Some reflections on the design of contextual learning and teaching materials 
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I think many teachers had the following experience. At the beginning of their teaching career, many of us were concerned only with our presentation skills on the podium and might have neglected students' level of understanding and participation. When the teacher discovered that the students did not understand the content of the course, he or she would repeat the same presentation. In the end, what started out to be a course with ample time could not be finished in the predetermined period of time. The time was spent, but the students' understanding is not deep, this method of teaching lacks efficiency. More experienced teachers may give students more room, arouse their interest to actively explore, and allow them to raise questions. The teacher will then focus on the questions and lead the students to solve their problems step by step. When the participation level of the students is high, learning becomes more efficient and more rewarding.
Modern education stresses on the participation of students; for if the students are not actively participating, no matter how wonderful, how complete the presentation is, it is not beneficial to the students. Campbell et al, 1994, when discussing science education, generalized the Salters' approach as
"The most important single factor influencing learning is the active engagement of the learner with the material. Obtain this  and teach by whatever methods to retain this engagement."
Traditional science teaching tends towards unidirectional didactic teaching and is not very efficient in encouraging students' engagement. Modern educators have proposed different approaches to encourage students to participate in a wider range of learning experiences, so as to nurture students to develop certain highlevel abilities like analytical, problemsolving and communication skills etc. The socalled contextual teaching and learning is only one of them. The writer is fortunate enough to participate in the secondary school physics curriculum reform in Hong Kong by working on the production of physics contextual teaching and learning trial materials for the Science Education Section of Education and Manpower Bureau. With this article, the hope is to share some of the reflections and experiences gained during the course of the production. The writer lacks profound understanding of education theory, and has no means of providing a thorough discussion on the pros and cons of different learning and teaching methods, nor is there any intention to dissect the method of contextual learning and teaching. The intention is simply to introduce the central ideas of contextual learning and teaching, so as to express some views on the development of physics education in Hong Kong. Limited by the inadequacy of knowledge on the writer's part, the point of view of this article may be crude, and may even contain errors. We hope that the colleagues of our profession would kindly point out our deficiencies.
Contextbased Learning and Teaching of Physics (物理情境教與學) is a very broad term. Generally speaking, it represents the use of events from students' and teachers' life, social, and cultural background as a platform to learn physics. Some less general views consider that contextbased learning and teaching of physics emphasizes the application of physics principles on different situations, as means to strengthen students' understanding of physics and broaden their perspectives. Different academics have different interpretations when talking about contextual teaching and learning. Of course, the core of their concepts also has a lot of areas in common, which is broadly summarized as the following points.
Educators that encourage the use of contextual learning and teaching all consider that this method can show to students the operation of physics in the real world and society, thus providing a more concrete and authentic picture for the learning of science. The method can also provide learning activities that make use of the living environment as a platform, getting students more involved in learning, developing their generic skills like problem analyzing and solving, and communication etc. Similar approaches have been utilized in Britain, America and Australia etc. In the 2003 physics curriculum reform in Hong Kong, efforts have been made to allow more time and freedom for teachers and students to attempt different modes of learning, especially contextual learning and teaching, the use of datalogger and science article reading. If we consider that the application of contexts has its value in achieving the benefits mentioned above, then it is extremely important to develop contexts that are useful, reasonable and interesting, at the same time decide upon clear learning objectives, carefully edit and arrange the content of learning and teaching and the corresponding activities, in order for this method to be most effective.
During the course of physics teaching, we, to a certain extent, hope to use examples of certain contexts to let students understand how physics is applied in the real world, or let students take part in certain explorative activities. In traditional physics teaching, teachers make use of idealized examples to avoid the complications of the real world, so as facilitate students' grasp of the main point of a physics problem. For example, we may use "a toy car sliding down a frictionless incline plane" as an example to teach the resolution of force as well as Newton's Second Law; we may use the example of a "uniformly accelerating elevator" to teach the application of free body diagram etc. These examples are not realistic, but are very effective in transferring basic physics concepts. Nevertheless, if we use them as contextual examples for students to explore, the students may get a bit confused, especially when they want to do some quantitative analysis in these situations. For example, the student may want to measure the change of his weight inside an elevator using a scale, but the acceleration of the elevator is constantly changing, and what he observed may only be the disorderly swinging of the needle of the scale. That is why traditional physics teaching is complemented by experiments to avoid these unnecessary complications. Students are told to observe meticulously the physical phenomena taught in class in a wellcontrolled environment. But in this way, the connection with the real world is easily lost.
