The conceptual change approach to teaching chemical equilibrium

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The conceptual change approach toteaching chemical equilibriumNurtaç Canpolat a , Tacettin Pınarbaşı a , Samih Bayrakçeken a &

Omer Geban ba Atatürk University, Turkeyb Middle East Technical University, TurkeyPublished online: 19 Aug 2006.

To cite this article: Nurtaç Canpolat , Tacettin Pınarbaşı , Samih Bayrakçeken & Omer Geban(2006) The conceptual change approach to teaching chemical equilibrium, Research in Science &Technological Education, 24:2, 217-235, DOI: 10.1080/02635140600811619

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Research in Science & Technological EducationVol. 24, No. 2, November 2006, pp. 217–235

ISSN 0263-5143 (print)/ISSN 1470-1138 (online)/06/020217–19© 2006 Taylor & Francis DOI: 10.1080/02635140600811619

The conceptual change approach to teaching chemical equilibriumNurtaç Canpolata*, Tacettin Pınarba[scedil] ıa, Samih Bayrakçekena and Omer GebanbaAtatürk University, Turkey; bMiddle East Technical University, TurkeyTaylor and Francis LtdCRST_A_181103.sgm10.1080/02635140600811619Research in Science & Technological Education0263-5143 (print)/1470-1138 (online)Original Article2006Taylor & Francis242000000November 2006Nurtaç[email protected]

This study investigates the effect of a conceptual change approach over traditional instruction onstudents’ understanding of chemical equilibrium concepts (e.g. dynamic nature of equilibrium,definition of equilibrium constant, heterogeneous equilibrium, qualitative interpreting of equilib-rium constant, changing the reaction conditions). This study consisted of 85 undergraduatestudents from two classes enrolled on an introductory chemistry course. One of the classes wasassigned randomly to the control group, and the other class was assigned randomly to the experi-mental group. During teaching of the topic of chemical equilibrium concepts in the chemistrycurriculum, the conceptual change approach was applied in the experimental group whereas ‘tradi-tional instruction’ was followed in the control group. The data were analyzed using analysis of cova-riance. The results showed that the students in the experimental group performed better comparedto the control group. The average percent of correct responses of the experimental group was 70%,and that of the control group was 51%, after treatment. In addition, it was found that students’science process skills made a statistically significant contribution to the variation in students’understanding of chemical equilibrium concepts.

Introduction

The existing knowledge of the learner plays an important role in the learning process.Often this knowledge comprises ideas which are not in agreement with those generallyaccepted by scientists and these have been variously termed ‘alternative conceptions’,‘alternative framework’ or ‘misconceptions’ (Garnett et al., 1995; Case & Fraser,1999; Sungur et al., 2001). Characteristics of misconceptions were summarized bySungur et al. (2001) as follows: they are resistant to change, persistent, wellembedded in an individual’s cognitive ecology and difficult to extinguish even withinstruction designed to address them. Since learning is the result of the interactionsbetween what the student is taught and his/her current ideas or conceptions,

*Corresponding author. Atatürk Üniversitesi K. K. E[gbreve] itim Fakültesi, Kimya E[gbreve] itimi A. B. D.,25240, Erzurum, Turkey. Email: [email protected]

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218 N. Canpolat et al.

misconceptions interfere with further learning. They make it difficult to see the ‘bigpicture’, to realize the links among science concepts and principles, and to apply theseprinciples meaningfully to daily life.

During instruction learners generate their own meaning based on their back-grounds, attitudes, abilities and experience. According to the cognitive model,students build sensible and coherent understandings of the events and phenomenain their world from their own point of view (Osborne & Wittrock, 1983). In the lastthree decades, a large body of research has described concepts held by sciencestudents at different levels. A considerable amount of research shows that relativelyyoung children develop intuitive ideas and beliefs about natural phenomena. Asthey learn more about the natural world they develop new and revised conceptsbased on their interpretation of this new information from the viewpoint of theirexisting ideas and beliefs. Their concepts are not consistent with the consensus ofthe scientific community. Some are on the right track but are incomplete and othersare simply wrong (Mulford & Robinson, 2002). Reviews of common alternativeconceptions of chemistry concepts and chemical behavior (Gabel & Bunce, 1994;Wandersee et al., 1994; Garnett et al., 1995) and an extensive bibliography (Pfund& Duit, 2000) are available. Research in this domain has attempted to answer ques-tions such as which misunderstandings occur, what are their origins, how extensiveare they and, of course, what can be done about them? (Gil-Perez & Carrascosa,1990). It is quite understandable why students’ ideas concerning chemical phenom-ena have become a research focus. Many students both at secondary level and atuniversity struggle to learn chemistry and many do not succeed. Research nowshows that many students do not understand fundamental concepts correctly andalso many of the scientifically incorrect ideas held by the students go unchangedfrom the early years of schooling to university, even up to adulthood (Nakhleh,1992). By not fully and appropriately understanding fundamental concepts, manystudents have trouble understanding the more advanced concepts that build onthem (Thomas, 1997).

