Facilitating Conceptual Change in Acid-Base Concepts

Facilitating Conceptual Change in Acid-Base Concepts



The Middle East Technical University, Department of Secondary Science and Mathematics Education, Ankara, TURKEY

Paper presented at the British Educational Research Association Annual Conference, University of Glamorgan, 14-17 September 2005


The main purpose of this study was to determine the effect of conceptual change oriented instruction on 10th grade students’ understanding of acid-base concepts. 63 tenth grade students from two classes of a chemistry course participated in the study. There were two groups in the study. There were two groups in the study. The experimental group was instructed by conceptual change oriented instruction while the control group was instructed by traditionally designed chemistry instruction over a period of four weeks. The effect of the treatment on dependent variables; chemistry achievement related to acid-base concepts measured by Acid-Base Concepts Test and gender was examined. Independent t-test and Analysis of Variances were used for testing the hypothesis of the study. The results showed that the conceptual change oriented instruction group had a significantly higher score with respect to achievement related to acid-base concepts than the traditionally designed chemistry instruction group. In addition, there is no difference between boys and girls in terms of understanding of acid-base concepts.


The content of science and the way that links between ideas are organized play an important role in the learning process. The procedures used by the learner to represent and organized knowledge and the learner’s epistemology and ability level are all crucial factors that influenced the manner in which students learn (Tyson, Venville, Harrison, & Treagust, 1996). Learning is the interaction between what the student is taught and his current ideas or concepts (Linn, 1987). Learning is concerned with ideas, their structures and the evidence for them. It is not simply the acquisition of a set of correct responses, a verbal repertoire or a set of behaviours (Posner, Strike, Hewson, &Gertzog, 1982).

Research has indicated that students often construct their own theories about how the natural works prior the formal science education, but their theories are frequently contrary to those of scientists (Osborne & Freyberg, 1985). Recently, science educators have focused their attention on how students learn and the factors which influence their learning. It is established that, during everyday life, children develop their own ideas that they use to make sense of natural phenomena they experience in the world around them (Anderson, 1986). Students’ self-constructed conceptions have been referred to in the literature as misconceptions, alternative conceptions, preconceptions, naïve conceptions, etc. (Driver & Easley, 1978; Krishnan & Howe, 1994). Throughout this paper, the term “misconceptions” has been used to refer to these ideas that are not in agreement with accepted scientific ideas.

Dykstra, Boyle, and Monarch (1992) summarized the meaning of misconceptions as;

  1. The mistaken answer students give when confronted with a particular situation.
  2. The ideas about particular situation students have which invoke the mistaken answer.
  3. The fundamental beliefs students have about how the world works, which they apply to a variety of different situations. These are beliefs in an explanatory sense about causality.

There are a variety of sources of misconceptions. These are: experiences encountered in their life (Head, 1982; Qian & Guzetti, 2000); traditional instructional language (Bergquist& Heikkinen, 1990); teachers, mismatches between teacher and students knowledge of sciences (Hodge, 1993); chemical terms that have changed their meaning (Schmidt, 1999; Schmidt, Baumgartner, & Eybe, 2003) and textbooks (Stake & Easley, 1978). Misconceptions are resistant to change, persistent and difficult to extinguish even with instruction designed to address them. Also, the misconceptions learners may hold generally hinder their subsequent learning (Ben-Zvi, Eylon, & Silberstein, 1986; De Vos & Verdonk, 1987; Haidar & Abraham, 1991; De Posada, 1997).

A helpful course of action would be to include questions on examinations that specifically probe for misconceptions. This would accomplish two goals. Educators would have a more accurate estimate of students’ actual cognitive structures, and students might give more serious thought to understanding the concepts. Students would then have a better chance of becoming meaningful learners of chemistry (Nakhleh, 1992). In order to identify and analyze misconceptions paper test like multiple choice, free response test, concept map, simple questionnaire, and short test can be used.

Students’ misconceptions in school sciences at all levels constitute major problem of concern to science educators, scientist-researchers, teachers and students (Johnstone & Kellett, 1980). It is known that chemistry is one of the most difficult subjects in secondary schools. Therefore, many of the students have difficulties in understanding fundamental concepts (Kavanaugh & Moomaw, 1981). Research on students’ understanding of chemistry concepts has revealed that students have many misconceptions. Many of the topics about which students hold misconceptions are basic to chemistry knowledge and are interrelated. Two of these fundamental concepts in chemistry are acids and bases. Beginning students are often confused by the many subtleties of acid-base chemistry. Within high school chemistry, the topic of acids, bases, and pH is particularly challenging because the student must possess a deep understanding of atoms, molecules, ions, and chemical reactions. Therefore, these concepts are related to many of the other chemistry concepts, such as the nature of matter, chemical equilibrium, chemical reaction, stoichiometry, and solutions. In the literature, there have been a number of studies that address various aspects of students’ understanding about acids and bases (Cros, Chastrette, & Fayol, 1988; Nakhleh & Krajcik, 1994; Sisovic & Bojovic, 2000).

