Comparison of the effects of conceptual change texts implemented after and before instruction on secondary school students’ understanding of acid-base concepts

Acids and bases cover an important part of the 10th grade chemistry curriculum. The mastery of concepts in this unit requires the mastery of other fundamental chemistry concepts, such as chemical bonding, chemical equilibrium, mole, nature of solutions, particulate nature of matter, chemical reactions and chemical change. Therefore, students have difficulty understanding acid-base chemistry and have held serious alternative conceptions at various grade levels (Bradley & Mosimege, 1998; Cross et al., 1986; Cros et al., 1988; Demerouti et al, 2004; Demircioğlu et al., 2004; Demircioğlu et al., 2005; Hand & Treagust, 1991; Nakhleh & Krajcik, 1993, 1994; Özmen et al., 2009a; Ross & Munby, 1991; Schmidt, 1991; Sisovic & Bojovic, 2000; Shappard, 2006; Toplis, 1998). Although there are many studies identifying students’ alternative conceptions of acids and bases in science education literature, studies on how these alternative conceptions can be treated are rare (Hand & Treagust, 1991; Demircioğlu et al., 2005; Özmen et al., 2009b). Christianson & Fisher (1999) emphasized that identifying students’ alternative conceptions are very important, but undoubtedly, finding ways to eliminate or prevent these conceptions is more important. Hence, researchers in science education have focused on developing alternative methods for changing students’ alternative conceptions into scientific ones (Pfundt & Duit, 1991). The best-known conceptual change model originated with Posner et al. (1982) and was refined by Hewson (1981) and Hewson and Hewson (1984). The model has been accepted as an effective instructional model to restructure learners’ alternative conceptions. The model describes four necessary conditions (dissatisfaction, intelligibility, plausibility and fruitfulness) for conceptual change. Only after these conditions have been met can students experience conceptual change. Cognitive conflict is often considered an important factor in conceptual change (Hewson & Hewson, 1984).

Several researchers have shown that the conceptual change approach can be effective at changing students’ chemistry conceptions (Basili & Sanford, 1991; Ebenezer & Gaskell, 1995). However, the original theory of Posner et al. (1982) has been criticized for ignoring the learners’ motivational beliefs including goals, purposes, intentions and metacognitive awareness (Niaz et al., 2002; Pintrich et al., 1993; Sinatra and Pintrich, 2003). Sinatra and Pintrich (2003) suggested these factors may also promote or obstruct conceptual change. Another criticism, from a socio-cultural perspective, is that conceptual change is not only an internal cognitive process but one that happens in wider situational, cultural and educational contexts (e.g. Saljo, 1999; Vosniadou, 2008a, p.XIX; Duit et al. 2008; Treagust & Duit, 2008). Moreover, many researchers suggest that conceptual change is a slow and gradual process rather than a dramatic, gestalt shift that happens over a short period of time (Vosniadou, 2007; 2008). Vosniadou (2007) also criticized the conceptual change theory because it overemphasized the effect of cognitive conflict. Despite these criticisms, teaching methods such as analogies, concept mapping, worksheets, hands on activities and conceptual change texts (CCTs), based on Posner et al.’s (1982) conceptual change model, have still been affective in eliminating alternative conceptions (Hynd et al. 1997; Özmen and Yıldırım, 2005; Özmen et al., 2009b; Taştan et al., 2008). From these, CCTs are designed to make students aware of their inaccurate preconceptions and help them change their non-scientific conceptions toward more scientific ones through the use of explanations and examples (Hynd et.a1.1994; Pabuçcu & Geban, 2006). In the CCTs, a challenging question which was prepared to activate students' preconceptions and to provide dissatisfaction with their own ideas is first presented. Then, the identified alternative conceptions of the students are directly mentioned. Next, students’ alternative conceptions are challenged by introducing common alternative conceptions followed by evidence that they are wrong (Roth, 1985). Finally, correct scientific explanations supported by examples are presented (Başer & Geban, 2007). Science education literature contains several studies conducted to determine the effect of CCTs on students’ conceptual understanding (e.g., Canpolat et al., 2006; Chambers & Andre, 1997; Çakır et al., 2002; Özmen, 2007; Qian and Alverman, 1995; Skopeliti & Vosniadou, 2006). The results from these studies showed that the strategy was effective in creating conceptual conflict and meaningful learning for students. In these studies, CCTs were commonly used after regular classroom teaching and were compared with the traditional teaching. On the other hand, there are no studies trying to determine the effects of CCTs implemented before regular instruction.