For chemists the chemical equilibrium is fundamentally important and must beunderstood but many students find it a difficult concept so they have many miscon-ceptions about it. A large number of research studies in chemical education havefocused on students’ understanding of chemical equilibrium concepts. Thesestudies show that students have several misconceptions regarding chemical equilib-rium (e.g. Wheeler & Kass, 1978; Hackling & Garnett, 1985; Banerjee, 1991, 1995;Quilez-Pardo & Solaz-Portoles, 1995; Huddle & Pillay, 1996; Voska & Heikkinen,2000).

The content of science and the way that links between ideas are organized play animportant role in the learning process. The procedures used by the learner to repre-sent and organize knowledge and the learner’s epistemology and ability level are allcrucial factors that influence the manner in which students learn (Tyson et al., 1997).Since new knowledge is constructed on the base of existing cognitive structures,misconceptions have to be remedied in order to prevent a new one developing.However, students’ misconceptions could be so deeply rooted that traditional

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The conceptual change approach to teaching chemical equilibrium 219

instruction may be somewhat inadequate to change those concerning scientificconcepts (Wandersee et al., 1994; Cakir et al., 2002). Recent studies in science educa-tion showed that teaching strategies based on a conceptual change approach havebeen effective in dispelling students’ misconceptions (Hynd & Alvermann, 1986;Smith et al., 1993; Hynd et al., 1994; Hynd, 2001; Sungur et al., 2001).

The conceptual change approach to deal with students’ misconceptions has devel-oped over the past 20 years and is based on Piaget’s construct of disequilibrium andZeitgeist change or paradigm shift literature in the philosophy of science (Chambers& Andre, 1997). The conceptual change approach was developed by Posner et al.(1982) and Hewson (1981) and more recently, revised by Strike and Posner (1992).The conceptual change approach suggests that four conditions must exist before aconceptual change is likely to occur: students must become dissatisfied with theirexisting concepts; the new concept must be intelligible; the new concept must appearplausible; the new concept must be fruitful (Posner et al., 1982).

One instructional strategy based on the conceptual change model by Posner et al.(1982) involves the use of refutational texts or conceptual change texts described byHynd and Alvermann (1986), Alvermann and Hague (1989), Dole and Niederhauser(1990), Wang and Andre (1991), and Chambers and Andre (1997). These texts arethose that refute commonly held naive concepts and are designed to make readersaware of the inadequacy of their intuitive ideas, directly stating, through the use ofexplanations and examples, that commonly held intuitive ideas do not explain certainphenomena. In other terms, a conceptual change text introduces a common theory,belief or idea, refutes it and offers an alternative theory, belief or idea that is shown tobe more satisfactory (Hynd, 2001).

Literacy researchers, after years of studying conceptual change in science, havecome to one fairly stable conclusion: students change their intuitive but non-scientificconceptions to more scientific ones by reading conceptual change texts (Alvermann& Hague, 1989; Alverman & Hynd, 1989; Guzzetti et al., 1993, 1997; Hynd et al.,1994; Dole, 2000; Cakir, 2002). However, recent interviews with students haveshown that although conceptual change texts are generally effective for groups ofstudents, in some cases they will need to be implemented by discussion for some indi-viduals, particularly those with reading and writing difficulties (Guzzetti et al., 1995).Despite the ability of conceptual change texts to cause students cognitive conflict anddissatisfaction with their extant beliefs, cognitive conflict alone is not sufficient toproduce conceptual change (Guzzetti, 2000).

The recognition that science learning may require conceptual change on the partof the learner has generated a substantial amount of research aiming at the identifica-tion of: (1) students’ misconceptions of a variety of science topics; and (2) instruc-tional approaches that facilitate the restructuring of misconceptions (Diakidoy et al.,2003). Posner et al. (1982) presented the basic elements of a theory of conceptualchange and focused on radical conceptual change in which the Piagetian notion ofaccommodation in individuals was linked to Kuhn’s notion of revolutionary science.As stated before, for accommodation to take place, the authors suggested that newconceptions should be intelligible, plausible and fruitful and also proposed five kinds

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of concepts that determine the direction of an accommodation within a person’sconceptual ecology. Among these concepts, they presented analogies and metaphorsas having the potential to suggest new ideas and to make them intelligible. As explan-atory tools, analogies are particularly common in everyday speech and in the scienceclassroom because of their potential to compare one object or situation with anotherefficiently and, in the process, transfer either details or relational information or both(Treagust et al., 1996). Analogy mainly refers to comparisons of structures or rela-tions between two domains which involve the transfer of relational information froma domain that already exists in memory (source or base) to the domain to be explained(target). Analogy allows the application of pre-existing conceptual structures to newproblems and domains, and hence supports the rapid learning of new systems.Studies that examined analogies in relation to science learning have focused onwhether analogies enhance students’: (1) ability to solve problems; (2) understandingof text; (3) conceptual understanding of scientific content; and (4) construction ofscientific explanations (Dagher, 1994, 1995).

