bonding models. To extend the animal analogy, a rhinoceros is a distinct creature, not some oscillation between mythical griffin and unicorn ... 

For the most part, much of the debate in the past between MO and VB theories versus graph theory has illustrated misconceptions about chemical graph theory. The two theoretical methodologies, quantum chemical and graph theoretical, consider somewhat different questions or different aspects of the same problem and are thus complementary to one another rather than competitive. So while MO and VB theories are, and will remain, about the nature of the chemical bond , we can say that Clar s model and chemical graph theory are, and will remain, about the nature of the chemical structure . Clearly, we need both the quantum chemical tool and the graph theoretical ideas to be combined in order to advance our understanding of complex chemical systems. 

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. 

Particle Model of Matter. In chemistry, one goes with the premise that all matter is composed of submicroscopic particles, namely atoms or ions. They can appear isolated (atoms in noble gases), but mostly combined in groups of atoms or ions. They more or less form large aggregates with specific characteristics (e.g. metal crystals or salt crystals). The variety of matter is created by the many possible combinations and structures of a limited number of elements, of atoms and ions [15]. With respect to this, misconceptions can only be school-made because one needs special lessons about the particle model of matter or Dalton s atomic concept before one develops misconceptions related to these concepts. These discussions will follow in Chap. 4. 

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]. 

Some students misconceptions (see Fig. 9.6) show that solid white copper sulfate is described without the involved ions. The name of copper sulfate pentahydrate makes many students think of the coordination number 5 -although in lectures they have all heard about the octahedral coordination of the copper ion (see Fig. 9.2). Some don t even take into account the coordinated copper ion but only of CuS04 groups surrounded each by 5 I IzO molecules. The blue solution is mostly described by ion symbols - but only four students out of 60 have model images concerning complexes either with the coordination 6 (see Fig. 9.2) or with the coordination 4. Therefore, we will discuss the way in which the students should be taught and should learn coordination chemistry in their lectures (see Sect. 9.2). 

Behavioral expectations about the automated controller behavior are formed based on the human supervisors knowledge of the input to the automation and on their process models of the automation. Gaps or misconceptions in this model... 

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 . 

Presenting the idea of the chemical equation as a very useful model that can help us summarise what is going on in reactions, and which does a good enough job for most reactions, will both enable students to see the value of the formalism and stop them making unfortunate generalisations about all reactions going to completion (which could then later act as a misconception when they meet reactions that do not fit the model). 

This scheme is actually much more comphcated than the scientific model of silver ions sticking to chloride ions because of their opposite charges (Figure 4.7) and illustrates just how tenacious some misconceptions can be once they have a hold of a student s imagination. You can download a diagnostic task to identify common alternative conceptions students may hold about how bonds form in a precipitation reaction ( Reaction to form silver chloride ) from the Royal Society of Chemistry website (see the Other resources section at the end of this chapter). 

Students can end up thinking about chemical reactions with any number of faulty models - leading to confusion, misconceptions and frustration. In designing a teaching sequence it is important to... 

To conclude, we would like to point out two good things about MORE. In first place, MORE is able to understand deep misconceptions by a simple mechanism of context s semantics comparison. Second, because it is a theory, the student model is runnable. It is thus possible to know the consequences of the student knowledge by just executing the theory representing it. 

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