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Asia-Pacific Forum
on Science Learning and Teaching, Volume 10, Issue 2, Article 5 (Dec., 2009) |
In this study, as mentioned above, the three groups (the EG1, EG2 and CG) were used to answer to the proposed research questions. The results showed that there was no significant difference among three groups concerning their understanding of the concepts before the treatment. The first research question in the study was whether there were significant differences between the post-test mean scores of students in the experimental groups who received the CCTs as an adjunct to traditional teaching, compared to the control group students who only received traditional instruction. The results showed that students in the EGs performed much better in the post-test than the students in the CG. This finding showed that the learning approaches based on the combination of conceptual change and traditional approach resulted in a significantly better acquisition of the scientific conceptions and the elimination of alternative conceptions than traditional instruction alone. This result is consistent with the findings from the previous studies on conceptual change texts (Chambers and Andre, 1997; Guzzetti et al., 1997; Hynd et al., 1997; Özmen, 2007; Wang and Andre, 1991). However, the way the CCTs were used in this study was different from the related studies in the literature. In the present study, they were used to support the traditional teaching in the Turkish schools, but not as the main method of teaching. The reason why the students in the experimental groups were more successful than the students in the control group may be that the author (in the CCTs sessions) dealt with students’ existing ideas and alternative conceptions and provided a learning environment for them to think about their own ideas and to compare their existing concepts with new ones. Also, he provided opportunities for students to become involved in discussions while studying with the CCTs. For example, in the conceptual change texts used in this study, emphasis was given to students’ alternative conceptions. As they struggle with these alternative conceptions, the students became dissatisfied with their preconceptions. This enabled them to accept better explanations to the problems that were introduced. In this way, students were allowed to think about prior knowledge. Consequently, they were convinced that the alternative conception was incorrect and the scientifically acceptable new conception was correct. In contrast, in the control group and in the sessions of traditional teaching of the EG1 and EG2, the teacher did not consider students’ prior knowledge and alternative conceptions. He used lecture and discussion methods to transfer knowledge, wrote notes on the chalkboard about the definition of concepts covered, and gave students worksheets requiring written responses. Also, he demonstrated four experiments concerning titration, electrical conductivity of acids and bases, properties of acid and bases and effects of acids on different kinds of metal. The main difference between the two approaches was that the conceptual change approach explicitly dealt with alternative conceptions.
Table 5. Students’ alternative conceptions determined in the pre-test and post-test
EG1
EG2
CG
Pre-test
Post-test
Pre-test
Post-test
Pre-test
Post-test
Students’ alternative conceptions
f
%
f
%
f
%
f
%
f
%
f
%
1
Acids burn and melt everything (A).
15
57,69
5
19,2
13
52
6
24
12
48
8
32
2
All acids and bases are harmful and poisonous (A).
8
30,77
3
11,5
10
40
3
12
13
52
7
28
3
While bases turn blue litmus paper red, acids turns red litmus paper blue (A).
8
30,77
2
7,69
8
32
2
8
11
44
3
12
4
As the concentration of H3O+ ions in an acid solution increases, the pH of the solution increases (B).
7
26,92
0
0
9
36
0
0
7
28
4
16
5
if the pH of a solution changes, its color changes too (B)
9
34,62
1
3,85
9
36
1
4
8
32
4
16
6
pH only measures acidity (B)
11
42,31
2
7,69
11
44
4
16
13
52
6
24
7
As the value of pH increases, acidity increases (B).
10
38,46
2
7,69
10
40
3
12
6
24
2
8
8
All salts are neutral (C).
21
80,77
4
15,4
21
84
6
24
19
76
11
44
9
Salts don’t have a value of pH or have pH of 0 (C).
14
53,85
0
0
6
24
0
0
8
32
4
16
10
In all neutralization reactions, acids and bases consume each other completely (D).
16
61,54
2
7,69
16
64
2
8
11
44
6
24
11
At the end of all neutralization reactions, there is neither H+ nor OH- ions in the resulting solutions (D).