There is mounting evidence that analogies and models can play an important rolein facilitating student learning. In one of the studies examining the contribution ofanalogies to conceptual change, Zietsman and Hewson (1986) stated that analogiesproduced significant conceptual change in students holding alternative conceptions.Brown and Clement (1989) reported that analogies appeared to help enrich students’conceptions of target situations. In another study, Dupin and Joshua (1989)concluded that there was a clear difference between the experimental group in whicha mechanical analogy was presented and the control group with no analogy. Stavy(1991) studied analogical transfer in second, third and fourth grade children andshowed that the performance of the experimental group was significantly higher thanthe control group after instruction. Oliveira and Cachapuz (1992) described ninth-graders’ understanding of elementary atomic structure as deduced from thecommonly used analogy between the planetary system and the Bohr Model. Theyoffered the approach as one way of exploring metaphorical language interactively inorder to help students to analyze and evaluate their own knowledge. Treagust et al.(1996) assessed the efficacy of using analogies to engender conceptual change instudents’ science learning about the reflection of light and their findings illustratedthe utility of an analogical teaching approach for engendering conceptual change.Fast (1999) showed that analogies can be effective in producing a desired conceptualchange in high school students’ probability concepts.

Generally, a new conception is unlikely to displace an old one unless the old oneencounters difficulties, and a new intelligible and initially plausible conception isavailable that resolves these difficulties. That is, the individual must first view anexisting conception with some dissatisfaction before he/she will seriously consider anew one (Posner et al., 1982). Only interactions that promote a dialogue between thelearner’s existing conceptual understanding and accepted scientific understandingcan facilitate the construction of new personal meanings from pre-existing ideas. In ademonstration, social interactions that challenge learners’ ideas, cause self-reflectionon the ideas expressed and engender collaborative dialogue are necessary to promote

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a scientific understanding of a science demonstration. Such interactions may leadlearners to view their existing ideas as unsatisfactory for explaining demonstrations,and may provide opportunities for learners to evaluate alternative ideas, moving themtoward conceptual change (Shepardson et al., 1994).

The use of lecture demonstrations as a technique to increase students’ interest andlearning in chemistry has been strongly advocated by many chemistry educators(Serianz & Graham, 1998). Although demonstrations are often used in scienceclassrooms, the use of demonstrations as a teaching technique has not been sufficientlyinvestigated in terms of their appropriateness for challenging and developingchildren’s conceptual understanding (Shepardson et al., 1994).

The aim of this study was to compare the effectiveness of the conceptual changeapproach (conceptual change texts accompanied by a model and demonstrations)with traditionally designed instruction on students’ understanding of chemical equi-librium concepts. Therefore, this study aims to address the following two researchquestions:

1. Do science process skills and the treatment explain a significant portion of vari-ance in the understanding of chemical equilibrium concepts?

2. What misconceptions about chemical equilibrium are held by students afterinstruction?

Method

Subjects

Participants in this study consisted of 85 male and female undergraduate studentsenrolled in the General Chemistry-II course, from two classes given by the same lecturerin the K. K. Education Faculty of Atatürk University in Turkey. One class was randomlyassigned to the experimental group (n = 45) while the other formed the control group(n = 40). While the experimental group was taught through the conceptual changeapproach, the control group was taught through traditional instruction. During a four-week period, each group received an equal amount of instructional time and wasprovided with the same materials and assignments, apart from the conceptual changetext in the experimental group. The lessons consisted of four 50-minute periods.

Research design

In this study, pre-test–post-test control group design was used to find out the effec-tiveness of two different models (conceptual change approach and traditionallydesigned instruction).

Materials

Chemical Equilibrium Concepts Achievement Test (CECAT). In order to assessstudents’ understanding of chemical equilibrium, a concept test composed of 28

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multiple-choice questions (total of 41 items together with sub-sections of some ques-tions) was used. The test was considered as composed of 41 questions in evaluation.Some of the test items were taken from literature (Banerjee, 1991, 1995; Ozdemir,1998; Tyson & Treagust, 1999; Voska & Heikkinen, 2000) and the rest were developedby the authors. The test composed of questions that were each intended to measurestudents’ understanding of different concepts related to chemical equilibrium. In somecases, however, the same concept was tested with two different types of questions. Theitems in the test included one correct answer and three or four distracters that reflectedstudents’ probable misconceptions reported in related literature (Hackling & Garnett,1985; Hameed et al., 1993) and during interview sessions. During the developmentstage of the test, which constituted the qualitative part of the study, the following stepswere taken into consideration: first, instructional objectives related to chemical equi-librium were developed, based on the national curriculum. This step was carried outto define the content of the test. Literature related to students’ misconceptions aboutchemical equilibrium was then examined, and interviews were conducted withstudents to identify their misconceptions.