To find a good context for contextbased learning and teaching in physics is by no means easy. There are times when the complications of the real world make it difficult for the teacher to introduce the physics content he wishes to teach through a real situation. In the real world a phenomenon almost always depends on a number of factors, many of which may be out of the syllabus of secondary school physics, and students may have no way of understanding. Even if the factors are understandable, students might be confused by their complicated relations. Contexts of this kind make students, and at times even experienced teachers difficult to demonstrate succinctly and clearly the main point of learning and the logical relationship therein. If the context is the means that serves only to achieve the learning process and the acquisition of physics knowledge as the ultimate aim, this kind of contexts would not benefit learning, on the contrary, it would obstruct the learning process. The first premise of utilizing context should be, the context is a learning tool used to increase the involvement of the students, provide them with a wide range of learning experience, as well as to develop their ability to solve realworld problems, and should not be turned into the content of learning and teaching itself or its burden. Certain physics concepts that are difficult to be expressed in everyday language should be best explained using traditional teaching method. Inappropriate use of contextual examples just for the sake of applying the contextual approach would only further confuse the explanation and frustrate both the teacher and students.
The above discussion seems to put teachers in a dilemma: an overly simplified and theoretical discussion cannot connect physics principles with everydaylife phenomena, whereas excessive contextual descriptions will cause one to get lost in the complicated world of phenomena, hinder the acquisition of basic physical principles, let alone problem solving. Neither of the approaches is helpful.
How to choose appropriate and useful contextual examples is quite a complicated problem. In the end, whether the contextual examples are successful or not of course also depends on whether or not the learning objectives laid down at the beginning are achieved successfully. As a few basic principles, the author considers following points helpful when choosing contextual examples.
Point one is saying that contextual examples should be familiar to students. What makes an example familiar to students? It should be noted that, what we call familiar is sometimes quite personal, and will vary with the students' background, lifestyle and geographical environment. For example, teachers may use the traffic condition around the school to explain concepts like distance, displacement, speed and velocity. These physics concepts are of course universal, and the laws of physics involved are also generally true; but different schools have different locations, and the environment that students are familiar with are also different. It is of course ineffective to discuss the traffic condition of Aberdeen with students of a school in Tuen Mun. Textbooks from the overseas may have used certain contexts local there. Things like heating system or skis, for example, are unfamiliar to Hong Kong students. Gender differences may also affect the students' enthusiasm towards certain topics, for example, male students compared to female students may be more interested in the performance of automobiles and may be more enthusiastic when applying Newton's Laws to analyze automobile performance data.
The word "familiar" used here not necessarily means the events that happens close to the students. Certain social issues, or topics widely reported by the media, can also serve as appropriate contextual examples. A while ago, a few movies about the catastrophes of meteors hitting the Earth attracted much attention of students. Making use of this kind of topics to focus the students' attention back to serious scientific principles may bring unexpected benefits. For example, concepts like kinetic energy and momentum can be utilized for guiding students to estimate the destructive power of an explosion due to a meteor impact on Earth. The scene of a space shuttle liftoff appearing on television news can serve as a tool for teaching Newton's Second Law. The consumption of fuel means the space shuttle has a decrease in mass and would naturally bring out the relationship between inertia and acceleration of a system. In recent years, traffic accidents occurred frequently in Hong Kong, and the government installed crash cushion system at the divisions of highways. This is a good example to use when teaching the relation between force and time of collision. To find real data for these examples is not difficult, and it would also satisfy the third point in our guideline, namely, the requirement for quantitative analysis and problem solving. Some teachers like collecting newspaper cuttings on physicsrelated news. This kind of information can turn into good teaching material after appropriate editing, and is certainly helpful to students. The teacher's ability in guiding the students is crucial in the application of contexts. The teacher should be constantly able to flexibly utilize examples that are familiar or attractive to students, or that serve to broaden the students' perspectives and bring out real science.
