CHAPTER 2 LITERATURE REVIEW AND MOTIVATION FOR THE STUDY
2.3 SOURCES OF STUDENT CONCEPTUAL DIFFICULTIES
Numerous causes have been put forward for student conceptions which are contrary to accepted science. Wandersee et al. (1994) warn that tracing the origins of alternative conceptions is largely speculative, as each learner is individual. Nevertheless, the universality of these conceptions among different cultures and ages suggests several common experiences that can cause difficulties. These include the nature of science (and more particularly chemistry) and the language of science, informal and formal instruction, as well as sources within a student, which are discussed below.
2.3.1 The Nature of Science
Students may misunderstand the nature of science (Kousathana et al., 2005). In this way, they may consider scientific conceptions or theories as “a kind of privileged truth” instead of being viable within a historical or practical context (von Glasersfeld, 1995b, p 15). Furthermore, students sometimes believe scientific models have direct correspondence with reality (Oversby, 2000a; Talanquer, 2006). They could be confused between models (Carr, 1984; Hawkes, 1992, Drechsler & Schmidt, 2005b)) and may even attempt to integrate several distinct models into
one composite model (Justi, 2000), as do many textbooks (Justi & Gilbert, 1999; 2002a).
Teaching a simplified curriculum model may itself introduce difficulties (Glynn et al., 1991).
2.3.2 The Language of Science
The language of science also presents difficulties (Özmen, 2004). Scientific texts often introduce more new vocabulary words per page than do foreign language texts (Glynn et al., 1991). Non-technical words like ‘pungent’ or ‘aqueous’ or ‘excess’ may also be beyond a school pupil’s ordinary vocabulary or not understood within a science context (Cassells &
Johnstone, 1983; Johnstone, 1991). Further language difficulties may arise when students superimpose their everyday word associations onto scientific terms with restricted meanings (Pines & West, 1986; Chiu, 2007). Another difficulty may arise when the scientific meaning for a concept label has changed historically, yet the label still invokes the original concept for students (Schmidt & Volke, 2003). Kuhn (1970) argues that this confusion is also found among scientists when a paradigm shift occurs. When students are not learning in their mother tongue, as happens for many in South Africa, these difficulties may be compounded (Moji, 1998). In this matter, Clerk and Rutherford (2000) investigated so called wrong answers to multiple- choice probes published by other authors. They showed these answers had been too readily ascribed to misconceptions (as incorrectly assimilated mental models) rather than language difficulties. They differentiate clearly between these two categories because each requires specific remedial strategies.
Nevertheless, while poor understanding of the language of science may in itself not be a misconception, it can give rise to inappropriate mental models. Herron (1979) believes that when chemistry teachers themselves misuse or permit misuse of scientific language they could contribute to student conceptual difficulties; for instance, allowing students to refer to all of H2, H+ and H simply as ‘hydrogen’ suggests erroneously that there is no difference between molecules, ions and atoms. Moreover, knowing the distinctive and limited meanings for explicit terms that are appropriate to specific situations is part of acculturation into chemistry (Oversby, 2000a). Language is one essential level on which to understand and communicate chemistry (Laing, 1999). This language aspect, together with the argument about concept labels from the previous section, is relevant in three ways for the current project; it necessitated a careful analysis of the language used in research instruments and claims of misconceptions but it also informed one of the categories of difficulties.
2.3.3 The Nature of Chemistry
Several levels of thinking characterize, and are the very strength of, modern chemistry as an academic endeavour. These are the macroscopic or operational level, the sub-microscopic or particle level, and then the symbolic level used to describe and explain phenomena. For centuries chemistry was understood only through macroscopic tangible experiences of phenomena. Then by the mid 19th century, symbols, formulae and equations were normal representations among chemists. Much more recently – since 1950 (Laing, 1999) – atoms, electrons and bonding became the dominant way of thinking. Expert chemists move fluently, and sometimes tacitly, between the levels of representation (Johnstone, 1982). By contrast, students have trouble navigating through and integrating the levels (for example Ben-Zvi et al., 1986; Gabel, 1993; Johnstone, 1993; Chiu 2007; Drechsler & Schmidt, 2005b). Johnstone (2002, p11) argues that a reason for these difficulties lies in overload of working memory, which prevents a novice from simultaneously receiving, processing and integrating information in the “triple layer sandwich”. Furthermore, an overloaded chemistry curriculum allows students little time to make connections between representational levels, which leaves their knowledge compartmentalized. It then appears that attempting to load too many simultaneous levels of thinking onto students hinders meaningful learning, with resultant conceptual difficulties (Gabel, 1993; Nelson, 2003).