1. 2CO (g) + O2 (g) 2CO2 (g) + QWhile the above reaction was at equilibrium, temperature is increased at constant volume,

a) At the time of temperature increase, the forward reaction rate: A) instantaneously decreases B) instantaneously increases C) does not change

b) When equilibrium was re-established, the forward reaction rate:A) is higher than that of initial equilibrium stateB) is less than that of initial equilibrium state C) is equal to that of initial equilibrium state D) there are not enough data to answer the question

2. When 2CO (g) + O2 (g) 2CO2 (g) + Q reaction at equilibrium, O2 was inserted into the system at constant volume and temperature. At the time of O2 addition, the reverse reaction rate:

A) instantaneously decreases B) instantaneously increases C) does not change

3. I2 (g) 2I (g)

At constant temperature and pressure, if He (an inert gas) is inserted into the aboveequilibrium system, which of the followings occurs? A) Equilibrium position shifts to rightB) Equilibrium position shifts to left C) Equilibrium position is not affected from inert gas addition

Figure 1. Example questions measuring students’ misconceptions about chemical equilibrium concepts in CECAT

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The test was piloted and modifications were made prior to the administration ofthe test. The content validity of the test items was carried out by a group consistingof three chemistry lecturers. The reliability coefficient of the test, computed by split-half method, was found to be 0.70. The final form of the test was administered toboth experimental and control groups as a pre-test before the treatment and post-testafter the treatment. Four examples of the test questions are presented in Figure 1.Figure 1. Example questions measuring students’ misconceptions about chemical equilibrium concepts in CECAT

Science Process Skill Test (SPST). This test was originally developed by Burns et al.(1985). It consists of multiple-choice items each with four alternatives. It covers allscience areas and includes five subtests: identifying and stating the hypotheses,operationally defining, experimental design, data and graph interpretation, andidentifying variables. The test was translated and adapted into Turkish by Gebanet al. (1992). The reliability coefficient computed by Cronbach alpha estimates ofinternal consistency of test was found to be 0.81. The SPST was administered to theexperimental and control groups before instruction.

Procedure

This study was conducted over a four-week period. The experimental group was taughtusing the conceptual change approach. The control group received traditional chem-istry instruction. The topics related to chemical equilibrium were covered as part ofthe regular classroom curriculum in the chemistry course. The classroom instructionfor both groups was four lecture hours per week. The same topics related to chemicalequilibrium concepts which are dynamic nature of equilibrium, definition of equilib-rium constant, heterogeneous equilibriums, qualitative interpretation of equilibriumconstant, prediction of reaction direction, calculation of equilibrium concentrations,changing the reaction conditions, Le Chatelier’s Principle, removing products oradding reactants, changing the pressure and temperature, effect of catalyst, effect ofinert gases, were covered for both experimental and control groups. In general,students were given equal opportunities to perform the activities in each group.

Students in the control group were instructed using the traditional approach,namely the teacher provided instruction through a lecture and discussion environ-ment. Teaching relied mainly on lecturer explanation and textbooks, not takingstudents’ misconceptions into account. The students studied the textbooks on theirown before the class hour. The lecturer structured the entire class as a unit, wrotenotes on the blackboard about the definition of concepts and passed out worksheetsfor students to complete. The primary underlying principle was that knowledgeresides with the teacher and that it is the teacher’s responsibility to transfer thatknowledge as fact to the students. The lecturer described and defined the conceptsand after lecturer explanation, some concepts were discussed, motivated by lecturer-directed questions. In the regular classroom instruction, the lecturer providedinstruction through lecture and discussion to teach concepts and employed propor-tional reasoning techniques, probably coupled with algorithmic approaches to solving

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problems about relationships and calculations that involved chemical equilibriumconcepts. This classroom typically consisted of the lecturer presenting the ‘right way’to solve problems. However, the students had the opportunity to ask questions, andthe teacher was available both to answer questions and make suggestions. When anystudents of the traditional class voiced misconceptions clearly, the instructor listenedto the students, accounted for and dealt with their misconceptions and adjusted theirstrategies within a discussion environment.