Hand and Treagust (1991) investigated student achievement and science curriculum development using a constructive framework. The teaching strategy of conceptual conflict was used in the curriculum development. Individual semi-structured student interview were concluded three months prior to the students being involved in the acids and bases topic. From these interviews, the students’ knowledge was ascertained and five misconceptions about acids and bases were identified and used as the basis of the teaching strategy. These were an acid is something which eats material away, an acid can burn you; testing of an acid can only be done by trying to eat something away; to neutralize is to break down an acid or to change from an acid; a base is something which makes up an acid; and a strong acid can eat material away faster than a weak acid.

Nakhleh and Krajcik (1994) investigated changes in secondary students’ understanding of acid, base and pH concepts before, after and during a series of acid-base titrations using three technologies: chemical indicators, pH-meters, and microcomputer-based laboratories. It is established that some of students who participated in the study had the following misconceptions: the pH is inversely related to harm and bases are not harmful; bubbles is a sign of chemical reaction or strength; acids and bases have their own particular colour or colour intensity (bases are coloured blue, acids are coloured pink and even different pH solutions have different colours); the molecules fight and combined, and phenolphthalein helps with neutralization; acids melt metals, acids are strong and bases are not strong; pH is a compound called phenolphthalein, a chemical reaction and a number related to intensity.

Bradley and Mosimege (1998) investigated whether student teachers at a university and a college of education hold any misconceptions about acids and bases. The following misconceptions were found: Aqueous solutions of all salts are neutral; there are misconceptions regarding conjugate bases; an indicator is paper used in laboratory when testing whether the acid is strong or weak; indicator neutralizes the acidity property of a solution to a more basic one. In this study, Acid-Base Concept Test was prepared considering these misconceptions. The students’ misconceptions in acid and base concepts were found through the use of Acid-Base Concept Test.

For better understanding and meaningful learning, there is a need for finding ways overcome misconceptions. One of the instructional methods can be used for this purpose is conceptual change approach. Many techniques based on the conceptual change approach help students to change their misconceptions. One of the most successful techniques to overcome students’ misconceptions is the conceptual change texts or refutational texts (Dole & Neiderhauser, 1990).

For the past decade, a considerable number of studies have been done in conceptual change in science education. The most well-known conceptual change theory was proposed by Posner. Posner et al (1982) proposed two types of conceptual change, assimilation and accommodation. Assimilation describes the process where students use existing concepts to deal with new phenomena and accommodation describes when the student must replace or reorganize his concepts.

Posner et al. (1982) (cited in Suping, 2003), provided no formal definition of conceptual change, but examples of what it entails were given. A student’s conceptual ecology is key to the conceptual change model because “without such concepts it is impossible for the learner to ask a question about the phenomenon, to know what could count as an answer to the question, or to distinguish relevant from irrelevant features of the phenomenon”.

In an attempt to clarify the concept of conceptual change, various theorists have offered competing views of the central process.

 To Vosniadou (2002), conceptual change is a process that enables students to synthesize models in their minds, beginning with their existing explanatory frameworks. This is conceived to be a gradual process that can result in a progression of mental models. Mortimer (1995) argues for what he calls a conceptual profile change because “it is possible to use different ways of thinking in different domains” and “the process of construction of meaning does not always happen though an accommodation of previous conceptual frameworks in the face of new events or objects, but may sometimes happen independently of previous conception”. Though their arguments differ, the view of Mortimer and Vosniadou are related and acknowledge the importance of prior knowledge to learning.

 Chi and Roscoe (2002) conceive of conceptual change as repair of misconceptions. Starting with naïve conceptions, students must identify their faulty conceptions and repair them. In this view, misconceptions are miscategorizations of concepts, so conceptual change is the reassignment of concepts to correct categories.

 Conceptual change to diSessa (2002) is the reorganization of diverse kinds of knowledge into complex systems in students’ minds. In this view, conceptual change is really about cognitively organizing fragmented naïve knowledge.

 Ivarsson, Schoultz, and Saljo (2002) take a more radical stance in that they think naïve conceptions do not serve a purpose in conceptual change because conceptual change is the appropriation of intellectual tools. In this view, conceptual change results from changes in the way that students use the tools in various contexts, and the change actually occurs at the societal level.

Posner et al. (1982) proposed four conditions necessary for conceptual change to occur:

  1. There must be dissatisfaction with existing conceptions. Dissatisfaction arises when learner loses faith in the capacity of current concept to solve problems. Anomalies are an important source of dissatisfaction. Asking students for explanations of familiar and discrepant events and debating alternative conceptions to activate their prior knowledge make them the more dissatisfied with their current concepts and the likely they may be ready to accommodate new ones.
  2. A new conception must be intelligible; this is that learner knows what it means and constructs a coherent representation of what a passage or theory is saying. If learner is not met the conditions, he or she internalizes the conception through rote memorization. Intelligible goes beyond simple understanding of word meaning. Analogies can serve to suggest new ideas and make them intelligible.
  3. A new conception must appear initially plausible: Plausible means that new concept is grounded in its consistency with other accepted concepts and be able to solve the same problems as previous concepts. The plausibility of new concept is dependent on intelligibility. If seeing the connection between analogy and target, learner believes the new concept is potentially true in the world. Posner et al (1982) suggest five ways in which a concept could be initially plausible;
  1. One finds it consistent with one’s metaphysical and epistemological beliefs.
  2. It is consistent with other theories or knowledge.
  3. It is consistent with past experience.
  4. One can create images for the conception, which match one’s sense of what the world is or could be like.
  5. The concept is capable of solving problems of which one is aware.
  1. A new concept should suggest the possibility of fruitful research program. This means that students show new approaching when they resolve problems and open up new areas of inquiry.

