R. Ben-Zvi, A. Hofstein, D. Samuel Science Teaching Department Weizmann Institute of Science Rehovot, Israel and R. F. Kempa University of Keele Staffordshire.England
II
The Effectiveness of Filmed Experiments in High School Chemical Education
I
Educationists and scientists concerned with science education issues have repeatedly stressed the importance of laboratory work not only as a means of leading the science student to a deeper understanding of the discipline studied by him hut also in order to convey to him the spirit of scientific enquiry and the essence of scientific thinking (1-3). Accepting this view, the developers of modern chemistry curricula have invariablv. eiven laboratorv work a nrominent d a c e in the .. student's overall chemtral education activities. Thts applies to cllrricula develo~rdin the States as well as to those developed elsewhere. However desirable in educational terms the a d a ~ t a t i o nof a laboratory-based approach to chemical education may he, there are instances when its implementation at the high school level presents difficulties. For example, schools may lack the economic means of providing adequate facilities, equipment, and materials for the conduct of extensive laboratory work. Or there may be administrative problems, such as the nonavailability of laboratory space at the "right time," which make it difficult to integrate fully laboratory work with other chemical education activities to which the learner is exposed. Recognizing the prohlems which may hinder the implementation of an extensively lahoratory-based approach to chemical education a t the high school level, we have recently conducted a studv of the effectiveness of filmed exneriments as an alternative to normal student-centered laboratory work. The studv was undertaken in coniunctiou with the develonment of a new chemistry curriculum aimed a t the senior high school level in Israel (Grades 10-12). (.4.) . This new curriculum itself is extensively laboratory-oriented in that it prescribes manv experiments to he carried out hv students in an integrated way with other learning experiences in chemistry. Although most schools in Israel are sufficiently well equipped to be able to adopt the new curriculum, a number of institutions have so far not managed to implement it fully because of the type of problems outlined above. For these, substitution of student experiments by filmed experiments was thought to constitute viable eduiational alternative. The potential advantages of film and related media in the teaching of chemistry have been extensively discussed in the literature (5, 6); yet, few evaluations of the educational ef-
.
a
518 / Journal of Chemical Education
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~ o t ~student ll sample (130 boys and 200 girls, loth Grade, aged 15 years) Division
into two groups of similar abilities
'Film Group'$.N = 150) E x p o e r e to rlmed
'Experiments Group' (N = 180) Students performed own experiments
erpenments place of own expenmentation
t
Post-InsVuetion Testing (tests identified in text) The experimental shatagy (schematic)
fectiveness of these media have so far been conducted. One investigation recently reported (7)demonstrated the usefulness of video-recorded demonstration in the acquisition of manipulative skills and suggested to the present investigators that film may be an effective medium for the teaching of manipulative skills even when laboratory facilities for "personal practice" are not readily available. In the study reported here, the comparative effectiveness of filmed experiments and personalized laboratory experiences was examined in relation to the following 1) General
achievement in chemistry (knowledge and understandine of subiect matter). 2, Knowledge of pr~nrrplesunderlying chemical experiments and Inhoratury techniques. 3) hlnnipulative sk~llsrelating to the handling ofequrpmenr and the use of apparatus. 4) Observational attainment and problem-solving abilities in relation to laboratory situations.
The Research Strategy
The strategy chosen for the investigation is summarized in the figure. T h e total population consisted of 330 10th grade students (130 males, 200 females) drawn from six different high schools. All students were in their first year of chemical studies, although they had previously studied both physics and biology. The students were divided into two groups, a "film-group" ( N = 150) and an "experiments-group" ( N = 180). A number of pretests were carried out, including astandardized IQ test and a Science Interest and Attitudes test (a), to establish the equivalence of the two groups with respect t o these characteristics. Differences between mean scores on these measures were very small and statistically insignificant. The two groups were subjected over a period of five months to identical learning experiences in chemistry except that one group undertook practical work a t the prescribed times whereas the other observed "filmed experiments." Altogether 11key experiments were covered in this differential way, relating to the themes, "mass and volume relationships in chemistry" (4 experiments), "oxidation and reduction" (5 experiments), and "atomic structure': (2 experiments). The filmed experiments were presented as 4-min silent film loops in color with Hebrew captions, and portrayed the exTable 1.