Since 1960, many chemistry courses have logically started with elements and atoms, whereas chemistry educators have continually argued against the psychological structure of such an inverted highly abstract curriculum (for example Novik & Nussbaum; 1978; Vogelazang, 1987;
Gabel, 1989; Johnstone, 1991; Laing 1999; Solomonidou & Stavridou, 2000; Nelson, 2002).
Furthermore, Laing (1999) and Johnstone (1991) both maintain that much useful and interesting introductory chemistry can be taught that is both tangible and non-abstract.
Over and above the inherent difficulty of the multi-level nature of chemistry, teachers appear to be unaware of, or may even compound, the problem (Gabel, 1999). In this matter, Loeffler (1989) contends that traditional teaching involves “ambiguously skipping back and forth with an imprecise and often incorrect usage of confusing terms” (p 930). He gives examples of mature chemists frequently using the same word or formula to denote both species (atom, ion or molecule) and substance, assuming that students could infer the intended meaning from the context. Consequently, students, experience difficulties with each representational level, in addition to difficulties in distinguishing, but at the same time linking, these three systems. The
difference between knowledge of experts (possibly tacit) and novices forms a large part of the research in this current project.
2.3.4 The Nature of Instruction
Student conceptions are influenced informally by both the media and their peers (Botton, 1995;
Chiu, 2007). Solomon (1993a, p 9) describes a “cognitive tension” between cultural and scientific knowledge causing emotional reactions to mask scientific thinking, so that “...what is sensational, or comfortably agreeable, survives at the expense of accuracy.” Even a well- educated lay public associates the word chemical with manufactured materials, possibly toxic or carcinogenic (Evans, 2006). It is heartening that Longden et al. (1991) report an apparent decrease in this influence as students are exposed to more science instruction.
Formal instruction may cause its own misconceptions. These could arise from teachers’
inadequate content knowledge or through inappropriate teaching strategies, or textbooks themselves might foster misconceptions. Teachers’ own misconceptions may be transmitted to students (Blosser 1987; Chiu, 2007). Specifically, Kruse and Roehrig (2005) found parallels between scientifically unacceptable conceptions identified among students and their teachers, which were more prevalent among teachers without a chemistry major qualification. The authors concluded that these teachers probably transmitted their own misconceptions to students or covered only superficially content where they lacked confidence. The research also showed that these teachers thought chemistry required much intuitive knowledge, possibly due to their not having experts’ tacit way of moving confidently between representation systems in chemistry.
Many chemistry concepts (for example oxidizing agent or proton-donors) are in fact non- intuitive and so students are hardly likely to develop any conceptions (alternative or acceptable) on their own initiative. Taber (2001a, p 128) elaborates (with his own italics): “it is important to note that most alternative conceptions in chemistry do not derive from the learner’s unschooled experience of the world.” In this way he sees alternative ideas, not as naïve or intuitive conceptions such as frequently found in physics, but rather those derived from a student’s prior formal learning experiences. Accordingly, he argues that most difficulties in learning chemistry have pedagogic and epistemic causes. Rather than laying blame, Taber asserts that these are opportunities to make things better for students. The aim of this project is to contribute to such a solution.
A connection exists between information available to students and alternative conceptions they might develop; one instance could be a limited range of examples given to students. In particular, if they have studied only strong acids, they might assume that all acids behave similarly (Schmidt, 1997). Another instance could be allowing student conceptions to develop informally, rather than through carefully planned instruction; consequently students may not distinguish between two similar but different concepts (Herron; 1996; Taber, 2001a). As discussed earlier, Herron (1996) suggests that before teaching a topic, teachers first undertake a conceptual analysis, which includes finding examples and non-examples to show the extent and limitations of a concept.
There could also be a mismatch between students’ prior learning and teachers’ assumptions about students’ existing ideas. Students’ pre-existing conceptual links are critical for meaningful learning so conceptual problems may easily arise when teachers falsely assume that a student understands core concepts and make no provision for this knowledge to be constructed (Tullberg, 1994). Without tacit knowledge which experts use to weave their way through different representational models in chemistry, students could well have limited or inadequate conceptions. Identifying this tacit knowledge as propositions (see Section 2.1.2) is the focus of Research sub-questions 2c, 3c and 4c.