Teachers who accept these four conditions as necessary for conceptual change to occur are encouraged to take deliberate steps to create classroom interactions that produce these conditions. To become more effective in nurturing conceptual change, teachers should seek to understand students’ misconceptions so they can be addressed directly by instruction. Niaz, Aguilera, Maza, & Liendo (2002) (cited in Suping, 2003) have also concluded that if students are given the opportunity to argue and discuss their ideas, their “understanding can go beyond the simple regurgitation of experimental detail.” In this study, after determining the students’ misconceptions in acid and base concepts, the conceptual change texts were used in order to eliminate these misconceptions.


2.1. Design of the Study

In this study, Non-Equivalent Pretest-Posttest Control Group Design was used to evaluate students’ development. Experimental group was instructed by conceptual change texts oriented instruction (CCOI) and control group was instructed with traditionally designed chemistry instruction (TDCI).

2.2. Subjects of the Study

The sample of this study was 63 tenth grade students from two classes of a chemistry course at a high school. One of the classes was assigned as a control group instructed by TDCI and another was assigned as an experimental group instructed by CCOI.

2.3. Instrument

In order to measure the students’ understanding of acid-base concepts, Acid-Base Concepts Test (ABCT) was used. This test was developed by the researchers. It consisted of 25 multiple-choice questions. Content of the test was determined from the lecture materials and some chemistry books which cover the same learning material included in conceptual change text. Each question had one correct answer and four distracters. Each item in the Acid-Base Concepts Test was examined by a group of classroom teachers and experts in science education and chemistry for the appropriateness of the items and the content validation. The reliability of the test was found 0.74. This test was given to students in both groups as a pre-test to control students’ understanding of acid-base chemistry at the beginning of instruction. It was also given to both groups as a post-test to determine the effects of treatment on understanding of acid-base concept.

2.4. Treatment

In the study, there were two groups of students: Experimental group and control group. The topics related to acid-base chemistry were covered as a part of the regular classroom curriculum in the chemistry course. The classroom instruction was three 40 minute sessions per week. In the control group, the students were instructed only with traditionally designed chemistry instruction. During the classroom instruction, the teacher used lecture and discussion methods and solved algorithmic problems to teach acid-base concepts. Also, the students were provided with the worksheets. Each worksheet included mathematical and conceptual chemistry questions. The teacher acted as a facilitator and answered some questions and make suggestions when needed. Worksheets were corrected and scored and the students reviewed their responses after correction.

Students in the experimental group worked with conceptual change texts. Conceptual change texts were prepared by the researchers. They identified common misconceptions about subject matter and directly informed students that may possess such kind of misconceptions. They activated students’ misconceptions by presenting simple qualitative examples that allow the misconceptions to be used to make a prediction about the situation and they presented the evidence that typical misconceptions are incorrect and provided a scientifically correct explanation of the situation. Each part of conceptual change text was distributed to students in class hours and students were instructed to read texts carefully. After they read texts, teacher explained students’ misconceptions, causes of these misconceptions, why these conceptions were incorrect and scientifically correct situation within a discussion environment.


In order to find out students’ previous knowledge about the acid-base concepts ABCT was given to students before the treatment. The analysis showed that there was no significant difference between CCOI group and TDCI group in terms of acid-base concept achievement (t = 0.279, p > 0.05). To answer the question posed by hypothesis stating that there is no statistically significant difference between the mean scores of the student taught with traditionally designed chemistry instruction (TDCI) and those taught with conceptual change oriented instruction (CCOI) with respect to understanding of acid-base concepts. The analysis results showed that the post-test mean scores of CCOI group and TDCI group with respect to understanding of acid-base concepts were significantly different (t = 4.48, p < 0.05). CCOI group scored significantly higher than the TDCI group (The mean score of CCOI group = 51.13; the mean score of TDCI group = 50.12). Questions related to find the relationship between pH/pOH and [H+]/[OH-] were confused by the students in TDCI group. They used these terms by mechanical or technical sense without understanding of the concept. 38% of students in TDCI group answered questions correctly, whereas 87% of students in CCOI group answered questions correctly. A similar difference between CCOI group and TDCI group was seen for the question that a salt contains neither hydrogen nor a hydroxyl group; its solution cannot contain hydronium or hydroxide. After treatment 68% of students in CCOI group did it correctly while 25% of students in TDCI group did correctly.