Students in the experimental group were taught through the conceptual changeapproach including conceptual change texts, models and demonstrations that tookmisconceptions into account and focused on explanations that would maximize theplausibility and intelligibility of scientific conceptions. Conceptual change texts wereprepared by the researchers in the light of information obtained from the related liter-ature review and interviews. While constructing the conceptual change texts thefollowing points were taken into consideration: (a) each text aimed at transformingstudents’ misconceptions into scientific conceptions; (b) conceptual change textsidentified common misconceptions about the subject matter; (c) conceptual changetexts directly informed students that they might possess such misconceptions; (d)they activated students’ misconceptions by presenting simple qualitative examplesthat allow the misconceptions to be used to make a prediction about the situation; (e)in each of the texts, the topics were introduced with questions, and students’ possibleanswers that are not scientifically accepted were mentioned directly. In this waystudents were expected to be dissatisfied with their current conceptions; and (f) thenscientifically acceptable explanations that are more plausible and intelligible weredescribed. Also, examples and figures were included in the texts with the intention offurther helping students understand the scientific concept and realize the limitationsof their own ideas. These texts offered a set of guidelines to help students gainexperience in grasping the concepts. These guidelines provided special learningenvironments, such as identifying common misconceptions, activating students’misconceptions by presenting examples and questions, presenting descriptiveevidence in the text that the typical misconceptions were incorrect and providing ascientifically correct explanation of the situation. The teacher provided opportunitiesfor students to be involved in discussion and question and answer sessions whilestudying conceptual change texts. Students were asked explicitly to predict whatwould happen in a situation before being presented with information that demon-strated the inconsistency between common misconceptions and the correct scientificconceptions. An excerpt of a conceptual change text is given in Figure 2.Figure 2. An example of a conceptual change textDuring the implementation of conceptual change texts, each student was given aconceptual change text, where the related topic would be covered and the teacherdirected students to read the texts silently in class. After reading a paragraph in whicha question was posed and the evidence was presented that the typical misconceptionwas incorrect or a scientifically correct explanation of the concept was provided,students were asked to stop reading. The teacher then asked if anything they had justread was surprising and what they thought about the explanation they had just read.Taking the model and the demonstrations into account, the teacher discussed the

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conceptual change texts with the students. Moreover, the teacher emphasizedcommon misconceptions held by the students by asking questions related to themodel and mentioning the scientifically correct explanations of the concepts.

The analogical model used in this study, liquid transfer model, has been previouslyexplained by Russell (1988). The model uses two identical 100 ml graduated cylin-ders, and 5 ml and 10 ml graduated pipettes (one each), which must have differentdiameters. The first graduated cylinder is filled with 100 ml of colored water (red)representing initial reactants. The second graduated cylinder is left empty represent-ing no initial products. The progress of the reaction is demonstrated by dipping the10 ml pipette to the bottom of cylinder #1, and dipping the 5 ml pipette to the bottomof cylinder #2. The demonstrator then places a thumb over the top opening of eachpipette to trap the liquid in the pipette. The entrapped liquid is then transferred tothe opposite cylinder. This process is continued for few minutes until the volumes ineach cylinder no longer change. So, a state of dynamic equilibrium has now beenestablished between the two cylinders.

In contrast to the use of two 25 cm lengths of glass tubing as reported in theprevious study by Russell, we used 5 ml and 10 ml pipettes for the transferring of theliquid. This is because before equilibrium is established, it is possible to read directlythe volumes of the liquid transferred from one cylinder to another during the trans-ferring process. In this model, the volumes of the liquid in cylinder #1 and cylinder#2 represent the concentration of reactants and the concentration of products,respectively. In addition, the volumes of the liquid transferred by 10 ml and 5 mlpipettes refer to forward and reverse reaction rates, respectively.

This model suggests that the following propositions concerning chemical equilib-rium could be offered:

● While the concentration of reactants decreases, the concentration of productsincreases with time.

When does reverse reaction start in a reversible reaction?A common misconception among students is that forward reaction must be completed beforethe reverse reaction starts. In other words, students see reversibility as referring to somethingthat moves forward and then backwards, rather like a car. Moreover, focus on the productside and the reactant side of chemical equations contributes to the belief that reactionsproceed only in one direction at a time. Thus, students also think that concentrations fluctuateas equilibrium is established. However, in reversible reactions, the reactants are notcompletely consumed. In reversible reactions, instead, forward and reverse reactions takeplace simultaneously. Thus, an equilibrium mixture containing both products and reactants isobtained. At equilibrium, as forward and reverse reactions take place at the same rate, theconcentrations of both products and reactants would be constant.

Figure 2. An example of a conceptual change text

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● The forward reaction rate decreases as equilibrium approaches.● The reverse reaction rate is initially zero and increases as equilibrium approaches.● In reversible reactions, forward and reverse reactions take place simultaneously.● At equilibrium, the rates of forward and reverse reactions are equal.● After equilibrium has been established the concentrations of all the products and

reactants present remain constant with time.● Dynamic nature of equilibrium● Amounts of reactants and products are not necessarily equal at equilibrium.● With an increase in reactant concentration, equilibrium position shifts in favor of

products.● When a system at equilibrium is disturbed by increasing concentration of reactants,

the forward reaction rate increases instantaneously and then gradually decreases.● When a system at equilibrium is disturbed by increasing concentration of reactants,

the reverse reaction rate remains unchanged initially and then gradually increases.● After a system at equilibrium is disturbed by increasing concentration of reactants,

when equilibrium is re-established, the equilibrium constant does not change.● When equilibrium is re-established following an increase in concentration of

reactants, the rates of the forward and reverse reactions will be greater than thoseat the initial equilibrium.

