69 Research in Science Education, 1984, 14, 69-77 DISPLACEMENT OF WATER: WEIGHT OR VOLUME? A N E X A M I N A T I O N OF TWO C O N F L I C T BASED TEACHING STRATEGIES Chris Dawson and Jack Rowell In earlier work (Rowell & Dawson~ 1979~ I981~ 1983) we have attempted to develop the Piagetian notion of equilibration as a basis for teaching strategies designed to change students' ideas about various scientific problems. Like others we have utilised methodologies which have sought to encourage students to confront their beliefs with reality and with other beliefs~ and to evaluate the relationships between these. Both confirmation and c o n f l i c t have resulted from these evaluations~ but i t has generally been anticipated that resolution of c o n f l i c t would be of particular importance in stimulating concept development. Like others we have met with some, but always limited, success with these methods. Approaches to conflict based teaching falsificationist's view of progress in science. have tended to parallel the A scientific theory is falsified, and hence rejected~ if i t does not f i t the empirical evidence. However this view of science has its critics and Lakatos (1974~ p. l l9) suggests that '... there is no falsification before the emergence of a better theory'. Rowell (1983~ p. 70) has also argued that~ for the individual, equilibration operates '... to gain maximum power over the environment whilst conserving as much as possible of what is already known about it'. Here are suggestions then that i t may not be easy to change a student's ideas about the world simply by bringing them into continuing c o n f l i c t with other views or with reality; and this is in fact what has been observed in many studies. Instead there seem to be sound theoretical reasons for attempting to provide students with a more powerful explanatory idea than they already have before they are asked to compare the two. Within such a strategyy conflict would~ instead of being a continual process~ be delayed u n t i l the intended replacement is well understood. 70 In this study, two short c o n f l i c t based teaching methods were developed to attempt to help students understand that the volume of an immersed object, rather than its weight, is the sole factor which determines the water level rise caused by its immersion. One method utilised an orthodox conflict (OC) approach, the other a framework replacement (FR) strategy. The content of the teaching sequence was chosen for two reasons. Firstly, in previous studies we have found that a considerable proportion of Year 9 students gave weight based arguments in explanation of various problem situations involving water displacement, and i t was expected that the proportion would be higher still for Year 8 students, the target group of this study. Secondly, i t was believed that in this content area we have a clear example of two 'alternative frameworks' (Driver & Easley, L978). An 'alternative framework' is characterised by a degree of homogeneity in the way in which a range of problem situations is interpreted. However the term is used loosely and a comment made by F]avell about Piaget's schemes might be borrowed; alternative frameworks '... seem to come in ell shapes and sizes' (Flavell, 1963, p. 54). What provides evidence of an alternative framework is consistency of explanatory response, but the range of content where consistency must be shown to count as evidence of an alternative framework, end not simply a minor misconception, needs to be identified by the researcher in each case. In the case of water displecement two major 'frameworks' can be anticipated; one where a student consistently uses weight explanations to justify made predictions about water displacement, end one where volume explanations are used. [n this study consistency is defined w i t h i n responses which relate to three problematic aspects of displacement volume which are discussed later. METHOD Design A pre-test, post-test, delayed post-test controlled experimental design was used, with four weeks separating the post-tests. One of three equivalent mixed ability classes in a South Australian high school was designated the control group, one was taught by the OC method and one by the FR method. Teaching was completed in two separate f i f t y - m i n u t e lessons (both classes were taught by one of the researchers (C.D.)) end was followed in the next class lesson by the post-test. The same test instrument was used for all tests. Test Instrument The test incorporated the Piagetian conservation tasks which utilise two plasticlne balls to stimulate students' prediction and explanation of the effect of 71 shape change on weight, volume, and displacement volume (Rowell & Dawson, 1983). To this test additional questions were appended which looked more closely at students' understanding o f water displacement. Specifically three d i f f e r e n t aspects of water displacement were examined. 1 One of two balls of plasticine which had been adjusted to be of equal weight was squeezed into a sausage shape. Students were asked to say whether the water level rise produced by the ball and the sausage would be the same or different and were asked to give an explanation for the prediction. 