Point two stresses that the contextual example chosen should let students clearly and concretely observed the physical phenomena required to learn. Overly complicated situations and misleading examples should be avoided. What is considered clear? What is considered an overly complicated situation? This depends on the learning objective set initially, and in relation to point 3, the criterion of quantitative analysis. Let's consider the example of weight change inside an accelerating elevator again. As mentioned above, it is not a very good contextual example for students to explore, because in reality student inside an elevator cannot easily observe a stable change in his own weight, and hence it is very difficult to obtain data for quantitative analysis. Perhaps we can use tools like datalogger to record how the weight changes inside the elevator, and then analyze the seemingly random data to obtain results consistent with Newton's Laws. However, whether this learning process is effective or not depends very much on the learning objective of the activity. If the learning objective is only the application of the Newton's Second Law and the use of free body diagram, but students are required to do extensive data analysis, the emphasis of this activity may have been misplaced. The concepts of freebody diagram etc. are already quite difficult for an average S4 or S5 student. If the students are also required to handle extensive data analysis, they may easily get lost in all kinds of techniques and fail to understand the basic physics concepts. On the other hand, a S6 student who is already familiar with Newton's Laws can work on the activity as a mini research project. The main learning objectives may no longer be basic concepts like Newton's Laws, but experiencing a series of exploration processes, learning data analysis and calculation techniques. He may discover that the activity satisfies his learning objectives.
Thus the choice of context depends on the background and learning objectives of the students. For an average S4 or S5 student, the learning objective is mainly basic physics concepts and learning the method of solving problems. The choice of context for exploration should be as simple and straightforward as possible so as to avoid the introduction of unnecessary details that may cause confusion. It should be noted that here we are talking about examples for contextual exploration, which includes the elements of observation, analysis and experimental activities. Therefore, a bad choice for an example for contextual exploration may not be a bad choice for a teaching example. We can still utilize traditional teaching method and use "uniform accelerating elevator" to teach Newton's Second Law because it is a simple and precise example. Telling students to experience how their weight changes inside an elevator is also beneficial, as long as students are reminded that in the real situation, the acceleration is not uniform but will change in a complicated way, and therefore it is not easy to perform quantitative analysis.
In fact, the misplace of emphasis on the learning procedure instead of the objective due to unclear learning objective can be seen not only in contextual learning and teaching. Even in the old curriculum, similar situations exist. Every time people introduce a new teaching method, there is a tendency to emphasize its advantages, concentrate on its methodology instead of its effectiveness. For instance, the old physics curriculum emphasizes experiment, and so the ticker tape timer was very frequently used in the section of mechanics. The time students spent on cutting ticker tapes, learning the principles behind the construction of tape charts may be even more than the time spent on learning the equations of uniformly accelerated motion. Sometimes students do not understand the underlying principles, and so they force themselves to remember the method of producing the ticker tapes and the experimental results just to cope with public examination. Under Hong Kong's examoriented culture, we must pay attention to the load that students have to bear when undergoing any education reform. This is why during the course of designing education plans or education materials, educators must continuously rethink whether the approach used can straightforwardly and succinctly achieve the learning objectives and not narrowmindedly diving into the list of techniques. This of course needs the complementary of the public examinations.