During the application of the model in the classroom, two volunteer students helpedthe demonstrator by writing the data gathered on the board. While one of the studentsrecorded the concentrations of the reactant and the rate of the forward reaction, theother recorded the concentrations of the product and the rate of the reverse reaction.

Through performing the model, the variations of the reactant concentrations, theproduct concentrations, forward reaction rates and the reverse reaction rates as afunction of the time were given in columns I, II, III and IV respectively, as indicatedin Table 1.

The graphs shown in Figure 3 were then plotted on the board using the datarecorded in Table 1.Figure 3. As a function of time: (a) the variation of the concentration of reactants and products; and (b) the variation of the rates of the forward and reverse reactionsAfter equilibrium is reached, this model allows the demonstration of the effect ofchanging reactant or product concentrations (Le Chatelier’s Principle). In order todo this, after equilibrium is established 10 ml of colored liquid is added to cylinder#1. This represents an increase in the concentration of the reactant. Then untilequilibrium is re-established, the transfer of the liquid is carried out. In this process,as a function of time, the variations in all parameters are also shown in Table 1. Inaddition, for each equilibrium position the values of the equilibrium constants arecalculated and given in Table 2.

The steps used to present the liquid transfer model are introducing the targetconcept to be learned; cueing the students’ memory of the analogous situation; iden-tifying the relevant features of the target concept and the analog; mapping out thesimilarities between the target concept and the analog; indicating where the analogybreaks down; and drawing conclusions about the target concept (Treagust et al.,1998). During the treatment, the connections between the liquid transfer model and

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chemical equilibrium were drawn so as to allow the main concepts of equilibrium tobe demonstrated and studied through the liquid transfer model. Thus, we tried tohelp students to concretize each issue we dealt with, in order to provide a visual pointof reference for their understanding.

Table 1. The liquid transfer model and Le Chatelier’s Principle

I II III IV

Liquid volumes in cylinder #1 (ml)

Liquid volumes in cylinder #2 (ml)

Liquid transferred by 10 ml pipette (ml)

Liquid transferred by 5 ml pipette (ml)

100 0.0 8.5 0.0091.5 8.5 7.7 0.2585.0 15.0 7.1 0.7078.0 22.0 6.6 1.0072.5 27.5 6.2 1.2568.0 32.0 5.9 1.4064.0 36.0 5.3 1.60…. …. …. ….…. …. …. ….40.0 (initial equilibrium) 60.0 3.0 3.0040.0 60.0 3.0 3.0040.0 60.0 3.0 3.0040.0 60.0 3.0 3.0040 + 10 (adding reactant) 60.0 4.0 3.0049.0 61.0 3.9 3.1048.2 61.8 3.8 3.15…. …. …. ….…. …. …. ….44.0 (re-established equilibrium)

66.0 3.3 3.30

Figure 3. As a function of time: (a) the variation of the concentration of reactants and products; and (b) the variation of the rates of the forward and reverse reactions

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In Table 3, the demonstrations used in the study are briefly summarized. Two ofthe demonstrations relate to the concentration effect on chemical equilibrium and theother one concerns the temperature effect on chemical equilibrium.

At the end of the treatment, the chemical equilibrium concept test was administeredto both experimental and control groups as a post-test.

Results

Prior to treatment, an independent-samples t-test was employed to determinewhether a statistically significant mean difference existed between the control andexperimental groups with respect to chemical equilibrium achievement and scienceprocess skills. No statistically significant mean difference between the two groups wasfound with respect to chemical equilibrium achievement (t = 0.51, p > 0.05) andscience process skills (t = 1.813, p > 0.05), indicating that students in the experimen-tal and control groups were similar regarding these two variables.

Analysis of covariance was carried out to compare the effects of the conceptualchange approach and traditionally designed instruction on the understanding ofchemical equilibrium concepts by controlling the students’ science process skills as acovariate. Also this analysis identified the contribution of science process skills to thevariation in chemical equilibrium concept achievement. The analysis of data obtainedis given in Table 4.

The results indicated that there was a significant difference between the post-testmean scores of the students taught with the conceptual change approach (experimental

Table 2. The equilibrium constants

Total liquid (ml)

Liquid in cylinder #1 at

equilibrium (ml)

Liquid in cylinder #2 at

equilibrium (ml)

K(equilibrium

constant)

Add 100 ml to cylinder #1 100 40 60 60/40 = 1.5Add 10 ml to cylinder #1 at equilibrium

50 44 66 66/44 = 1.5

Table 3. Demonstrations

Demonstrations Concept Illustrated Reference

Aqueous ammonia equilibrium Le Chatelier’s Principle: effect of concentration

Summerlin & Ealy, 1988

Equilibrium of the Fe3+/ SCN− system

Le Chatelier’s Principle: effect of concentration


Equilibrium of cobalt complex Le Chatelier’s Principle: effect of temperature


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group) and those taught with traditional instruction (control group) with respect tounderstanding regarding chemical equilibrium concepts (F = 66.141, p < 0.05).