There has been a shift from a teacher-centered to a student-centered teaching strategy in Turkish schools based on the reconstruction the Faculties of Education implemented in 1998. However, the success of the project is less than the expected level so far (Ayvacı & Devecioğlu, 2009; Çakan, 2004; Çakır & Çimer, 2007). Therefore, the use of CCTs and other conceptual change strategies as a supplement to classroom instruction seems to be necessary. Educational research suggests that alternative conceptions may interfere with students’ learning of other scientific concepts (Özmen et al., 2009a; Palmer, 1999). Therefore, it is believed that the application of CCTs before instruction may decrease the formation of new alternative conceptions growing out of the instruction. It is crucial for students to discover and remedy their alternative conceptions so they have an accurate perception of the chemistry content. Moreover, the author believes that it may be more effective in eliminating students’ existing alternative conceptions and acquiring new understandings on the concepts of acids and bases than compared to the implementation of CCTs after instruction. He also believes that instruction based only on CCTs may not be sufficient as a sound understanding of acid and base concepts. However, the instruction should be supported with CCTs or contemporary teaching techniques including various laboratory activities. With this in mind, this study attempts to examine whether the application of CCTs are effective in 10th grade students' conceptual understanding and alternative conceptions about acids and bases before or after the instruction.

The purpose of the study

The main purpose of this study was to investigate and compare the effect of conceptual change texts implemented before and after the traditional teaching on students' conceptual understanding and alternative conceptions of acids and bases. The specific research questions in this study were:

Are there statistically significant differences between students in the control group and students in experimental groups in terms of their understanding of the concepts of acids and bases?
Is there a statistically significant difference between experimental group 1 (EG1), which studied conceptual change texts before the traditional teaching, and experimental group 2 (EG2), which studied conceptual change texts after the traditional teaching, in terms of students’ conceptual understanding of the acid and base concepts?
Which alternative conceptions concerning the concepts about acids and bases are held by the students before and after the treatment?

Research design

A quasi-experimental design, which is a form of experimental research, was used in the study (Robson, 1998). One control and two experimental groups were used in the study. A summary of the methods used in each group is given in Table 1.

Table 1. The methods used in each group

Groups	1th week	2th week	3th week	4th week	5th week
EG1	CCTs		Traditional teaching
EG2	Traditional teaching			CCTs
CG	Traditional teaching (more exercises, examples)

As can be seen in Table 1, each group was exposed to traditional teaching in different durations. The groups were taught by the same teacher who had twenty-one years of chemistry teaching experience and has a master’s degree in chemistry education. The conceptual change text sessions for both experimental groups was conducted by the researcher and lasted for 6 hours. The time devoted to traditional teaching sessions was 9 hours. Each group was given the pre-test and post-test to measure the effects of the treatment, both before and after exposure to the independent variable observed during the treatment.

Participants

76 10^thgrade students from three chemistry classes in a secondary school voluntarily participated in the study. Two of the classes were randomly assigned as the experimental groups and the other as the control group. Each teaching approach used in the study was randomly assigned to each class. Experimental group 1 (EG1) studied the conceptual change texts before the traditional teaching and consisted of 26 students (16 boys and 10 girls) while the experimental group 2 (EG2) studied the conceptual change texts after the traditional teaching and consisted of 25 students (18 boys and 7 girls). The control group (CG) was taught using only traditional approach and consisted of 25 students (14 boys and 11 girls). There were four chemistry teachers in the school where the study was conducted, and only teacher volunteered to participate in the study. The chemistry course in the school was taught in three 45-minute periods per-week.