Quikmica

CHEMISTRY EDUCATION: RESEARCH AND PRACTICE

RESEARCH REPORT (EMPIRICAL STUDY)

2003, Vol. 4, No. 3, pp. 279-290

Concepts

Haluk ÖZMEN and Alipaşa AYAS Karadeniz Technical University, Fatih Faculty of Education, Department of Science Education

STUDENTS’ DIFFICULTIES IN UNDERSTANDING OF THE CONSERVATION OF MATTER IN OPEN AND CLOSED-SYSTEM CHEMICAL REACTIONS
Received 28 January 2003; infinal form/accepted 7 April 2003
ABSTRACT: The law of conservation of matter is a cornerstone in the development and advancement of modern chemistry. With this idea in mind, a test of four items was designed and used to determine students’ understanding about the conservation of matter in open and closed-system chemical reactions. The test was administered to 150 lycee-2 (grade 10; age 15-16)students after they studied the unit on chemical reactions. The analysis of the collected data revealed that students had some misconceptions. One of the most common misconception encountered was that “the total mass increases in a precipitation reaction because the precipitate produced is solid and it is heavier than a liquid.” Another misconception in parallel to the previous one was that “when achemical combustion happens in a closed system, the total mass decreases.” [Chem. Educ. Res. Pract.: 2003, 4, 279-290] KEY WORDS: secondary education; misconceptions; conservation of matter; chemical reactions; open-system chemical reactions; closed-system chemical reactions

INTRODUCTION The science education literature contains several studies of students’ understanding of scientificphenomena. These studies have revealed that students bring to instruction views and explanations of natural phenomena that differ from the views held by scientists (Osborne, 1982). Students’ preconceptions are not only quite different from those generally accepted in science, but also they are quite resistant to ordinary classroom teaching (Stavy, 1991). Such views of the world held by children are notsimply isolated ideas but form conceptual structures that provide a coherent understanding of the world from the child’s point of view (Gilbert et al., 1982; Hackling & Garnett, 1985). In recent years, there has been an increasing interest to determine students’ alternative views about science concepts and scientific events. These alternative views have been called in the literature common senseunderstanding (Hills, 1983), alternative frameworks (Driver, 1981), alternative conceptions (Driver & Easley, 1978; Gilbert & Swift, 1985), preconceptions (Novak, 1977; Hashweh, 1988), common alternative science conceptions (Gonzalez, 1997), prescientific conceptions (Good, 1991) or misconceptions (Helm, 1980; Hewson & Hewson, 1984, Lawson & Thompson, 1988; Treagust, 1988; Nakhleh, 1992). In thisstudy, the term misconception refers to students’ ideas which are different from those generally accepted by scientists. Within the domain of chemistry, surveys have revealed that the topics of chemical equilibrium, the mole, oxidation-reduction, reaction stoichiometry, chemical bonding and chemical reactions give learners most difficulty (Finley et al., 1982; Hackling & Garnett,

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1985). Chemistry is a science whose primary purpose is the description and explanation of chemical changes (Hesse & Anderson, 1992). Since the concept of chemical reaction is considered to be an important objective of chemistry teaching, teachers should be made aware of students’ difficulties in this area. The scientific understanding and applying of the conservation of mass in chemicalreactions is problematical for many students. This concept is a central theme in the program of Junior High School (14-15 years old pupils), and also a prerequisite for the subsequent understanding of chemistry. From a scientific point of view, the understanding of the mass conservation principle, as well as the knowledge of the general theory of chemical reactions, is indispensable for the whole...