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Chemistry Education Research and Practice, 14 2 , Towns, M. The biochemistry tetrahedron and the development of the taxonomy of biochemistry external representations TOBER. Chemistry Education Research and Practice, 13 3 , Yang, M-J. Journal of Science Education. Open Journal Systems. Journal Help. User Username Password Remember me. Notifications View Subscribe. Font Size. Information For Authors.
The prediction was that this would help the perception filter to select more efficiently from the new information in the lecture course, thus reducing potential working memory overload.
In turn, that would generate better understanding. Indeed, the study showed some quite bizarre behaviour as students tried to avoid the discomfort associated with the feeling that they were not coping. This was a matter of concern, given the expense of laboratory work in terms of staffing, time and resources. Working memories were simply being overloaded, leaving no capacity for any thinking or understanding.
The information processing model predicted, again, that working memory overload would be reduced if the perception filter was able to operate more efficiently. This led to the pre-lab.
A pre-lab is a short exercise completed before the lab where the underpinning ideas were revised, the background to the experiment s outlined, student completing various tasks to ensure understanding. This meant that, on entering the laboratory, the student had a much clearer idea what they were doing, and why , as well as knowing the key observations they needed to make, and why.
In addition, anxiety was reduced. Indeed, in the chemistry study, projects were introduced into the laboratory, giving the students an opportunity to apply their understanding as well as working in small groups to consider some social application of the chemistry involved.
This gave the added advantage of offering experiences in the way teams of scientists work together to solve problems, typical of how the sciences actually work. Interestingly, the extra time needed to complete the pre-lab exercises generates an even greater gain in time in the actual laboratory, giving time for other activities — hence the projects being possible. School laboratories are somewhat different but, even here, the pre-lab idea was extended in a novel way.
These were NOT designed to replace hands-on laboratory work but to act as a preparation for teachers a form of pre-lab who were about to be required to use laboratory work in schools, practical training being difficult, given that the students were scattered across a very large nation.
This model shows good prospects for developing countries. Numerous group exercises were created and tested with students, at both school and university levels. What research evidence showed from the various studies was that important skills and attitudes did develop.
Group-work allows the development of key skills like:. However, the information processing model does not suggest that the group work structure will reduce working memory overload: members work collaboratively but each has their own working memory. Figure 5 summarises the main findings from a large number of studies, many directed by Johnstone.
If we look at learning overall, then the work Johnstone directed has shown that the working memory holds a central and critical role in seeking to develop understanding. Given the highly conceptual nature of the discipline of chemistry, this offers the key for teachers as we seek to enable students to move forward successfully Figure 6 :.
We shall look at a few of these. Arising from his long experience in understanding why many students find understanding chemistry so demanding, he developed a very simple model Figure 7. Chemistry can be seen as having three levels of thought. There is the chemistry we can see, touch and smell. We try to represent and summarise what is happening using various symbolisms this include equations as well as various mathematical representations.
There is also our attempt to make sense of what we observe by developing insights based on entities that we cannot see: atoms, molecules and sub-atomic particles. This model is often misunderstood. This is simply because of the limitations in the capacity of the working memory.
He argued that, in the early stages in learning chemistry, we must be very careful not to attempt to bring in explanations and representations until the descriptive aspects are well established. The young learner at school and university, meeting ideas for the first time, with a limited working memory capacity, simply CANNOT work at all three levels at the same time Johnstone, As teachers, we need to focus on one level at a time , until the students are secure in their understanding.
Some examples illustrate this. At early school stages, there is an enormous amount of chemistry that can be discussed, basing things simply on what the young learners see in their experimentation, and then developing patterns and insights from this Reid, Once this is well established, the symbolics can be gently introduced and, later, interpretations involving the sub-micro explored.
One area where this was explored was in the learning of organic chemistry. For a student to grasp the descriptive, the representational and the molecular at the same time is asking the impossible. What research shows that, if the students have a good grasp of the descriptive with the use of simple molecular equations , the mechanistic can be built on this foundation at university.
Thus, mechanistic approaches should not be introduced until the the fundamental principles are well established. In essence, we need to ensure that fundamental ideas are well established before we start to bring in more ideas. This is almost certainly a major factor that makes the study of chemistry unattractive in some countries. When a learner has the fundamental ideas well-established, then these ideas are being grouped together to make coherent sense and, thus, occupy less space in working memory the principle of chunking : Miller, This leaves capacity to build on further ideas.
Where biology has an advantage is that much more can be covered at the descriptive level especially at school stages before it is essential to invoke the other levels. However, mathematics faces similar problems to chemistry in that many levels are needed quite early in learning. The triangle model has proved to be powerfully useful. Nonetheless, it is sad that this kind of insight does not appear in teacher education courses.
This raises questions about whether the education world really takes education research seriously Read, The evidence shows that most entering school teaching copy the way they were taught at school El-Sawaf, , evidence from research playing little part. In the s, Johnstone was required to write the preface of a commissioned monograph entitled, Creative Problem solving in Chemistry Johnstone, Facing this task, he realised that he did not really know what he meant by a problem or what problem-solving really was.