The last thing needed to be point out is that, the choice of context affects greatly the accuracy of expression of physics concepts. Some people think that in order for contextual learning and teaching be attractive for students, very interesting examples must be used. However, contextual learning and teaching is not the same as learning and teaching with fun; and interesting examples may not always be beneficial or useful. For example, young people like reading comics, so we may try to use the example of a comic character with herculean strength punching someone into midair at a high speed to teach about the relation between force and acceleration in Newton's Second Law. This example is interesting but unrealistic, and can easily lead to misunderstanding. The reason is that this example is not observable in the real world, and it can easily cause students to confuse between "a very high acceleration" and "a very high velocity", Students may end up acquiring the wrong concept that a large force will result in a high speed, without getting the concept of acceleration. In fact, there are quite a few good reallife examples that can accurately bring out the relation between force and acceleration. For example, consider a sedan and a sports car accelerating on the same highway. The highway has a speed limit, but because the sports car has a higher acceleration, it can get to this speed in a shorter time then the sedan. The change of speed as appear on a car's speedometer, the force that the passengers feel at their back when a car is accelerating, are all observed and experienced in the students' daily lives. The change on the speedometer allows students to easily distinguish that acceleration is concerned with the rate of change of the velocity but not the size of the velocity itself. In their living environment, students can easily find sufficient data on the acceleration and horsepower of cars in for doing analysis. Therefore this reallife example can much more accurately express the meaning of Newton's Laws than the former example. As for whether it is interesting and attractive to students rests mostly on the presentation technique of the teacher.
There are times when we overly desire to contextualize a physics problem. If we are not careful in doing so, we may create unrealistic or misleading examples. In some popular secondary school physics textbooks, you can easily find examples like the following: a question on heat has the answer of eating ice cream decreases the body temperature of a person by 0.43 _{ }_{ } ; a question on mechanics asks students to use the collision time of a car to calculate the impact force experienced by a passenger; another question states the mass of a car as 50 kg; another question says that a 10 kg rocket will weight 16 N on the moon. Some of these questions involve wrong physical concepts, other involve unrealistic data and situations. Note that a lot of textbooks use words like "assume" to simplify the question, there is no major problem in doing it this way. But giving students examples that sounds real and are full of contexts could really cause misunderstanding, especially when they are not very clear about the physics concepts. In fact in this informationrich age, it is not difficult to find real situations and reasonable data on the internet. After all, you probably do not want to see your children eating ice cream during a fever with the purpose of lowering the body temperature!
Different teaching methods all have the same aim of letting students involve in learning actively, not only to increase their knowledge, but also to nurture certain learning habits that will have lifelong benefits to them. Contextual learning and teaching is only one of the ways. Whether it is effective and practical under the culture of education in Hong Kong still need to be tested through a lot more trials. The Education and Manpower Bureau and the Department of Physics, The Chinese University of Hong Kong, have produced a number of contextual learning and teaching tryout resources including the "Contextual Physics" web site (this web site) and "Contextual Physics in Ocean Park" web site. The address of the latter is
The author hopes that physics teaching colleagues at large would provide more feedback and suggestions to resources like these, so as to facilitate the production of contextual teaching and learning resources that are more suited to the learning and teaching environment of Hong Kong.
Brooks, J. G., and Brooks, M. G. (1993) In search of understanding: the case for constructivist classrooms. Alexendra, VA: Association for Supervision and Curriculum Development
Campbell, B., Lazonby, J., Nicholson, P., Ramsden, J. and Waddington, D. (1994) Science: the Salters' Approach  a case study of the process of largescale curriculum development, Science Education, 78 (5), 415447, 1994
Elaine B. Johnson, Ph.D. (2002), Contextual Teaching and Learning: What is it and why is it here to stay. Thousand Oaks, California: Corwin Press Inc. A Sage Publication Company
Hart, Diane (1994), Authentic Assessment: A Handbook for Educators. Menlo Park, California: AddisonWesley Publishing Co.
Lubben, F., Campbell, B. and Dlamini, B. (1996) Contextualizing science teaching in Swaziland: some student reactions, Int. J. Sci. Educ., 1996, Vol. 18, No. 3, 311320
Mueller, J. F., Authentic Assessment Toolbox
http://jonathan.mueller.faculty.noctrl.edu/toolbox
National Conference on Teacher Quality  Exemplary Practices in Contextual Teaching and Learning
http://www.ed.gov/inits/teachers/exemplarypractices/c3.html
Whitelegg, E. and Parry, M. (1999) Reallife contexts for learning physics: meanings, issues and practice, Phys. Educ., Vol 34 (2), 6872, March 1999
Wiggins, G. (1990) The Case for Authentic Assessment, ERIC Digest
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