14
53,85
3
11,5
14
56
4
16
18
72
11
44
12
The indicator helps with neutralization (E)
18
69,23
1
3,85
18
72
2
8
14
56
5
20
13
The indicator changed color at pH of 7 (E).
7
26,92
0
0
6
24
1
4
7
28
2
8
14
A strong acid is always a concentrated acid (F).
9
34,62
4
15,4
8
32
4
16
6
24
5
20
15
Bubbles or bubbling is a sign of chemical reaction or strength of an acid or a base (F).
7
26,92
0
0
7
28
0
0
9
36
3
12
16
A strong acid doesn’t dissociate in water solution because its intra-molecular bonds are very strong (F).
16
61,54
4
15,4
16
64
5
20
14
56
6
24
17
The strength of an acid depends on the number of hydrogen atoms in an acid (F).
10
38,46
2
7,69
10
40
4
16
12
48
4
16
18
Species having formulas with hydrogen are acids and those having formulas with hydroxyl are bases (F).
9
34,62
1
3,85
9
36
1
4
10
40
4
16
19
Hydrolysis is the self-ionization of water (G).
8
30,77
1
3,85
8
32
2
8
7
28
1
4
20
Hydrolysis is that water decomposes into the elements hydrogen and oxygen (G).
20
76,92
0
0
18
72
0
0
20
80
8
32
Guzzetti et al. (1997) showed that texts that deal with alternative conceptions and explicitly refute them were more effective for improving conceptual change than narrative or expository ones. Diakidoy et al. (2003) also suggested that 6th grade students who read a refutational text as an adjunct to traditional instruction performed better than students who read a simple expository text or no text at all. Moreover, in the related literature there have been a great deal of studies showing that the conceptual change approach based on CCTs was more effective for promoting instruction and remedying learners’ alternative conceptions than traditional ones (Diakidoy et al., 2003; Guzzetti et al., 1997; Hynd et al., 1994; Okebukola, 1990; Horton et al., 1993; Sungur et al., 2001; Wang & Andre, 1991). Consequently, the results of the present study agreed with the previous research. In the light of these results, it can be said that conceptual change text oriented instruction is an effective teaching strategy in order to help students go through the conceptual change concerning the concepts of acids and bases.
The second research question asked whether there was a significant difference between the post-test means of the EG1 students who received CCTs before the traditional teaching and theEG2 students who received CCTs after the traditional teaching. When, the post-test mean scores of the EGs were compared to each other, it was found that the EG1 students performed much better in the post-test than the students in the EG2. In the related literature, no study examining the effect of CCTs on students’ alternative conceptions before and after traditional teaching was encountered. CCTs were commonly used after the regular classroom teaching and compared with the traditional teaching in the literature. In these studies, as mentioned above, it was suggested that groups taught by CCTs were more successful than those taught by the traditional approach alone. It could be said that the present study was original from this perspective. Although the same activities were done in the both experimental groups, finding different results was amazing. In the non-formal in-class observations, during traditional teaching, most students in EG1 were more ambitious to learn the concepts to be studied and asked more questions to the teacher than the EG2students. The reason for this may be that EG1students had studied the same concepts during the CCT sessions before the traditional teaching. For example, when the teacher explained neutralization and titration concepts and demonstrated a titration of a strong acid (HCl) with a strong base (NaOH), some students in the EG1asked the following questions: “What is the difference between the equivalence point of a titration and its end point?” “Why is pH not always 7 at the equivalence point” “Why does the equivalence point occur at a pH of 7 for titration of a strong acid with a strong base?”, etc. These questions lead to classroom discussions that were similar to those in the CCTs sessions, but the teacher failed to give satisfactory explanations to the questions. He showed some alternative conceptions too. Pardhan and Bano (2001), Mellado (1997) and Trend (2001) reported that pre- and in- service science teachers held non-scientific ideas. However, EG2 students had no questions about this concepts and found the teacher’ explanations adequate. In the CCTs sessions, classroom discussions, in which the cases where alternative conceptions in the texts seemed to be inconsistent with students’ prior knowledge, had an important influence in student’ understanding and alternative conceptions of acid and base concepts. Guzzetti (2000) argued that conceptual change/refutational texts caused cognitive conflict, but cognitive conflict was not often sufficient to cause conceptual change. Moreover, Guzzetti et al. (1995) reported that although refutational/conceptual change texts were effective on the average for groups of students, they should be supported by discussion for some students. Classroom discussions on the CCTs gave experimental group students opportunities to focus on the interpretation of phenomena and helped them build up new concepts. This finding supported the results of previous studies (Mason, 1998; Mason & Santi, 1998; Tobin et al., 1994).