He came up with a very simple, yet powerful, analysis. In every problem in every area of life, there are three factors involved: what we know, the method to be used, the goal for the problem. It is very insightful to watch motor mechanics faced with a car that will not start. They know things about how an engine works or can be made to work , they have various tests they can apply and various tools they can use.
Their goal is simple: start the engine. What Johnstone realised was that, in any problem in chemistry, we either know everything we need to know or do not , we either have or do not have a known method to solve the problem, we know clearly what the goal is or the goal is unclear. This leads to eight types of problems Table 1 :. Eight problem types Johnstone, We provide the data, the students have been taught the method, the required goal is specified Bennett, However, in real life, most problems are not type 1.
Often, we do NOT possess all the information we need. Often, we do NOT have some set method to apply. In addition, in many areas of life including many areas of chemistry we are not quite sure of our destination! Johnstone never suggested that there is any hierarchy of difficulty. Thus, he stated quite clearly that these are simply eight different types of problems: difficulty and problem type are unrelated.
However, he did give us a simple way to classify problems. We can then analyse what we are doing with our students. Of course, there is a place for the algorithmic type of problem but there is also a place for a much wider range of problems, this reflecting more accurately the real nature of chemistry enquiry as well as wider life.
In a career that spanned over 50 years, Johnstone made a remarkable contribution to the world of chemistry education research. He never lost his love of chemistry.
He never lost sight of young learners as they struggle to make sense of the complex ideas that underpin any understanding of the molecular world and its interactions. He was always willing to assist learners as they tried to make sense of their world in understanding chemistry, whether he was working with a 12 year old school student or a PhD student grappling with complex data in an attempt to make sense of learning. His methods and approaches tended to be quantitative.
He replicated experiments related to learning and understanding. He never relied on questionnaires, focus groups or interviews in that all these can do is collate the opinions of others. He knew what was known, he knew the next stages needing enquiry and he directed students into these areas of research. Indeed, his research direction followed the established approaches that have proved so successful in the sciences and many other disciplines.
Of course, his target of enquiry was different. He wanted to explore and understand the complex nature of learning in the context of chemistry and related disciplines. Indeed, he took complex ideas and reduced these to simple models that are accessible and helpful. His methods were rigorous and powerful. Creativity was allowed to run free. Many of his research students started at one point and then went off in all kinds of directions during their research as findings pointed to new issues that were worth following up.
Generations of research students have expressed their gratitude for what he did for them and many have moved on to make their own contributions in their own countries.
He received numerous awards:. University chemistry departments in many nations have appreciated the impact, significance and relevance all his work. Sadly, that appreciation did not spread into wider education and it is regrettable that his insights have not found their way, in general, into schools of education. School teachers have often found the insights helpful but they lack the opportunity to change curricula or teaching methods easily, much being driven and often hindered by outside influences including high-stakes testing.
He has left a legacy of powerful insights, as well as a long list of publications, a few of which are referenced in this paper. He has left numerous areas where we, the next generation, must build on what he found. The goal for us has not changed. As teachers of chemistry, we want to equip the young people of the future to understand something of the remarkable contribution chemistry has made to our societies and cultures: to make chemistry exciting and accessible. For some, our goals will be to give these students a sufficient understanding so that they can carry forward the research enterprise to bring further understandings and, hopefully, benefits.
His major contributions can be summarised Figure 8. He has generated an agenda for teachers of chemistry Table 2 see Johnstone, a : Table 2: An agenda for action.
Finally, Georgios Tsaparlis had the privilege, in , to spend a sabbatical semester with Johnstone in Glasgow, which led on to an invaluable collaboration with him ever since. Ali, A. Understanding mathematics some key factors. European Journal of Educational Research , 1 3 , — Ashcraft, M.
Human memory and cognition. Search in Google Scholar. Atkinson, R. Human memory: A proposed system and its control processes. Spence Eds. New York: Academic Press. Bahar, M. Structural communication grids: A valuable assessment and diagnostic tool for science teachers.
Journal of Biological Education , 34 2 , 87— Bennett, S. Problem solving: Can anybody do it?. Chemistry Education Research and Practice , 9 1 , 60— Carnduff, J. Enhancing undergraduate chemistry laboratories. London: The Royal Society of Chemistry. Chen, W. Understanding physics in relation to working memory. Research in Science and Technological Education , 27 2 , — Chu, Y.
Genetics at school level: Addressing the difficulties. Research in Science and Technological Education , 31 1 , 1— The perception of matter as a continuous medium is quite a common misconception Nakhleh, Flores-Camacho et al. Often the experts use multiple representations to interpret a phenomenon. However, it is interesting to note that in the quoted study the two models most often used are incommensurable. Why the particle theory results so difficult for many students?
The history of the structure of the atom since the late 19 th and early 20 th century shows that the models of J. Thomson, E. Rutherford and N. Bohr evolved in quick succession and had to contend with competing models based on rival research programs. It is important to emphasize that evolving scientific models are not necessarily right or wrong, but rather increase in their heuristic and explanatory power.