2 Students were asked about the relationship of the volume of water displaced (as measured by water level rise) to the volume of the immersed object. They were asked whether the two were the same, or whether one was greater, and to explain their answers. 3 From one of two equal balls of plasticine a small piece was removed and replaced by an equal volume of lead. Students were shown that the two had very ~different weights but the same volume. They were then asked to predict whether the water level rise produced by the two balls would be the same or different, and to give an explanation. Students operating an alternative framework utilising weight as the cause of water displacement were expected to give weight explanations (and not volume) in 1 and 3, and possibly in 2, though this was unlikely as the question asked specifically about volume. Students with a volume explanatory framework should give explanations based on volume to all three. Teachin 9 Usin 9 the Ordinary C o n f l i c t Method (OC) Students were first reminded about weighing objects and the units of weight. Four objects (blue, red, and yellow cubes and a stone) were each weighed with the help of a student assistant, and the results recorded on the chalkboard. Two of the cubes (blue, yellow) had the same weight but very different volumes, two cubes (blue, red) had similar volumes but different weights. lightest to heaviest. Students then listed the objects A similar procedure was adopted to list the same objects in order of volume, volumes of the cubes being calculated and that of the stone being given. Students were then asked to predict the relative rise of water level produced by the objects on immersion. It was suggested that i f they wished they might look back at the weight and volume orders. Some students then gave their suggestions and reasons; only weight and volume ordering emerged. Students were asked to note the differences in the orders, and asked how many had picked each one. lesson 1. This ended 72 [n lesson 2 the previous lesson was summarised and students referred back to their predictions of water level rise. The experiment was not done with the water rises being recorded, and students being asked to order them from smallest to greatest. They were also asked to privately compare this with their own predictions. If wrong they were to compare the water level rise table with the weight and volume tabulations to see i f either of these better predicted the water rise. Following this a lump of plasticine was introduced. It was weighed and students recorded this and wrote a new order of weights for the 5 objects. Its volume was calculated after pressing i t into a cube and it was placed into a new order of volume. Students then individually predicted the new order of water level rise for the five objects and gave explanations for recorded and discussed. their predictions. Some of these were The water level rise produced by the plasticine was measured and the result compared with the predictions. Finally the series of experiments was discussed and summarised. Teachin 9 Usin 9 the Framework Replacement Method (FR) While this method provided identical experiences for the students, the order of presentation differed, reflecting a five-step strategy (Rowell & Dawson, 1983, p. 214). (a) Students were made consciously aware of their existing ideas. Firstly, students were asked to consider the water level rise produced by an immersed object and to suggest what features of the object might be important in determining the amount of the rise. They were asked to record their thoughts individually. (b) D i f f e r e n t ideas were not discussed in detail or brought into c o n f l i c t but accepted as equally possible solutions. (c) Students were asked to retain their ideas, but were told that one possibility would be taught, and that their help would be needed later for its evaluation. Students were informed that we were going to look closely at one of these explanation~ that of the volume of the object, We were not saying i t was an important factor but we were going to look at some experiments assuming that volume was i m p o r t a n t . Later they would be asked to look at this view and compare i t with reality and their original view. 73 (d) The idea was taught linking it, where possible, to existing knowledge. First students recorded the volumes of the four objects, and ordered them from smallest to largest. They were then asked to predict the relative water level rises produced assuming that volume was important. The experiment was done and the results compared with the predictions. Now the plasticine was introduced, its volume given, predictions about the water level rise made~ and the empirical results compared with the predictions. By now it was agreed that the volume of the object was a good predictor of water level rise. (e) Once students would use the new idea, the old ideas were recalled for comparison and both are compared with reality. A t this point, we returned to the alternative explanation that many students had