A Breakdown Analysis of Manipulative Skills
Skill Components
Generalized Arresrmenf CriteriaIPerformance Features
Experimental Technioue
Correct handlins o f aDDaratur and
results. Cowed sequencing of tarkr forming part of a n overall operation; effective and purposeful utiiiza tion of equipment. fficient use of working time; & l i t y to develop an acceptable working procedure on the barir of limited instructions. Swift and confident manner of execution of practical task% IUCCBIIfUI completion of an Operation or its constituent
Procedure
Manual Dexterity
periments in a way similar 10 that encountered by students in the experiments-group. Follow-up work to the experiments or simulated experiments was identical for both Altogether five different tests were developed to assess the comparative effectiveness of personalized laboratory work and of filmed experiments 1) Achieuement in Chemistry Test (AC). This was a %-item
multiple choice test examining general knowledge and the understanding of various facts and principles covered in the chemistry course to which students had been exposed during the investigation. The test had an average difficulty index of 0.61 and a Kuder-Richardson reliability of r = 0.78. 2) Specific Knowledge Test (SKI.' This was designed to assess students' knowledge and understanding of the use of experimental techniques and of the principles underlying laboratory work and procedures. The test was divided into two sections, A and B, dealing with Principles and Techniques/Methodalogy, respectively. 3) Practical Test 1 (PT 1 ) . This was a practical test requiring students to perform experimental work according to well.de. fined instructions;its chief purpose was to examine the manipulative skills of the experiments-group following previous training in similar experiments,and of the film-groupwho had only had indirect experiences of the same experiments. The actual assessment of the students' performances on this test was made by reference to an assessment check-list of the type suggested elsewhere (7, 9). The individual performancecriteria laid down in the check-list embraced four subcategories of manipulative skills previously suggested by one of the authors ( 9 ) , and identified in Table 1. 4) Practical Test 2 ( P T 2 ) .This was developed in order to examine students' skills in the context of a problem-solving situation involving not only manipulation to be performed but also the planning of an experimental praeedure in an area not previously encountered by students. The exercise chosen for this purpose was the quantitative investigation of the effects of heat on cadmium carbonate. The assessment was carried out using a suitable checklist, as for practical test 1. 5) Obseruotion Test (0.T).This consisted of six test-tubereactions covering the followingpereptual areas:color changes, evolution of rases. tem~eraturechanees. and the orecioitation of solids.
..~
DlltC
Orderlinerr
Tidiness of the worYing area: good utilization of available bench-space; puvpoleful plating of apparatus and equipment~
Table 2.
Variable
(10)).
Means and Standard Deviation1s of the Overall Scorer on tha Tert Battery score Rsnw
Variable
Table 3.
'The tests listed under 2 to 5 were designed as criterion-referenced tests. A statement of the usual test statistics is inappropriate (Ref.
Film-Group Mean SD
ExperimensGroup Mean SD
Significance t-value
Level
Means and Standard Deviations for the Sub-Sections of the Practical Terts
Score Scale Range
Film-Group Mean S.D.
Experimens-Group S.D.