The third research question asked which alternative conceptions concerning the concepts of acids and bases were held by the students who participated in this study before and after the treatment. As seen in Table 5, the results from the pre-test showed that the students in all groups held a large number of alternative conceptions before receiving formal instruction on the acids and bases. These alternative conceptions were also common among other students in many countries and well-documented in the literature (e.g., Ayas & Demircioğlu, 2002; Cros et al., 1986, 1988; Demircioğlu, 2003; Demircioğlu et al., 2004; 2005; Hand & Treagust, 1991; Nakhleh & Krajcik, 1993; 1994; Özmen et al., 2009a; Ross & Munby, 1991). After the intervention, each group showed progress in eliminating their alternative conceptions, but the experimental groups were better overall. While the students in the EG1 had corrected five alternative conceptions completely, the EG2 students eliminated four alternative conceptions. On the other hand, the CG students could remedy only one alternative conception. The results from this study support the notion that it is not easy to eliminate alternative conceptions just by using ordinary forms of instruction (like lectures, ordinary text, and labs) (Champagne et al, 1983; Driver & Easley, 1978). Because alternative conceptions are well embedded in learner's cognitive ecology and strongly held, they are resistant to change even with instruction designed to address them (Palmer, 1999; Vosniadou et al., 2001). From in-class observations during the treatment, it was revealed that some of the students in the experimental groups had difficulty understanding the reverse relation (e.g., as a solution becomes more acidic, its pH falls) between [H+] and pH. Even after studying the conceptual change text about the pH scale, some continued their claims. The common alternative conceptions held by the students were generally related to the concepts of hydrolysis, salts and neutralization (Table 3). As is known, these concepts are closely related to each other. However, the hydrolysis concept is explained without relating it to the concepts of neutralization and titration in the chemistry textbooks used in the science classroom in Turkey. Thus, students have difficulty in meaningfully constructing the concept, relating it to other concepts and developing alternative conceptions (Demircioğlu, 2003). The conceptual change text used in the present study (Appendix A) explained the concept of hydrolysis by correlating it to the titration concept and emphasizing alternative conceptions. Hence, as seen from Table 3, all students in the experimental groups correlated the alternative conception in item 20 in the post-test. In addition, most students in all groups appeared to confuse the hydrolysis concept with the electrolysis of water as determined by the informal in-class observations and the pre-CAT. Most likely the reason for this can be that the students were more familiar with the electrolysis concept than the hydrolysis due to the fact that the former was taught first in 6th grade science courses in Turkish primary schools. Another reason for this confusion may be that the last parts (-rolysis) of words ‘hydrolysis’ and ‘electrolysis’ have the same spelling and pronunciation. Another alternative conception, not determined in the pre-test, was revealed while students were reading the CCTs concerning the titration. The question on top of this text was, “Why is the pH at the equivalence point of a weak base titrated with a strong acid less than 7?”. None of the experimental group students were able to correctly answer this question because they ignored the effect of hydrolysis. Most students in EG1 and EG2 indicated that a strong acid completely ionizes, and a weak base only slightly ionizes in water producing relatively few OH- ions, and hence H3O+ ions are greater than OH- ions at the equivalence point. Namely, if one of the reactants was weak, the complete neutralization does not occur and strong one determines the pH of the resulting solution. This alternative conception was reported in the study of Pınarbaşı (2007). Some suggested that the acid would be more dominant because it would be stronger than base and the resulting solution would have an acidic pH. One possible reason of common alternative conceptions concerning acid-base concepts is that they are interdisciplinary in nature. Understanding of pH and neutralization (titration) requires the understanding and application of the knowledge of physics and mathematics because learning of these concepts requires knowledge of