given, that of weight. The four objects were weighed and ordered from [ightest to heaviest. A comparison of this list with the water level rise table showed that the orders were different. The plasticine was now introduced~ and again i t was found that its weight was not a good p r e d i c t o r of the w a t e r l ev el rise it produced. Finally the series of e x p e r i m e n t s was discussed and summarised. RESULTS Responses by all students (control plus experimental) to the pre-test questions showed that~ as expected, a considerable proportion (43/69) gave some weight-based explanations for predictions made. However~ the degree of consistency in the use of weight arguments was low and only ]3/69 gave f i r m evidence of a consistently weight-based 'alternative framework I. In the delayed post-test nine students utilised a weight-framework (seven of these did not do so on the pre-test) and 25 a volume-framework. A l l ten students giving evidence of a volume-framework on the pre-test retained that on the delayed post-test. In view of the purpose of the experiment9 to investigate framework replacement9 it was important to follow the progress of the weight-framework. 13 students who began with a Three were in the OC groupy eight in the FR group, and two in the control group. Three of these students (one OC7 two FR) showed evidence of a total framework replacement~ giving consistent volume explanations in the delayed post-test. change. Two students (one control (no delayed post-test)9 one FR) showed no All t h e others showed less structurally organised responses with combination of weight and volume explanations, or uninterpretable in these terms. a 74 What is evident in these results is that, though some students did operate a consistent framework, and though rapid framework replacement did take place, neither was very common. More commonly, lack of consistency and slow changes in understanding were observed and it is this aspect of the results which is illustrated in Figure 1 where the progress of all students who gave a weight explanation in the weighted ball question on the pro-test is followed (though other groups could have been selected to show similar patterns of progress). In Figure I an operative weight framework takes the form WWW or W-W and a volume framework VVV. DISCUSSION This study had the particular aim of using conflict methods to e f f e c t total framework replacement. While this did happen (three cases in Figure 1), such a change following this short intervention was infrequent. A major factor to consider here is that very few students ( l I in the experimental groups) gave evidence of a consistently operative weight framework at the start of the experiment, hence the number of 'potential customers' was few (this was disappointing in view of earlier work with Year 9 students). Nevertheless, the teaching methods adopted here had no striking effect on these students, and progress was characterized more by gradually increasing understanding than by rapid framework displacement. Further, despite the focus of the teaching sequence being on one particular aspect of displacement - that of the possible relationship of the attributes of the object (weight and volume) to the water displaced, understanding of other aspects of displacement volume were just as likely to be the first to show a volume explanation: there was no evidence at all that students were giving verbally learned answers to the weighted ball question. As the focus of the teaching sequence had been solely on this particular aspect, it was i n i t i a l l y hypothesised that its understanding might be transferred to other aspects, thereby allowing the student to rapidly generate a volume-framework. That the teaching led to unpredictable progress in any of the three aspects of displacement volume tested indicates that experiences which we deemed c r i t i c a l for understanding one of them may instead have assisted some students to understand other aspects. There was no one-to-one relationship between what was taught and what students learned. As discussed earlier, the term 'alternative framework' has been used widely, though often without a specific definition of what is to be understood by this when applied to a particular content area. For Year8 students Walternative framework' seems to imply a far greater degree of consistency than is apparent for most students at least in this content area. FIGURE ! 3 volume explanations 2 volume explanations I volume explanations 0 volume explanations PROGRESS STUDENTS PRETEST V v - W - W A TO DISPLACENENT WEIGHT EXPLANATION OF Post test VVV - W W---~- - W W Pre test tVVV Delayed post test Ordinary c o n f l i c t (N = 7) THREE " ASPECTS GIVING ON V2 Delayed post test ~..-' v ~ a b s VI- ~ V Post test Control (N = 10) OF Pre test / ~ w w wk~---~ abs (3~ aDS , / / "p.~ % W W ~ - W W--~ - w -~'~ - 1. relationship of volume of water displaced to object volume. equality/inequality of water displacement by sausageand b a l l . WEIGHTED BALL VOLUME* - PROBLEM ~ IN Delayed post test - v V V V /t W W - W / v ~w/---~ ~ v w // vw / v w/~///v-w Post test Framework replacement (N : I0) Pre test / vww W W - - _W ~ W ~ _ W W The three records for each student show the type of explanation for each of the three aspects of displacement volume. 