CHAPTER 2 LITERATURE REVIEW AND MOTIVATION FOR THE STUDY
2.5 A SUITABLE TOPIC FOR REVIEW
with no explicit assessment of research quality (Bennett et al., 2005a). Moreover, traditional reviews may be biased towards larger studies published in top journals, while neglecting smaller but important studies (Torgerson, 2003). The ‘streamlined’ systematic review process which Bennett et al. (2005a) advocate is suitable for a narrowly focused research question to be answered through secondary analysis of published research reports. It has rigorous and replicable strategies for searching, screening and mapping these reported studies. Adapted from medical research, it has proved effective in science education (Bennett, Campbell, Hogarth &
Lubben, 2005b; Lubben et al., 2005; Bennett et al., 2007) but it seems, at the time of writing, that it has not been used for research into student conceptions.
2.4.6 Propositional knowledge in conceptions research
When Erikson (2000, p 287) advocated further research on domains where knowledge of student conceptual difficulties was lacking, he emphasised a need to include “explicit orientating frameworks”. Similarly, in their 1995 review article, Garnett et al. advocated having a list of “conceptual and propositional knowledge” (p 83) as a starting point for further research into misconceptions. Describing student conceptual difficulties as Limited or Inappropriate Propositional Hierarchy (LIPH), as suggested by Novak and Gowan (1984), shows that these propositional statements are essential; how else does a researcher adjudicate what is missing or inappropriate? I anticipated needing such a set of propositional knowledge when formulating Research sub-questions 2c, 3c and 4c. Treagust (1988; 1995) outlines a method for deriving a coherent set of propositional statements from expert knowledge. A further aspect of Treagust’s method includes developing concept maps to establish coherency or internal validity of propositions within a topic. Both aspects are important pedagogic knowledge for teachers in a discipline.
2.5 A SUITABLE TOPIC FOR REVIEW
highlights the pervasiveness of acid-base chemistry in other topics such as the nature of inorganic oxides of metals and non-metals, or the acidity of phenols and carboxylic acids in organic chemistry. Furthermore, introductory college biology may include acid-base chemistry in cellular processes, such as protein and nucleic acid denaturising, enzyme activity, oxygen and carbon dioxide transport (Rhodes, 2006; Watters & Watters, 2006). Despite this stated importance, recent general reviews report very few student difficulties in the topic of acid-base chemistry; for example, Kind (2004) reported five, contrasting with 20 reported for each of electrochemistry and particulate nature of matter, while Garnett et al. (1995) reported nothing specifically on the chemistry of acids and bases. Currently, the literature contains no specific review on the topic of acid-base chemistry.
2.5.2 The potential of acid-base chemistry for misconceptions and difficulties
It could be argued that acid-base chemistry does not yield many difficulties, but this is hardly true in light of teachers’, students’ and educationists’ ideas of the complexity of acid-base chemistry as follows. In the United Kingdom, senior chemistry teachers rated the topic as the third most difficult to teach (Ratcliffe, 2002). Among Swedish chemistry teachers, none rated the topic as their favourite; they anticipated mostly mathematical rather than conceptual difficulties (Drechsler & Schmidt, 2005a). Some students also dislike the topic. Specifically, Tarr and Norwell (1985) describe feelings of fear, hopelessness and intolerance among medical students who often resorted to rote and algorithmic learning: “Nothing, it seems, is as universally misunderstood and difficult to convey as the concepts surrounding the biological responses to hydrogen ions” (p 14). New Zealand secondary school students thought acid-base chemistry was a difficult topic, especially where ionic equations are needed. They rated their performance as third poorest in 50 topics (Burns, 1982). Similarly, Wisconsin students ranked pH as the fifth most difficult topic in chemistry (Finley et al., 1982). Ratcliffe’s (2002) report suggested that students held very different views to their teachers (above). These students thought there were 15 other chemistry topics more difficult to learn than acids and bases. In the same vein, Furió-Más et al. (2005) noted Spanish students’ belief that it was a simple topic, even boring. Swedish teachers, mentioned above, also thought it was superficial, offering little further extension beyond students’ experience in junior secondary school (Drechsler & Schmidt, 2005a). However, as noted earlier (see Section 2.4.4), teachers tend to underestimate the impact of student conceptual difficulties (Agung & Schwartz, 2007). In summary, the topic is recognised as being important, but teachers appear to dislike the topic but for different reasons,
seeing it either as undemanding or presenting mostly mathematical difficulties. Students’
opinions vary; some rank its difficulty level high and others low.