graphing and logarithms. Another reason can be that students may have mixed up the original and the modern interpretation of some concepts. For instance, the idea that neutralization always results in a neutral solution has been found to be quite common among the students. This is an alternative conception that stems from shifting the meaning of neutralization and the ambiguous use of the term neutral in everyday context and in the chemical context (Schmidt, 1991). The historical development (from Arrhenius’ theory to Bronsted-Lowry’ theory) shows that the term neutralization has lost its original meaning in chemistry, and that the modern definition is incompatible with the original interpretation. The term neutral in physics is used to show that there are neither positive nor negative charges. The term “neutral” has a different meaning when a neutral solution is described. In this case neutral solution contains as many H3O+ ions as OH- ions. Nakhleh (1992) pointed out the issue of language usage in science and in everyday context.
This study sought to determine whether the CCTs were more effective before or after implementing the traditional teaching on 10th grade students' conceptual understanding and alternative conceptions of acids and bases. The findings from the study suggest that studying the CCTs before the traditional teaching can enhance more students’ understanding of acids and bases than both studying them after the traditional teaching and using traditional teaching alone. The study also provides further evidence that the CCTs are more effective in remedying students’ alternative conceptions than traditional approaches. Unfortunately, in our country, most teachers ignore the assessment of students’ prior knowledge and learning needs before the instruction, although alternative teaching strategies emphasize the importance of learner’s preconceptions. As seen from the results of this study, and similar findings of other studies, a teacher who identifies students’ alternative conceptions before the instruction can more easily help students gain scientifically acceptable conceptions by using alternative teaching strategies. Firstly, pre-service and practicing science teachers should understand the importance of prior knowledge in learning, which was defined by Jonassen and Gabrowski (1993) as the knowledge, skills or ability that a student brings to the learning environment, because they are strong predictors of student achievement. Then, they should be informed about the usage of strategies of conceptual change that explicitly deal with students’ prior knowledge and alternative conceptions, due to the fact that much research indicates that there is a strong relationship between prior knowledge and performance of students.
Conceptual change texts used in this study and other studies in the related literature may be placed in chemistry textbooks for better learning. Also, teachers should be trained in the preparation and the usage of conceptual change texts. Most chemistry classes in our country have teacher-centered instruction. Therefore, during the transitional period from a teacher-centered instruction to student-oriented one, CCTs can be used as a supplement to classroom instruction to promote students' understanding of science concepts and eliminate their alternative ideas. Because this study was limited to 76 10th grade high school students in three intact classrooms, caution is advised with respect to generalize the findings to a wider context (Guba & Lincoln, 1994). This study may be considered as a small step on a shift from a teacher-centered to a student-centered strategy in Turkish schools. For further work, similar studies can be constructed for other topics or concepts of secondary chemistry education and with larger sample sizes. Studies on conceptual change texts accompanied by other methods such as concept mapping, laboratory activities done by students and analogies can be carried out. Teaching strategies taking students’ alternative conceptions into consideration may, as suggested here, also be useful for enhancing meaningful learning. In addition, curriculum designers, textbook writers and teachers should take these strategies into consideration when developing new science curriculum. In short, when suitable conceptual change strategies are used in the teaching of the acid and base concepts, they are more likely to cause a significantly better removal of misconceptions and acquisition of scientifically sound concepts.
Acknowledgements
This work was supported by the Research Fund of Karadeniz Technical University, Project Number: 2005.116.04.3