Mean
f-value
Significance Le"ei
1
Practical Tert 1 E x P ~Technique . Procedure Manual Dexterity Orderlinerr Practical Tert 2 Expt. Technique Procedure Manual Dexterity Orderlinerr Oblervation Tert Color Change$ Non-color changer
Volume 53.Number 8, August 1976 / 519
tions made. Separatescores were obtained for the mlor and the non-color changes, respectively. Results and Discussion Table 29hows the mean scores and standard deviations obtained by the two groups on the various post-tests, together with the results of t-tests on these data. The general picture is that the performance of the two groups is remarkably similar. No significant differences appear in relation t o the cognitive measures used and to the observation test and the practical situation involving the problem-solving task. Only with respect to the practical test assessing predominantly students' manipulative abilities did the experiments-group out-perform the film-group, but even in this respect is the performance advantage of the former over the latter a mere 10%. This initial analysis suggests vicarious experience of experimental work, provided by means of filmed experiments, to be no less effective educationally than direct laboratory experience gained bv students, ignoring the one area where lat;oratory work may be argued to convey specific training: manipulative skills. This aspect is brought out more clearly by a consideration of the mean performances of the two groups in relation to the constituent components of the manipulative skills domain, as identified in Table 1.InTable 3, comparison is made of component mean scores on the laboratory tests for the two groups. Data for the performance of the groups in the observational test are also included. It is seen that where differences between the two moups are found, these relate t o the first practical test and the observation test. As has been pointed out, the f i t practical test ( P T 1) examined manipulative skills acquired by students in connection with experimental work which had previously heen experienced by them, either directly or vicariously, as part of their chemistry curriculum. The test was therefore measuring what, in analogy with the cognitive domain, may be described as "recallable" skills. In this situation, the superiority of personalized laboratory work is clearly demonstrated: it affects students' competence in the handling of equipment, the seauencine and the wav in which tbev -of o~erations. . " organize their equipment and working area. The mean score difference for the "manual dexteritv" comoonent is too small to reach an acceptable ~ t a t i s t i c a l ~ i ~ n i f i c level, ~ n c e but again shows some slight superioritv of the experiments-group. .. . For ihc second practical test, all mean score differences for the components of "manipulative skills" fail to be statistically
520 / Journal of Chemical Education
significant; neither do they indicate any uniform trend in favor of one or the other group. This practical test was, of course, less concerned with the examination of "routine" skills. hutinstead-required students to adapt and transfer their pr&tical abilities to a new exwrimental situation. It would aowar .. that previous direct training in special procedures, as experienced by the experiments-group, does not result in a distinct advantage in this new test. The slightlv suwrior wrformance of the f h - m o u o on color observatibns-is intereiing inasmuch as it maiweli point to an enhancement of students' color wrception as the result of the portrayal of color changes by film. For the non-color changes incorporated in the observation test, the reverse phenomenon is found, but only in a minor way. Conclusions The study was carried out in order to examine the educational effectiveness of filmed experiments in high school chemical education, compared with that of normaipersonal experience of practical work. The results indicate that, excepting the manipulative skills area, film-loops showing experimental situations are an effective substitute for students' individual laboratory work in that they do not affect adversely cognitive or laboratory-based nroblem-solvine achievement. In the area of routine manipulative skills, direct experience of laboratory work obviously leads to a higher performance level; but the relative advantage gained by experiments-group students over film-group students is small and points strongly to the potential of filmed experiments as a means of teaching manipulative skills. In the light of the present study, the conclusion is justified that well-designed films or film-loops are a viable alternative to student-based laboratory work, especially in situations where as the result of ad&nistritive, economic, or time problems, a truly laboratory-oriented approach to chemical education is not readily implemented. Literature Cited (1) Bruner. J. S.,HaruordEduc.Rou., 31.21 (1961). 12) Campbell. J.A.. J.CHEM.EDUC.,38.2 (1961). la) schwah. J. J., in schwah, J. J., and ~ ~ ~P. E.,~- ~d hi^^ h ~~ of ~ science," i ~ , Harvard University PIPSS. Cambridge, Mass.. 1961, pp. 1-103. (41 "Chemistry for Hieh School."Vok. 1-3. WeivnannInrtitutedSeiena. RehoW.larae1
1972-74 lm ~ebreu). i5) Brubaker, C. H..Sehwendeman, R. H., and McQuarrie, D. A,, J. CHEM. EDUC.,41,
(10) Popham. J. W..and Huaek. T.R,J . Educ. Mooruremonf, 6.111969).
