gmail.comChemical Education Journal (CEJ),
Vol. 14, Issue 1 /Registration No. 14-6 /Received June 15, 2011.
URL =
http://chem.sci.utsunomiya-u.ac.jp/cejrnlE.html
gmail.comAbstract
In this study we investigated students' misconceptions, erroneous
and limited conception of the pH concept in order to achieve their
full, meaningful and permanent understanding. We used written
exams and semi-structured interviews were used. On concluding
this study, we found that many students had misconceptions about
the pH concept. Furthermore, they were unable to transfer their
mathematical knowledge to chemistry. They could not use mathematical
knowledge in chemistry. They did not use analogy. This problem
is a major obstacle to learning. 19-55% of students had misconceptions
about pH and pH concepts. 83% of students did not know the meaning
of pH or why we use it. 5% of students miscalculated pH solutions
or pH problems. These are similar to the results found in existing
literature. In addition, we discovered where students made mistakes
and did not fully understand. All of these issues affect the learning
of the pH concept, e.g. calculating the pH, understanding the
pH scale, the effect of pH on acidity and the effect of pOH on
basisity.
Keywords : misconception, pH, pOH, limited conception, erroneous conception.
Appendix B. (Interviewer Questions)
Toplis (1998) reported on year 8 pupils' ideas, conceptions and misconceptions about acids and alkalis investigated before and after a teaching sequence in a small-scale research project. Some of their misconceptions were highlighted, and it was concluded that pupils' understanding of acids could be enhanced, that their ideas about indicators were encouraging, but their understanding of alkalis could pose a problem. Also, Toplis compared students have concepts, misconceptions and their ideas on pre-education and post-education. It was seen that many of the students had misconceptions or limited conceptions of acid-base. When students answered the question, they chose in respect of colours, for example: if litmus paper was red, it was acid. Oversby (2000), focused on the question "Can a strong acid form a weakly acidic solution?". This study set out to show the possible confusion arising from the terms "weak acid" and "weakly acidic" in different contexts. A framework for developing secondary-school students' thinking about the concept of pH in a logical way is given, together with some suggestions for avoiding incorrect explanations while at the same time retaining simplicity. In addition, this study aims to clarify some aspects of pH which can be confusing at this level, for example the difference between weak acid and weak acid solution. Oversby also investigated the teaching of the pH concept in secondary school and explained it very well. Vidyapati and Seetharamappa (1995), studied acid-base concepts at high school with second year class students. They observed that 70% of the students thought that, when acid and base were mixed, the solution resulting from the neutralization reaction occurred, but 15% of the students thought that some change occurred in the pH of the solution. Cross et al. (1986) investigated the acid-base issue and its gradients with first year university students. Their study was a follow-up to an earlier study in which they assessed the knowledge and conceptions of fundamental notions in chemistry in new students first starting university. They examined to what extent, after one year of study at university level, students' conceptions had evolved and how their knowledge of scientific theory had progressed. According to 17% of the students, pH was a measure of acidity. They also found that the students' conceptions were modified correctly, but sometimes incorrectly and the results obtained seemed to indicate that the ambitious aim of teaching (better acquisition of important notions by students) was far from being attained. The study also showed that for some topics the teaching of chemistry had too formal a character. To rectify this situation, they proposed that practical work must include problems that are not only chemical in nature. All these student-based studies were about the subject of acid-base, but they referred to the pH concept at the same time.
These concepts have been recognised as key concerns in science education and, as a result, many papers have been written about them. Not many students are developing a suitable understanding of these concepts. This fact is recognised by scientific acknowledgement (Nakhleh, 1992; Renström, Andersson, and Marton, 1990; Stavy, 1988; Treagust, 1988). It is a well established fact that in interviews and tests, students express a variety of nonscientific ideas (Duit, 2007). Since the mid-seventies, it has been recognised that students understanding of scientific events are different from scientific ideas and scientific concepts (Ebenezer and Fraser, 2001). Students' perceptions take on different forms. These forms are mainly misconceptions, preconceptions, alternative frameworks, children's science, limited conceptions (Ayas and Coştu, 2001; Ünal, 2003; Çalık, Ayas and Ebenzer, 2005; Çalık and Ayas, 2005; Köse, Coştu and Keser, 2002).
Decidedly, the main problems are misconceptions, limited conceptions and preconceptions of students and educators alike (Zoller, 1990). Students' misconceptions, limited conceptions and preconceptions are obstacles to the educational progress (Ayas and Demirbaş, 1997; Garnett and Treagust, 1992; Quiles-Pardo and Solaz-Portolés , 1995). For this reason, these problems in science education need to be determined and addressed. Many studies have been conducted on the subject of acid-base but there hasn't been much work done on the pH concept and misconceptions of it.