2. - = no explanation or other. volume displaced by weighted and unweighted balls. V = volume explanation 3. W = weight explanation 76 A further aim of this study was to investigate the relative effects of two different c o n f l i c t methods. Because of the small numbers involved in making any particular change this is d i f f i c u l t to do, but in general terms i t appears that the methods were about equally e f f e c t i v e . However two possible differences were noted. Initially several students who conserved weight but not internal volume (comparison of the volumes of a plasticine ball and a sausage made from a similar ball) also conserved displacement volume, reasoning that because the sausage and the ball had similar weights, they would create the same water level rise. However on the post-test and/or delayed post-test, the fact that i t is the volume of an object which determines the amount of water displaced was recognised and was integrated with the failure to conserve internal Volume. Hence students responded that the water level rise caused by the ball and sausage would be different as the two had different volumes. Interestingly, of the students who potentially could show this change (i.e., i n i t i a l l y failed to conserve internal volume and gave a weight explanation for equality of displacement by sausage and ball) 1/7 of the OC group and 7/1) of the FR group actually showed it, suggesting that perhaps the l a t t e r method was rather more effective in promoting such logical interrelated understanding. A further small difference in results is shown in Figure 1. Between post-test to delayed post-test, 2/7 students in the OC group showed an increase in the number of volume answers given, and two also showed a decrease. In the FR group however, 5/10 students showed an increase in the number of volume explanations whereas no student showed a decrease. An earlier study on teaching control of variables by the two methods used here, (Rowel! & Dawson, 1984) showed somewhat similar results with stability and even improvement of framework application between post- and delayed post-tests being more in evidence in the FR group. Ira_plications for Teachin 9 and Research Watts (1983) has stated that Poy better understanding the beliefs and commitments of pupils about the concept of forcer the teacher has a firmer basis from which commitments to choose particular teaching approaches'. are held by individuals not class group= But such beliefs and as Watts (1983) said 'a framework is a composite picture based on ideas shared by a number of pupils'. Such artefactual structures are no basis on which to develop c o n f l i c t related teaching strategies; strategies which, with the concept of equilibration at their core, must focus on individual learners. Rather the teacher would need to identify individual understandings and devise individualised sets of learning experiences designed to provoke conflict for each student - a major, i f not impossible9 task. 77 The FR strategy recognizes this dilemma. Its concern is to provide each individual in the group with the same coherent well understood framework which is in potential conflict with any and all of their individual, idiosyncratic, relevant prior conceptions, individual problems are then resolvable by individuals. What teachers must attempt is to raise as many as they can, to stimulate students to do the same, and to require solutions and explanations. As may be seen the FR strategy differs l i t t l e from normal good teaching approaches except at the very beginning and at the very end. REFERENCES DRIVER, R. & 3. EASLEY. Pupils and Paridigm~ A review of the literature related to concept level in adolescent science students. Studies in Science Education, 1978, 5, 61-84. FLAVELL, 3.H. The Developmental Psycholoy Educational Publishing, 1963. of 3ean Piaet. New York, Litton LAKATOS, I . Falsification and the methodology of scientific research programmes. [n Lakatos, I. and Musgrave, A. (eds) Criticism and the 9rewth of knowledge. London, Cambridge University Press, 1974. ROWELL, 3.A. Equilibration: Developing the hard core of the Piagetian research program. Human Development, 1983, 2--6961-71. ROWELL, 3.A. & DAWSON, C.3. Cognitive conflict: Its nature and use in the teaching of science. Research in Science Education, 1979, 9_, 169-75. ROWELL, 3.A. & DAWSON 9 C.3. Volume, conservation and instruction: A classroom based Solomon four group study of conflict. 3ournal of Research in Science Teaching, 1981, 188, 533-46. R O W E L L , 3.A. & D A W S O N , C.3. Laboratory counterexamples arld the growth of understanding in science. European Journal of Science Education, 1983~ 5, 203-15. ROWELL, 3.A. & DAWSON, C.3. Controlling variables Testing a program for teaching a general solution strategy. Research in Science and Technological Education, 1984 (in press). WATTS, D.M. A study of school children's alternative frameworks of the concept of force. Studies in Science Education, 1983, 5_9217-30.