Adding to the surveys above, research suggests that the high cognitive demands associated with studying acid-base chemistry will probably yield conceptual difficulties. To be specific, Herron (1975) anticipated that students who do not reason abstractly would struggle to “conceive an acid as a proton donor or electron pair acceptor” although they should not have trouble conceiving “an acid as any substance that will turn litmus red”. This reflects Johnstone’s (e.g.
2002) contention that many difficulties in learning chemistry arise from different representations in chemistry; specifically the macroscopic, molecular and symbolic.
Furthermore, acid-base chemistry involves several distinct models (e.g. Kolb, 1978, Oversby, 2000a) and student difficulties in such situations have been recorded (e.g. Justi & Gilbert, 1999). Specifically, according to Nakhleh and Krajcik (1994), the topic requires a deep understanding of atoms, molecules, ions and chemical reactions, and on a similar note, Johnstone (2002, p 13) contends: “Many of the wrong ideas that students have start with ions and salts.” It follows that experts in chemistry education research anticipate students having difficulties in the acid-base topic.
Different categories of concepts might be assimilated in differing ways according to a student cognitive level. In this regard, Wilson (1998) found that weaker students tended to use matter concepts (such as acid or base) around which to organise their knowledge, while more advanced students were able to use process concepts (such as ionization) for the nodes in their concept maps. As a result, she suggests that teachers use the first, more concrete, category as an organisational framework for novice learners; the second, more abstract, category being more suitable for advanced students. This aspect suggested there could be different categories of difficulties according to the central organising idea – namely chemical species or processes.
Furthermore many reports concerning student difficulties in interpreting representations used in chemistry, such as scientific terms (see Section 2.3.2), mathematical expressions (e.g. Potgieter et al., 2008) or chemical symbols (e.g. Yarroch, 1985; Treagust & Mamiala, 2003) suggest that difficulties with representations can be expected to pervade all aspects of chemistry.
2.5.3 Acid-base presentation in textbooks.
Textbook inaccuracies with acid-base chemistry have also been reported (e.g. Carr, 1984).
Specifically, Loeffler (1989, p 929) pointed out: “the entire field of acid/base chemistry is filled
with ambiguous or seemingly inappropriate word usage and symbolism”. Recent content analyses of the acid-base topic carried out on textbooks published in the United Sates (Erduran, 1996; de Vos & Pilot, 2001), the United Kingdom (Oversby, 2000a), Spain (Furió-Más et al., 2005), Greece (Kousathana et al., 2005) and Sweden (Drechsler & Schmidt, 2005a; Drechsler &
van Driel, in press) indicate a persistent and widespread problem. All these studies report instances of hybrid or mixed acid-base models and corresponding lack of distinction between applicable contexts for the models, resulting in an incoherent presentation for readers.
Moreover, textbooks are sometimes contradictory; to be specific, different definitions of acids are given almost contiguously without differentiating contexts (Evans & Lewis, 1998), while textbook explanations of relative strength of acids in water have been described as “nebulous”
and sometimes inconsistent with explanations, such as strength of chemical bonds given later in a book (Moran, 2006, p 800). Formal instruction has already been implicated in student conceptual difficulties (see Section 2.3.4) and, clearly, textbooks could be an important cause of student conceptual difficulties in this area of chemistry. Accordingly, a need for a different source of propositional knowledge in the topic was anticipated in the current research.