Evaluation of eleventh grade Turkish pupils’ comprehension of general chemistry concepts

The objective of this study is twofold: to evaluate the extent of comprehension of eleventh grade Turkish students on various general chemistry concepts that in turn provides information related to the chemistry concepts which are easier and harder for students to comprehend, and to investigate the effect of gender and last semester chemistry course grade on pupils’ comprehension of chemistry concepts. The analyses of data suggest that the extent of comprehension of eleventh grade students on various general chemistry concepts is not in conformity with the extent as intended. The percentages of correct responses of students on the CCI ranged from 4.5 % to 75.0 %. Among items, only seven of them had correct response rate within the 50-75 % interval, eight within the 30-50 % interval, and the remaining six items located in the interval of 4-30 %. Investigating items within aforementioned percentage intervals enables to establish the concepts that are easier and harder for students to comprehend which is the concern within the scope of this study.

The highest percentage of correct responses was shared by items 12 and 13 which are paired in nature. Results indicated that most of the students (75 %) do not have problems related to mass conservation during phase changes of matters. However, the remaining 25 % of respondents demonstrated common alternative conceptions such as, “Mass would be less or more as matters change phase”, and “A gas weighs less than a solid”. Actually, the number of students who marked “Mass would be less” (about 18 %) is much greater than the students who signed “Mass would be more” (about 7 %) which is a situation that resulted from students’ alternative conception of “A gas weighs less than a solid” (almost 10 %). This instance verifies that alternative conceptions hinder students’ further learning (Jones & Beeth, 1995). These alternative conceptions are analogous to the results of studies reported in related literature (Stavy 1988, 1990; Mas et al. 1987; Lee et al. 1993). Seventy percent of respondents expressed the contents of bubbles in boiling water (Item 2) as “Water vapor”, though 24 % believed that “The oxygen and hydrogen gases” are the nature of bubbles in boiling water, which is an alternative conception also reported by the related literature (Osborne & Cosgrove, 1983; Goodwin, 2000; Costu et al., 2007; Bar & Travis, 1991). About 68 % of pupils clarified conservation of mass during dissolution but 24 % of them gave clues about the alternative conception “Mass of solution takes a value between mass of solvent and total masses of solute and solvent” (Item 4). This result marks that students may have various alternate conceptions about dissolution process such as, “Solvent is the major component of a solution”, “Dissolved solute has no weight since it disappears”, and “Solvent loses weight during dissolution” (Çalik & Ayas, 2007; Ebenezer & Erickson, 1996; Abraham et al., 1994; Prieto et al., 1989; Uzuntiryaki & Geban, 2005). Item 15 was related to heat and temperature concepts and correct reponse rate was 59 %. Assembling concepts of all seven items within the interval of 50-75 may give chance to declare that; students comprehend “Phase changes, conservation of mass, heat and temperature” concepts easier than other general chemistry concepts included within the CCI.

On the other hand, the poorest percentage belonged to item 5 which investigated chemical formulas and equations. Almost 95 % of respondents selected scientifically incorrect responses that can be commented as students are unable to comprehend conservation of atoms in chemical reactions. This result is similar with the results of Mulford & Robinson (2002) in which the lowest percentage of correct response was also the 5th question. This circumstance points out that some alternative conceptions are not culture bound as reported in the literature (e.g. Çalik & Ayas, 2005). Students believed that “Not only total mass and atoms were conserved but also the number of molecules were conserved during a chemical reaction” (nearly 31 %), which indicates confusion between molecules and atoms (Item 1). These results indicate the difficulty of students in understanding sub-microscopic and symbolic representations of chemistry concepts. Moreover, students were also found to have difficulties concerning concentration behaviors of saturated solutions as water evaporates (Items 19 and 20) and macroscopic versus atomic and molecular properties (Item 21). Gathering concepts of all six items that fall into the interval of 4-30 may be helpful for deducing that; students’ comprehension of “Chemical formulas and equations, macroscopic versus atomic and molecular properties, solutions, chemical reactions, properties of atoms” concepts is harder than other general chemistry concepts included within the CCI.

Results of this study are consistent with the results of Mulford and Robinson (2002) and Boz and Uzuntiryaki (2005) in which freshmen entering students and pre-service science teachers were examined, respectively. Mulford and Robinson (2002) reported difficult chemistry concepts for respondents as “atoms and molecules, microscopic behaviour, heat and temperature, chemical formulas, gases, and other qualitative concepts” (p. 742). Boz and Uzuntiryaki (2005), similarly, reported the hardest chemistry concepts for pre-service teachers as; solutions, chemical formulas, and macroscopic versus microscopic properties. To conclude, freshmen entering students, pre-service science teachers and eleventh grade students have common alternative conceptions as stated in the related literature (Haidar & Abraham, 1991; Garnett & Treagust, 1992).

Other conclusion of the study is that there is no significant effect of gender and chemistry course grades on eleventh grade Turkish pupils’ comprehension of general chemistry concepts.