Two aims are addressed in this review of our research:
The process of acquiring scientific knowledge follows certain steps or events. These steps or events have different dimensions. Below, we present a research loop of the process.
llllllllllllllllll
llllllllllllllllllllllllllllllllllllllllllllllll
lMeasurement
/ Observation
In Figure 1, "Social Events"
are lessons or lectures. "Functional Questions/Hypothesis"
are tests and exams. "Measurement/Observation" are test
results and interviews. "Statistical Process" is comment
on test results. "Symptoms" are test results and our
conclusion.
In this study science teacher candidates' misconceptions, preconceptions, erroneous ideas and limited understanding of the pH concept were investigated. The pH concept is special in chemistry. Written exams and semi-structured interviews were used in Erciyes University's Faculty of Education for the evaluation of science teacher candidates. Teacher candidates came from all over Turkey.
In the social events section the students' background in chemistry was considered. In the functional questions/hypothesis section a written exam and semi-structured interviews were used. In the measurement/observation section students were asked questions relating to misconception, preconception, erroneous ideas and limited conception, because the problems students face in the education system are not related to only one concept. In addition we asked mixed and standard "Why?" questions in both the exam (Appendix A) and interview (Appendix B). Mixed questions led to discussion and so helped determine some students' problems. Questions were especially categorized with regard to measurement issues, see Table 1, such as literature (Morgil, 2002).
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Misconceptions lead to problems in the understanding of other concepts. Misconceptions are strongly and persistently held by students. Hence, misconceptions differ from mistakes, which "can be recognized by the students themselves when presented with an accepted conception" (Abimbola, 1988). Erroneous ideas are the result of mistaken learning in the education process (Zoller, 1990). Limited conceptions are not the result of mistaken learning, but they arise when targetted subjects or concepts are not fully understood (Toplis, 1998). Different types of misconceptions, limited conceptions and erroneous ideas are dealt with in the questions given in the Table 1 (see also Appendix A and B). Morgil ,2002) prepared some questions about the pH concept, see in Table 2. Others (Cross, et al., 1986; Vidyapati, et al., 1995) also studied the acid-base concept. They also carried out research and showed that, in their experience, students considered pH only as a measure of acidity. They asked questions about pH and so understood students' misconceptions. In the statistical process section, the exam and interview results were examined (See Tables 5 and 6 below). In the symptoms section we assessed students' learning problems.
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| Acidity Constant | If acidity constant increase, does acidity increase? |
| pOH | If pOH increase, does it's base increase? |
| pOH | If the pOH increase, does it's acidity increase? |
| pH | If a solution's pH is 4, its concentrate is 3x10-7, 0.10 M |
| pH | If a solution's concentrate is 5x10-4 M, its pH is 7, 10, 11 and 12 |
| pOH | Is it possible to have a solution with a pH of zero? |
We can see the distribution of student groups below in Table 3. Student numbers and their age range are very important to success ratio. Nevertheless, our students were roughy the same age and they belonged to the same education system.
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The subject of acid-base was studied in a very detailed manner by Inci Morgil et al. (Morgil, 2002). They did research on misconceptions related to acid-base and pH (Table 2).
Listed below are some questions related to the pH concept. We can see their structure and the areas that were asked and what the purpose of the questions were (Table 4).
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| What is the pH mean and why we use? |
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| Calculate of pH |
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| pH scale |
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| Ka relation with pH |
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| Litmus paper relation with pH |
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| Effect of pH on acidity |
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| Effect of pOH on basisity |
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In Table 5, we can see the source of students' problems. 83% of students have a limited conception of pH usage and its' meaning. Cross, et al (1986) emphasized that 17% of students understood pH as a measure of acidity. In our study, 20% of students understood pH merely as a measure of acidity. Although Inci Morgil et al. (Morgil, 2002) pointed out that students had some problems with the calculation of pH and pOH, only 5% of students in our study were unable to make calculation of the pH. This ratio is lower than that in Morgils' study. At the same time, the questions asked about acid-base were related to equilibrium problems. Students had erroneous and limited conceptions which focused on mathematical problems, as also shown in Toplis' study (1998). Toplis (1998) researched conceptions and misconceptions about acids and alkalis, and he found that many students had misconceptions and limited conceptions (especially in regard to litmus paper and pH). In his study, some clues were also found as to the reasons for misconceptions in the early stages of education (Ka relation with pH: 35%, Litmus papers, relation with pH: 19%) and limited conceptions (Ka relation with pH: 5%) in the later stages of education. Inci Morgil et al (Morgil, 2002) stressed that students had misconceptions about the effect of pH and pOH on acidity and basisity. In my study, we found that 44% of students had misconceptions about the effect of pH on acidity and 33% of students also had misconceptions about the effect of pOH on basisity.