The results show that students in the experimental group performed better on thetest than students in the control group. The actual mean score of the control groupwas 21.08, and that of the experimental group was 28.58 on the Chemical Equilib-rium Concepts Achievement Test. Before the treatment, the average percentage ofcorrect responses from the students was 30% in the experimental group and 29% inthe control group. After the treatment, the average percentage of correct responses ofthe experimental group was 70%, and that of the control group was 51%. Also resultsshow that students’ science process skills made a statistically significant contributionto the variation in students’ chemical equilibrium concepts achievement (F = 16.227,p < 0.05). The degree of science process skills accounts for a significant portion ofvariation in chemical equilibrium concepts achievement.

These results indicate that the misconceptions reflected by the distracters of multi-ple-choice items in the test are the common misconceptions in a certain conceptualarea. When the proportion of correct responses and misconceptions determined bythe items analysis for the experimental and control groups was examined, strikingdifferences were indicated on several items between the two groups in favor of theexperimental group. The extent of these misconceptions for the experimental andcontrol groups is given in Table 5.

Discussion

The findings of the present study indicate that instruction based on conceptualchange texts accompanied by the model and the demonstrations (conceptual changeapproach) was more effective than traditionally designed instruction in enhancingundergraduate students’ knowledge. The participants in the experimental groupmade substantial gains in their understanding of the target concepts. This implies thatthe treatment could promote understanding of the nature of chemical equilibrium.This result of the study supports the findings of previous studies (Hynd & Alvermann,1986, 1994, 1997; Wang & Andre, 1991; Guzzetti et al., 1993; Chambers & Andre,1997; Sungur et al., 2001; Çakır et al., 2002; Alparslan et al., 2003).

During the treatment, the experimental group received instruction using concep-tual change texts accompanied by the model and the demonstrations while studentsin the control group received traditional instruction using textbooks. The resultsshowed that conceptual change texts accompanied by models and demonstrations

Table 4. ANCOVA summary

Source DF SS MS F P (sig.)

Covariate (SPS) 1 299.760 299.760 16.227 .000Treatment 1 1221.853 1221.853 66.141 .000Error 82 1514.815 18.473

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Table 5. Percentage of some common misconceptions about chemical equilibrium held by experimental group and control group after instruction

Percentage of Students

Misconceptions Experimental group Control group

Approach to chemical equilibrium1. The forward reaction rate increases as the reaction approaches equilibrium

7 30

2. In reversible reactions, the forward reaction goes to completion before the reverse reaction commences

0 20

Characteristics of chemical equilibrium3. When equilibrium is established, no forward and reverse reactions take place any more

7 55

4. At equilibrium, the concentration of reactants is equal to the concentration of products

7 57

5. Confusion between rate and extent of reaction (the greater the equilibrium constant, the faster the reaction occurs)

44 60

Changing equilibrium conditions6. When the system at equilibrium is disturbed by decreasing the concentration of reactants, the equilibrium constant will change

13 60

7. When an exothermic system at equilibrium is disturbed by increasing the temperature, the forward reaction rate will instantaneously decrease

29 60

8. When a system at equilibrium is disturbed by increasing the concentration of reactants, the reverse reaction rate will instantaneously decrease

44 63

9. When equilibrium is re-established following an increase in the concentration of reactants, the rates of forward and reverse reactions will be equal to those at the initial equilibrium

15 50

11. When equilibrium is re-established following a decrease in the concentration of reactants, the rates of forward and reverse reactions will be equal to those at the initial equilibrium

20 53

12. When equilibrium is re-established following a decrease in volume, the rates of forward and reverse reactions will be equal to those at the initial equilibrium

16 55

13. When equilibrium is re-established following an increase in temperature, the rates of forward and reverse reactions will be equal to those at the initial equilibrium

5 30

14. When equilibrium is re-established following an increase in temperature, the rates of forward and reverse reactions will be less than at the initial equilibrium

8 33

15. When the system at equilibrium is disturbed by adding the inert gas at constant pressure and temperature, the position of equilibrium will not change

29 68

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made a significant contribution to students’ understanding of chemical equilibriumconcepts. The results of this study support the notion that it is not easy to eliminatemisconceptions just by employing traditional instructional methods. The traditionalinstruction in this study emphasized lectures given by the lecturer, use of textbooksand clear explanation of important concepts to students. The lecturer undertook thetask of transferring knowledge to the students. The difference between the two strat-egies was that the conceptual change approach explicitly dealt with students’ miscon-ceptions, while the traditional approach did not. It may be concluded that a reasonfor the poor progress the students receiving traditionally designed chemistry instruc-tion made to acquire chemical concepts lies with the continued presence of themisconceptions in their conceptual framework. Table 5 shows that there is a signifi-cant difference between percentages of misconceptions of students in the experimen-tal and control groups after treatment. These results suggest that conceptual changetexts accompanied by the model and the demonstrations helped students to changetheir pre-existing conceptions or misconceptions for scientifically acceptable ones.