Textbooks may also be a source of misconceptions due to a mismatch between scientifically accurate models or theories and those that are appropriate to the cognitive development of younger students. It is impractical to teach a sophisticated expert view to young children, but presenting a simpler, more easily comprehended theory (as a curriculum model, see Section 2.1.3) may result in actually teaching misconceptions. If these are not subsequently straightened out they may be carried through as scientific illiteracy (Glynn et al., 1991). Over- simplistic textbooks which introduce errors are a widespread problem shown, for example, in research from physics (Carvalho & Sampaio, 2006), biology (Clifford, 2002) and chemistry (Sanger & Greenbowe, 1999; Smith & Jacobs, 2003). The problem is found among elementary textbooks, as shown by Barrow (2000), and those for university undergraduates, as shown by Sawyer (2005). In particular, textbook presentation of scientific models has been widely criticized as confusing for students (e.g. Carr, 1984; Loeffler, 1989; Oversby, 2000a; de Vos &
Pilot; 2001; Drechsler & Schmidt, 2005a; Justi & Gilbert, 1999, Gilbert et al., 2000). More specifically, Andersson (1986) recommends that textbooks emphasise the provisional nature, as
well as explanatory and predictive roles of models, while making clear distinctions between a model and the real world: “If our ideas about atoms are correct what should happen here?” (p 561). In both this review article and another in 1990, Andersson emphasises careful choice of words; for example, water is frequently described as consisting of oxygen and hydrogen conveying an idea that it is a mixture, rather than being described as a compound of oxygen and hydrogen. Accordingly, in the current project, propositional knowledge which was put forward, needed to be carefully verified, to make it compatible with expert opinion.
2.3.5 The nature of students
According to Brown et al. (1989) conceptual knowledge cannot be abstracted from its context, that is, it is situated within the culture in which learning takes place. As this work is situated within a social constructivist paradigm (Novak, 2002), the nature of students is considered to influence their learning. Three aspects are considered here. Students’ gender may affect the type of instruction they need in order to counter misconceptions as, for instance, Chiu’s (2007) evidence for gender differences in conceptual understanding of chemistry among Taiwanese students. In other studies, appropriate interventions enabled females, who initially performed worse than males, to subsequently perform at the same conceptual level as their male peers.
These interventions required and assisted students to visualize chemical reactions at particulate levels (Bunce, 2001; Yezierski & Birk, 2006). This suggests that females need specific instruction in using visual models.
Students also tend to compartmentalize their knowledge – using different aspects according to different situations; for instance, Taber (2001a) gives numerous examples where students do not apply electrostatic principles learned in physics to chemical bonding. Students also appear to make little attempt to reconcile everyday and science knowledge, retaining personal theories and models but insulating them for protection from discrepancies observed in science lessons.
Personal theories are used out of class while scientific theories are presented for the teacher.
However, initial conceptions may be retained but become wrapped up in more and more scientific jargon as students progress, so they are difficult to detect through factual recall tests (Glynn et al., 1991). Lewis and Linn (1994) reported this separation of everyday and science knowledge as occurring among adolescents, adults and even professional scientists. Everyday knowledge as general principles, or p-prims, which students use to predict behaviour of the natural world, may itself not be integrated into a coherent whole, remaining as knowledge in pieces (diSessa, 1998), used according to context.
Some students may have difficulty applying rules of logical reasoning. Herron (1996) points out the commonality of proportional relationships in concepts that cause difficulties, for example, density, stoichiometry, acceleration and rate of reaction. Following chains of formal hypothetico-deductive (logical inference such as if... then ...) or probabilistic reasoning have also been put forward as essential reasoning skills for success in science, but which are often lacking (Herron, 1975; Cantu & Herron, 1978; Lawson & Thompson, 1988). The fraction of students identified as having developed such abilities is small: 21% of a biology class with an average age of 13 years (Lawson & Thompson, 1988), 40% of a high school introductory chemistry course (Goodstein & Howe 1978) and 20% of biology students at a community college (Lawson et al., 1993). Instead of formal reasoning, students tend to use their own intuitive reasoning rules in mathematics and science (Stavy & Tiroch, 2000). Talanquer (2006) presents a model for interpreting published chemistry misconceptions in terms of students’
erroneous ideas which appear to them as ‘common sense’ and which they use in an attempt to reduce cognitive overload. It is important to identify such troublesome concepts in order to provide appropriate support for such students.