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Last Revised Nov. 27, 2000
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Using Images, Harry E. Pence, SUNY Oneonta, Oneonta, NY, firstname.lastname@example.org
(This brief article ws prepared for the Fall, 2000 issue of the Computers in Chemical Education Newsletter.)
One of the most powerful aspects of using presentation software for chemical lectures is the ability to show images and text (i.e. concepts) on the same frame. This is not merely a way to capture the students' attention but also a way to reinforce the learning process. In addition, carefully selected images play a special role in chemistry by converting abstract concepts into concrete representations. Some research indicates that understanding chemical concepts is based on the development of increasingly complex and useful images. To make the most effective use of presentation software, it is essential to better understand how to use images for teaching.
Educational research suggests that, in general, the combination of text and images can be a powerful educational tool. Images not only make a presentation more interesting, but the combination of images and text is easier to remember, especially if the two are presented in close proximity. Some psychologists suggest that this occurs because the information is coded into the mind in two different ways and so is easier to retrieve.
Images are particularly important in chemistry. In a 1987 article, Kleinman et al (1) reported that the level of sophistication of a person's chemical knowledge was closely related to the types of mental images that he or she used. They concluded that
Our study suggests that classroom instructional methods should consider that the ability of a student to understand chemistry may be related to the student's ability to develop specific images appropriate to the chemical concepts.
A.H.Johnstone has suggested (2) that chemistry is customarily taught at three different levels, microscopic, macroscopic, and symbolic. Changing back and forth among these levels is part of what makes chemistry difficult to understand. As he analyzes the difficulty that students have understanding science, he concludes,
Part of the problem rests with the nature of the science itself, but more seems to lie with the ways by which science is customarily taught.
One possible way to alleviate this problem is to use images to bridge the gap between the microscopic and the macroscopic worlds. Despite this, chemistry is a discipline that is rich in images, but it has traditionally been taught with few really useful images.
Presentation software offers a convenient and efficient way to not just present images, but also show them in close proximity to the related concept. This is exactly what psychologists believe is the most effective way to use images for instruction. Including images in a presentation also allows the instructor to make the microscopic world less abstract and more understandable to the students.
Some skeptics might argue that the textbook already provides enough images. Modern texts do, indeed, use a much more visual approach than has been the case in the past, but it is not clear that even the best-planned textbook can force (or even encourage) students to access the image at the most appropriate time. Remember that Images are most effective when they are close to the concept (or text) in both time and space. Many students are not accustomed to associating pictures in the text with the concept that they illustrate. And then, of course, there is the significant number of students who, for one reason or another, don't buy the textbook at all.
For convenience in surveying student responses, I have roughly classified chemical images into five categories: (1) molecular images, (2) diagrams of apparatus and equipment, (3) historical events, (4) industrial images, and (5) famous chemists. This set of categories seems to adequately represent the main types of images that are typically used, which, according to the students, have a different levels of usefulness.
The last two categories may present copyright concerns, depending on where they are obtained. Industrial pictures are useful, since many students may never have seen a major chemical plant. In general, my students report that pictures of famous chemists are less useful than other types of images. Thus, historical chemists seem to be more interesting to us than they are to our students. In some cases, however, a picture can suggest some personality trait that is relevant to the success (or failure) of the individual's work. For example, most photos of Mendeleev do indicate the strong personality who forced the chemical community to accept the periodic table. On the other hand, Avogadro's proposals were ignored for years, and his few existing images give little evidence of the forcefulness that is so clear in Mendeleev.
In anonymous surveys, my students have consistently reported
that the images made the notes more interesting, easier to understand,
and easier to remember. Images seem to accomplish everything that
the research promises and more. Several years ago, one of my students
made the following comment about the use of images in lecture
With the computer the concepts become real. They aren't just notes on a piece of paper. You actually prove that things happen and we just don't have to accept what you tell us.
It's hard to find a stronger endorsement of a teaching method than this.
Finding the best images and formatting them for a presentation does take time, but it is well worth the effort. Without images PowerPoint is just a very expensive overhead projector! If you are not willing to spend the required time, stick with the overhead; there are fewer technical problems.
1. Kleinman, R.W. et al, J.Chem.Ed. 1987, 64,
2. Johnstone, A.H. J.Comp.Assist.Learning, 1991, 75, 7.
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