The greater success of students in the experimental group in this study can beexplained as follows: students in the experimental group were involved in activitiesthat helped them to revise their prior knowledge and struggle with their misconcep-tions. For example, in the conceptual change texts, emphasis was placed on students’misconceptions. Students became dissatisfied with their existing conceptions, whichallowed them to accept better explanations to the problems that were introduced. Inthis way, students were allowed to think about their prior knowledge and reflect onit. Many studies show that students change their intuitive but non-scientific concep-tions to more scientific ones by reading conceptual change texts (Alvermann &Hague, 1989; Alverman & Hynd, 1989; Guzzetti et al., 1993, 1997). However,Guzzetti (2000) reported that despite the ability of conceptual change texts to causestudents cognitive conflict and dissatisfaction with their extant beliefs, cognitiveconflict alone is not sufficient to produce conceptual change, particularly for thosewith reading and writing difficulties. So, in addition to conceptual change texts, themodel and the demonstrations were used to concretize abstract concepts regardingchemical equilibrium, such as dynamic equilibrium and reversibility. Indeed, a sociallearning environment was constructed by means of conceptual change texts, modelsand demonstrations. In the class, the students had opportunities to interact with theteacher, their classmates and the materials. Case and Fraser (1999) suggest that anovertly conceptual approach, with emphasis on the use of concrete activities, is likelyto be more successful in promoting conceptual change towards more sophisticatedand scientifically correct understandings. Similarly, the findings of the studyconducted by Treagust et al. (1996) illustrate the utility of an analogical teachingapproach for engendering conceptual change. Shepardson et al. (1994) stated thatdemonstrations can be useful if they challenge students’ existing understanding. Thischallenge to students’ understanding is most profitable when conducted in an atmo-sphere that encourages students both to test their ideas and to construct meaningthrough social interactions. Thompson and Soyibo (2002) similarly found that thecombination of lectures, teacher demonstrations, class discussions and student

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practical work in small groups significantly improved the experimental subjects’understanding of electrolysis more than their control group counterparts.

The current study revealed that there were still some misconceptions held by aconsiderable number of students even after instruction. In particular, the miscon-ceptions numbered 5, 7, 8, 11 and 15 in Table 5 were prevalent among the studentsin both groups. The most common misconception is that ‘when a system at equilib-rium is disturbed by increasing the concentration of reactants, the reverse reactionrate will instantaneously decrease’ (see misconception 8 in Table 5). Anothercommon misconception held by students in both experimental groups and controlgroups is that ‘the greater the equilibrium constant, the faster the reaction occurs’(see misconception 5 in Table 5). As stated by Bodner (1986), misconceptions areresistant to instruction. Banerjee & Power (1991) reported that about 30% ofstudents still had misconceptions about chemical equilibrium after instruction,despite using three modules on chemical equilibrium developed as a resource.These examples further emphasize the fact that the removal of misconceptions is anextremely difficult and challenging task. As discussed by Chinn and Brewer (1993)there are many ways to maintain a belief by changing the direction of resistance. Onbeing given information that contradicts a strongly held belief, an individual canignore it, trivialize it, compartmentalize it, hold it in abeyance, change an insignifi-cant part of the current belief but otherwise keep it intact, or undergo a morecomplete conceptual change.

In addition to the significant contribution of the treatment, the findings revealedthat there was a significant contribution made by students’ science process skills totheir understanding of chemical equilibrium concepts. This result confirms the find-ings of Preece and Brotherton (1997) and Sungur et al. (2001). Researchers found apositive effect of science process skills on students’ achievements in science. Scienceprocess skills are crucial for the understanding of complex chemistry concepts and thenature of scientific investigation: formulating questions, communicating, testingideas, graphing and interpreting data, etc. Thus, science process skills require higher-level thinking skills and operating on knowledge in and out of the school and are anintegral part of the learning process. Consequently, science process skill achievementis a significant predictor of achievement in chemistry.

This study led to the identification of students’ misconceptions about chemicalequilibrium and to the development of a test to determine students’ understandingin this topic. Also, it was found that the treatment resulted in an improvement inthe acquisition of chemical equilibrium concepts. The results of this studyprovided further evidence to support the findings of a growing body of literatureindicating that students hold misconceptions about a variety of chemical concepts.Conceptual change texts accompanied by models and demonstrations can providean alternative to traditional methods to remediate misconceptions about chemicalequilibrium. The findings in this article on students’ conceptions of chemical equi-librium may contribute to our understanding of some of the difficulties thatstudents experience in their chemistry classes and may help in the selection ofinstructional activities.

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Documents

The conceptual change approach to teaching chemical equilibrium