Improving the Design of Laboratory Worksheets E. T. McDowell Rolle College, Exmouth, Devon, England R. E. L. Waddling Falmouth School, Falmouth, Cornwall, England It is unfortunate that laboratory sessions often are poorly used by both teachers and students. The demands of time, and nriorities of some examination boards. and the lack of aualhical thought by administrators (and some teachers), can lead to a clouding of the objectives of such laboratory work. Ittherefore seemsappropriate to reflect on the goals of such exercises and the resources utilitized during the laboratory session. I t is the intention of this paper 6 describe a technique to improve the adaptation, development, and utilization of laboratory worksheets. This may enable teachers to enhance their students' learning of the factual knowledge, through laboratory investigations, and also the manipulative skills being practiced. Althoueh manv have criticized the cookbook nature of 1aboratoG manuals, Johnstone1 suggests that such comments mav be an indictment of the form of the manuals utilized rather than a criticism of the student. The guidelines proposed in this paper have been empirically derived over a period during which they were repeatedly tested and modified. Students were closely monitored during the laboratory sessions and their report forms continuously evaluated to ensure the reliability and effectiveness of the proposedtechniques. Much of the work was done in an effort to compile a resource pack for secondary school teache r ~ . ~ Why A Laboratory Worksheet? It is our view that a laboratory worksheet should enable the student to work a t his or her own pace and he largely independent of the teacher. This frees the teacher to spend more time with those students who need extra attention. While the style and approach of worksheets can vary enormously from a problem-solving approach to a mundane following of a recipe, they all require the student to comprehend instructions, remember what to do, and then to execute a task. I t is by examining the three stages in this model that we can begin to see how laboratory worksheets can be made more effective. Key Aspects There is an increasing realization of the importance of pictures and diaarams in textbooks eweciallv when new information is being presented or unfamiiiar procedures and apparatus are being introduced. Such illustrations appear to give distinctive clues to the readers. This text-picture combination gives a richer representation of the subject material than does the use of text a l ~ n e . ~ . ~ The representation of experimental procedures in the dual mode of text and pictorial flow charts can greatly enhance the students understanding of the experimental procedures. In this way students are motivated t o compare the information presented in both the text and pictures. This process leads to rehearsal looping, a subconscious search for contradictions between the pictorial and written input. A continual looping of checks and balances is provided, and thus a deeper mental level of information processing is possible.3 Thus, we consider such a dual approach to be helpful in maximizing student understanding. Textual materials must be clear and concise. A student's
working memory can easily be overloaded. This is often due to the student's inability t o discriminate between those pieces of information that are vital and those that are peripheral to the e x e ~ c i s eIt . ~is therefore important that the writing be done in an imperative and commanding style. Sentences should be kept short. Frequent use of polysyllabic words, subphrases, and pronouns should be avoided. Use of synonymous or closely related terms within the same sentence can be very confusing to the novice and should be avoided if possible; e.g., "Put the filter paper into the funnel, and use the filtration apparatus t o . . . ." Experimental procedures should he sequenced into numbered steps. It is vital that each step be concise and specific so that it can be easily understood and remembered by the students while they carry out the manipulation. Embedding background information, explanations, and reasons for performing a particular task within a procedural detail can quickly overload the student. I t is recommended that such matters be made during follow-up questions or discussions. Similarly, avoid asking students to recall specific details performed in previous experiments, especially if the time lapse between the activities has been great or if the detail was of secondary importance. Diagrams should also be clear and uncluttered. Black line drawines that oarallel the sequence outlined in the text presents clear flow chart that enables the students to combine written instructions with pictorial representations in an efficient manner. The use of a series of pictures can greatly reduce the amount of text and can convey a far clearer idea of the nrocedures to he followed. The worksheets then become accessible to the students of a wide range of abilities. Once a task has been performed, the student must find his way back to the appropriate place on the worksheet in order to read the next set of instructions. We have found that students greatly prefer the use of numbered steps, the numbers actine as flaes. A text-onlv set of instructions, divided can be very diicouraging to students. Withinto out the use of numbered steps, students have to store unnecessary information, such as the shape and pattern of paragraphs. Other Factors So far we have discussed onlv techniaues for imnrovine ~ is t h i the comprehensibility of a worksheet. A I important style of the approach that is adopted. Laboratory exercises should involve genuine investigations in which the students are encouraged to attempt to solve problems. There is little educational value in using laboratory classes only to confirm the theorv that has been taught earlier in the course. Students should he placed in a problem-solving situation where 'Johnstone, A. H., Chem. Soc. Rev., 9,365 (1980). McDoweII. E. T., and Waddling. R. E. L.. "Chemistry Practicals." Addison Wesley. Reading, MA, 1984. Reid. D. J.. Briggs, N.. and Beveridge, M., Brit J. Educ. Psychol.. 53, 327 (1983).
'Jenkins. J. R., Neale. D. C., and Deno. S. L., Brit. J. Educ. Psychoi., 58,303 (1967). Johnstone, A. H., J. CHEM. EDUC.,61, 047 (1984). Volume 62 Number 11 November 1985
1037
Decomposing ethanol
How does the solubility of potassium chloride vary with temperature?
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QUESTIONS
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Figure 1. Sample worksheet on decomposition of ethanol.
Flgure 2. Sample worksheet on salubillty of potassium chloride.
they can immediately perceive the problem heing presented. If the worksheet is to meet these requirements, it must he able to convey unambiguously to the student the spirit of the investigation, as well as the procedures and necessary safety precautions. Techniques for promoting student interest and general examples of good practice are:
a1 looping. The introduction and title are placed above the apparatus and chemicals list. We have found that hazard symbols can be usefully placed a t the top of the page. We use symbolic representation for the hazards likely to be encountered. Any set of symbols could, of course, be used as long as their meanings areohvious to the student. At the end of each investigation sheet we have included a set of graded questions to enable the students to draw out the underlying . . principles. In the experiment on " ~ e c o m p o s i n g ~ t h a n o l(Fig. " 1)we have adopted a very obvious problem-solving approach. The design of the sheet enables the student to see a t a glance not only whatthe problem is but also the procedures that have to be executed in order to find an answer. In the case of the determination of the solubility of potassium chloride (Fig. 21, the value of a parallel set of diagrams is even more apparent. The idea of adding the solid until a saturated solution is obtained is reinforced by a repeat loop in the flow chart.
Choose an attractive title-usually posing a question or issuing a challenge. 2) Include a short introductory section defining the problem or explaining the tasks involved. 3) Present students with a well-organized and attractive worksheet. 4) Divide the experiment into a series of numbered steps. 5 ) Use a series of diagrams to complement or replace textual descriptions of manipulative tasks. 6) Usesafety symbolson the handout toalert studentstopwsible hazards. 7) Include lists of both apparatus and chemicals. 8) Adapt a standard format for each worksheet. 1)
Examples
Two examples of this new style of laboratory worksheet are shown in Figures 1and 2. A consistent format isused, the text beine". olaced on the left side of the Dane . and the flow charts on the right. These two parallel columns give a sense of progression through the experiment and promote rehears1038
Journal of Chemical Education
Student Writlng
I t is important that students should keep a meaningful record of their laboratory work. Effective writing requires the student to reconstruct the knowledge for himself. Reformulation by the learner increases the ease of recall of the knowledge, makes links with the other areas of knowledge v knowlmore obvious, and enables the learner to a ~ d the edge easily in new situations. This new st& of laboratory worksheet stimulates students to write in a creative manner.