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| What is the pH mean and why do we use it? |
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| Calculate of pH |
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| pH scale |
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| Ka relation with pH |
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| Litmus paper relation with pH |
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| Effect of pH on acidity |
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| Effect of pOH on basisity |
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| What is the pH mean and why do we use it? |
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| Calculate of pH |
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| Calculate of complex pH problems |
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| pH scale |
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| Ka relation with pH |
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| Litmus paper relation with pH |
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| Effect of pH on acidity |
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| Effect of pOH on basisity |
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According to 20% of students, pH was seen only as a measure of acidity. In their answers, they said that pH= -log [H3O+], so it showed only acid concentration. 74% of students said that pOH was never bigger than 14. 66% of students said that pOH was never zero. 70% of students said that pH was never negative. They thought that pH and pOH could only be between 0-14, because of pH and pOH scales which were pH + pOH = 14. 83% of students didn't know the meaning of the p function. Other students believed that chemists used the p function because hydronium ion concentration was so small. According to some students, pH was a logarithm of hydronium ion concentration. 33% of students had difficulties in distinguishing pH and pOH scales in the weak acid-base questions. Although 95% of students calculated the pH for hydronium ion concentration with ease, they didn't answer acid-base questions related to equilibrium problems. In general, they had difficulties with mathematical expressions and their meanings in complex problems (Table 6). Table 6 shows students' success in the exam. Mean and standard deviation were calculated. This exam was out of 80 points. Each question was worth 10 points, but sometimes students gave near correct answers, so partial points were given for those answers. A T-test or ANNOVA was not required in this study because students were roughly the same age, belonged to same gender groups and had similar educational levels. In fact, they did well in questions such as the simple calculation of pH (60.10 ± 3.6), pH scale (44.50 ± 2.3), Ka relation with pH (50.00 ± 2.2), litmus paper relation with pH (64.80 ± 2.8), the effect of pH on acidity (52.80 ± 3.1) and the effect of pOH on basisity (53.60 ± 3.6). However when we looked at the interviews we could easily see the problem. Because the exam comprised of mixed questions (test and classic questions), the students gave different answers to questions in the interview. (Interviewer: I, Student: S). This is taken form Appendix B.
I: Why do we use the p function?
S: For hidronium ion concentrate, because it is so small. If we calculate the pH, we can easily understand the pH amount.
I: Is pH only a measure of acidity?
S: Yes
I: Why? Can't you calculate the pOH if you know the pH?
S: Because pH = - log [H3O+], so it is only an indicator of pH
I: Ok. What is the pH of 1×10-4 M H3O+
S: 4 (but he couldn't calculate the complex pH problems in Appendix B. Questions 8 and 9)
I: Does pH increase or decrease if you add 2-3 mL 1 M HCl to a solution with a pH of 3
S: Increase
I: Why?
S: Because, when I add HCl to a concentration of hydronium it increases.
When we mentioned the pH scale, the student understood his mistake. He mixed up pH and pOH scale when he answered questions too quickly. In his view, pH was an indicator of hydronium ion concentration. This interview showed evidence of misconception, limited conception and erroneous ideas. It also showed that students had major difficulties in calculating complex problems (10.20 ± 1.10), understanding what pH means and why it is used (13.60 ± 1.70); in regard to the exam it also showed that students sometimes had difficulties in understanding the pH scale. They not only gave unsatisfactory answers in the exam but also in the interviews.
In this study, we found something similar to the findings of other studies (Morgil, 2002; Toplis, 1998; Cross et. al., 1986; Vidyapati, et al., 1995). However, unlike other studies we found that students' problems with regard to misconceptions continue into the next stage of their education. In addition, we found some clues concerning students' problems. In particular, they were unable to transfer their mathematical knowledge to chemistry subjects. In addition, they did not understand mathematical functions or their means and how or where to use them. This is an inter-disciplinary problem and is a very important one.
In particular, we can see that students have misconceptions. Misconceptions are major problems in all stages of education. Misconceptions are quite resistant to change (Fischer, 1985). Therefore, it is difficult to remedy them and to provide meaningful learning by using traditional teaching methods. Perhaps, concept cartoons (See Keogh and Naylor, 1999) are one alternative teaching method, which might highlight visuality. In order to avoid misconceptions on this issue effective methods in removing misconceptions, such as the use of concept maps (Novak and Gowin, 1996; Anderson et. al., 2004), conceptual change texts (Chi and Roscoe, 2002) and computer models (Funda Örnek, 2008) are suggested.
My thanks to Dr. İbrahim Bayazit, head of mathematics education, for his contribution to this study. My thanks also to Fatma Bozkurt for her contribution.