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Asia-Pacific Forum
on Science Learning and Teaching, Volume 10, Issue 2, Article 5 (Dec., 2009) |
The Concept Achievement Test (CAT): First 15 items in the CAT were taken from the previous studies (Demircioğlu et al., 2005; Özmen et al., 2009a). The other items were developed by the researcher according to the instructional objectives and students’ alternative conceptions reported in the literature. Each item on the CAT was constructed based on a methodology used by Peterson, Treagust and Garnett (1986) and Treagust (1988). To confirm content validity, the CAT was examined by a group of experts comprising two university chemistry educators and two high school chemistry teachers who have been teaching for over twenty years at the central lycées in the city of Trabzon. Its reliability coefficient (KR20) for the pilot study was found to be 0.83 using the Cronbach Alpha formula, whilst this value was 0.87 for the real study. The final version of the CAT consists of twenty-five questions and the conceptual areas covered by the test are presented in Table 2.
Table 2. The topic the each test item attempts to measure
Covered areas
Definitions of acids and bases: 1, 2, 3
Characteristics of acids and bases: items 4, 5, 6, 7, 8
Titration and neutralization: items 9, 10 ,11, 12
Weak acid and base ionizations: items 13, 14, 15, 16
pH scale: items 17, 18, 19
Indicators: items 20, 21, 22
Hydrolysis and buffer solutions: items 23, 24, 25
Development of conceptual change texts
Twelve conceptual change texts were prepared by the researcher based on information gathered from a review of literature about students’ learning difficulties in acid-base chemistry and alternative conceptions determined by the CAT. Conceptual change texts used in the study were comprised four main parts. The first part contained a question about the concept to be studied in order to activate preconceptions of students and cause dissatisfaction with their current conceptions. The students were expected to respond the question and explain their answer individually. In the second part, students’ alternative conceptions were directly mentioned. In this way, the students were expected to be dissatisfied with their existing ideas. In the third part, scientifically acceptable explanations related to concepts were given. These explanations were supported with concrete examples and figures to help students’ understanding of the concept. In the final part, the students were provided with different statements related to the concept in order to prove that the new concept is more fruitful than their preconceptions. In this way, students’ alternative conceptions tried to be changed into scientific ones. Each text aimed to remedy alternative conceptions determined by the literature and the CAT. In the study, twenty alternative conceptions, which were listed and coded in Table 5, were taken into account in six conceptual areas. In each text, one, two or three alternative conceptions were dealt with. Conceptual areas covered by the CCTs were: (a) properties of acids and bases (two texts, one for A1 and A2, the other for A3 and B3 in Table 5); (b) salts (one text for C1 and C2 in Table 5); (c) hydrolysis (one text for G1 and G2 in Table 5); (d) neutralization and titration (three texts, one for D1, another for D2, and the other 3 for E1 and E2 in Table 5;, (e) pH scale (two texts, one for B1 and B4, the other for B2 and B3); and (f) strength of acids and bases (three texts, one for F1, one for F2, F4, and F5, and the other for F3 in Table 5). The texts were validated by a panel of five experts, consisting of three experienced chemistry teachers and two chemistry education professors. One of the texts used in the study was given in Appendix A, as an example.
Three groups, two EGs and one CG, one chemistry teacher and the researcher participated in the study. Firstly, the CAT was administered to the groups as the pretest two months before the intervention. In the intervention phase, EG1 students were taught by the researcher using the CCTs for two weeks (6 hours). Afterwards, the teacher taught using the traditional approach for three weeks (9 hours). On the other hand, the teacher taught EG2 students first using traditional approaches for three weeks (9 hours), and then the researcher taught them by using CCTs for two weeks (6 hours). Both EG1 and EG2 students took a total of a 15 hours course related to acids and bases. The CG students were taught by the teacher using only the traditional approach for five weeks (15 hours in total). Table 1 summarizes the teaching procedure throughout the study.
Teaching approach used for the control group
The teacher mainly used lectures and wrote notes on the chalkboard to teach the concepts of acids and bases. During the first week, the teacher explained the Arrheniusdefinition of acids and bases, the formation of the hydronium ion, limitations of the Arrhenius definition, the Bronsted-Lowry acid-base theory and Lewis’ definition and then wrote examples for each definition on the chalkboard. The students listened to the teacher’s lecture, took notes and gave examples of acids and bases. After the teacher’s explanations, some of the concepts were discussed. In the second week, he explained the characteristics of acids and bases and gave examples for each of the properties. Then the teacher demonstrated two experiments in the classroom involving the effect of acids on metals (magnesium and zinc) and electricity conductivity of acids and bases (NaOH, HCl, lemon). The students observed and took notes. He passed out the worksheets, including conceptual questions about the definitions and characteristics of acids and bases. While the students were studying on the worksheets requiring written responses, the teacher walked around inside the classroom and helped the students when they needed. During this activity, the students had the opportunity to ask questions. The worksheets were collected and corrected by the teacher, and the students reviewed their responses after correction In the third week, the teacher explained the pH concept and showed how to solve algorithmic problems related to the pH concept and to test the pH of soft drinks, dish washing liquids, lime juice, etc. by using pH paper and litmus. The students took notes and solved algorithmic problems. In the fourth week, the teacher explained the neutralization and titration concepts by demonstrating an experiment in the classroom involving the titration of a strong acid (HCl) with a strong base (NaOH) and showed how to perform the titration calculations. In the final week, he summarized all the concepts in the acid-base unit and passed out the worksheets including algorithmic and conceptual questions about all the concepts of acids and bases. They were collected and corrected by the teacher. The students in the control group did more exercises (generally procedural questions) about each concept in the acids and bases unit than those in the experimental groups because they had more time. On the other hand, students in the experimental groups did not perform the worksheets.
Teaching approach used for the experimental groups
The same instructional procedure was used in EG1 and EG2, except for the implementation time of the CCTs. While the CCTs were implemented before the traditional instruction in EG1, it was applied after the traditional instruction in EG2 (see in Table 1). In a typical instructional sequence, the CCT was handed out to students and they were asked to read the question at top of it carefully and silently. Then, students were asked to stop reading and were given time to think. Then, they were asked to write their answer in blank area under the question. This step attempted to activate students’ alternative conceptions if they existed. After this process finished, students verbally stated their beliefs and were discussed with the whole classroom. Then, they were asked to read common alternative conception(s) in the text and to compare with ideas they had just written. On one hand, students who had alternative beliefs were helped to recognize the weakness or lack of their conceptions and to develop cognitive conflict; on the other hand, all of the students were encouraged to notice the different alternative beliefs. After the classroom discussion, scientific explanations related to concept were presented to provide intelligibility and plausibility. A few willing students were asked to assess the text. Finally, the researcher summarized it for all students. After the CCTs, the students in EG1 were exposed to the traditional teaching. During this period, the students were taught by the teacher and dealt with the concepts of acids and bases. The students in the experimental groups (EG1 and EG2) studied the concepts in the acid and base unit twice.