In other words, Rutherford's model provided greater explanatory power as compared to Thomson's model, which does not mean that Thomson was wrong. Similarly, Bohr's model provided greater explanatory power as compared to Rultherford's model. This precisely shows the tentative nature of scientific knowledge and its importance has been recognized for science education Lederman, et al. Bohr's first model claimed to predict all the lines in the hydrogen emission spectrum. However, there was experimental evidence for a hydrogen series anomalous Pickering-Fowler ultraviolet series , where according to Bohr there should have been none.
The principal shortcomings of the Bohr model were that it could not explain the spectra of atoms containing more than one electron and the fine spectra into which spectral lines can be resolved using spectrographs of high resolving power e. Sommerfeld, however, considered Bohr's analysis of the hydrogen spectrum as only approximate as it was based on only one quantum condition, the quantization of the angular momentum.
Bohr's orbits were all in a plane, which was too simple an assumption. Bohr himself also recognized that the original quantum theory was incomplete.
In contrast, Sommerfeld specified not only the shape of the electron's orbit which by analogy with planets in the solar system, could be elliptical instead of circular but also its orientation in space.
Contrary to Bohr's picture, the electrons now moved in Keplerian ellipses and during their orbits, they penetrated the region of internal electrons, thereby causing a coupling of the revolving electrons. In other words, the Bohr-Sommerfeld model, considered the two-dimensional motion of the electron in its orbital plane. Treating the problem relativistically, Sommerfeld showed that as in the case of every periodic motion under the influence of a central force, the electron with rest mass m describes a rosette or, more precisely, an ellipse with a slowly precessing perihelion and with one of its foci at the nucleus.
Based on this basic idea of elliptical orbits, the Bohr-Sommerfeld model of the atom was widely accepted by the scientific community, as an alternative to Bohr's model. As a sequel to the discussion in the previous section, chemistry teachers would like to know if general chemistry textbooks present and discuss the Bohr-Sommerfeld model of the atom. In order to respond Niaz and Cardellini b analyzed 28 general chemistry textbooks published in Italy and 46 textbooks published in U.
Bohr-Sommerfeld model of the atom was presented satisfactorily by five Italian textbooks and three textbooks published in U. It is plausible to suggest that most general chemistry textbooks in this study simply ignore the Bohr-Sommerfeld model of the atom, and even if they mention the model, very few consider it as a manifestation of the tentative nature of scientific theories.
It is concluded that textbook authors and perhaps teachers either do not understand or do not consider the tentative nature of scientific knowledge to be important. In order to convince teachers of the importance of this model and how philosophy of chemistry can enhance our understanding we reproduce an example of a satisfactory presentation from one of the textbooks: Arnold Sommerfeld proposed an ingenious way of saving the Bohr theory.
He suggested that orbits might be elliptical as well as circular. Furthermore, he explained the differences in stability of levels with the same principal quantum number, n , in terms of the ability of the highly elliptical orbits to bring the electron closer to the nucleus Figure Thus, the highly elliptical orbits would have the additional stability … The s orbit, being the most elliptical of all in Sommerfeld's model, would be much more stable than the others in the set of common n … The Sommerfeld scheme led no further than the alkali metals.
Again an impasse was reached, and an entirely fresh approach was needed Dickerson et al. Some of the salient features of this textbook presentation, that can help in the formulation of a philosophy of chemistry are the following: a Bohr's model of the atom despite its drawbacks could be saved; b Sommerfeld's proposal was considered to be ingenious; c Postulation of elliptical orbits Bohr-Sommerfeld model could provide additional stability and this was supported by empirical evidence; d Despite its success, Bohr-Sommerfeld model of the atom did not go beyond the alkali metals; e Progress in science often leads to an impasse contradictions and consequently a fresh approach is called for.
This study shows that learning chemistry is difficult for many reasons. This study has shown that as atomic models change Thomson, Rutherford, Bohr, Bohr-Sommerfeld we need to provide our students with a scenario in which one model is superseded by another for reasons that can be presented explicitly and in a concrete fashion. Consequently, although visualizing atoms is difficult Johnstone's triangle , we can convince our students with arguments that are closely linked to experimental evidence.
In this context, content of the textbooks plays a major role as they often become the chemistry curriculum cf. No wonder, Bent considered that besides the textbooks, the most important models in teaching chemistry are chemistry teachers themselves.
These models, of course, can be strengthened by providing teachers with an overview of the philosophy of chemistry. I am grateful to Mansoor Niaz for advice and suggestions that substantially improved an earlier draft of this paper.. ISSN: X. Descargar PDF. Cardellini 1. Under a Creative Commons license. It is concluded that introducing some elements of history and philosophy of chemistry is conducive towards a better understanding of scientific progress.
Palabras clave:. Texto completo. Understanding the particulate nature of matter The particulate nature of matter is fundamental to almost every topic in chemistry and this explains the reason why its understanding is so important.
Tentative nature of scientific theories and models The history of the structure of the atom since the late 19 th and early 20 th century shows that the models of J. Why has the Bohr-Sommerfeld model of the atom been ignored by general chemistry textbooks?
Conclusions This study shows that learning chemistry is difficult for many reasons. I am grateful to Mansoor Niaz for advice and suggestions that substantially improved an earlier draft of this paper.
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