Constructivism has been one of the most influential themes in science teaching and learning since the 1980s. Science educators attempted to find out students’ ideas about different science concepts as considering students’ ideas when designing instruction has become crucial for subsequent learning. The results of these studies highlighted the resistance of preconceptions to change and their potential in affecting students’ future learning. Students’ ideas expected to be highly influential over their learning process especially when they have roots in many science concepts.

Conservation of mass is such a concept as it has relationships with matter and all physical and chemical changes it undergoes. Thereby, the concept of conservation of mass has received researchers’ attention before 1980s. The initial work on the conservation of mass was conducted by Piaget&Inhelder (1974). They examined students’ predictions of mass on the process of dissolving. They found that students didn’t conserve mass of sugar after dissolving due to their perceptual experience. They interpreted the failure of students’ mass predictions as lack of logical operations whereas Stavy (1990) opposed to this general reasoning skill interpretation. She studied student ideas on a range of physical changes such as melting, evaporation and dissolving. She found that students pass some conservation tasks while they fail the others. Thus, she didn’t question students’ logical operation. Rather, she suggested that an alternative system of knowledge affects students’ understanding about conservation.

Several researchers studied students’ understanding of the conservation of mass. These studies focused on conservation of mass in changes such as combustion in a closed-system (Driver et al., 1984;BouJaoude, 1991), dissolving (Anderson, 1984;Stavy, 1990), rusting (Driver, 1985), sublimation (Mayer, 2011), gases (Furio et al., 1987;De Berg, 1995), precipitation reactions (Ramsden, 1997;Barker&Millar, 1999), closed and open-system chemical reactions (Özmen&Ayas, 2003). The common finding was the difficulty experienced by students in applying the conservation of mass to changes in matter regardless of their educational or achievement level. Finding out the reasons lie under this difficulty is likely help educators in designing more effective teaching schemes. 

These studies basically focused on students’ understanding about conservation of mass on two or three concepts, if not only one. There’s a need for research to examine students’ ideas about conservation of mass in various ways of physical and chemical changes. Thus, it might be possible to uncover the knowledge that affects students’ ability to conserve mass and whether this knowledge is domain-specific in nature or involves general reasoning skills. This study aimed to investigate Turkish secondary students’ ideas about conservation of mass in a range of physical and chemical changes. It also aims to find out students’ ideas about the relationship between mass-heat, mass-chemical bond. The research questions to be addressed in the study can be stated as follows;

1.      to investigate 9^th grade students’ mass predictions on various physical and chemical changes  

2.      to uncover the underlying reasoning behind students’ mass predictions

3.      to explore the consistency of reasoning used in students’ conservation of mass explanations across a range of events involving physical and chemical changes

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