Conclusion and implications for teaching
In the literature, Liu and Lesniak (2006) state that there is no clear conceptual leap between different grade levels in conceptual progression, that is, there is tremendous overlap in conceptions among students of different grades. According to Liu and Lesniak (2005), matter concept development in children from elementary to high school undergoes five overlapping waves. The first wave involves developing informal ideas on matter such as properties and changes involving water and air and may occur by grade 3 or 4. The second wave occurs by grade 7 when students develop understanding of the aspect on matter conservation. The third wave is indicated by understanding physical and chemical properties and change by grade 8 and 12 general students. The fourth wave involves structural and composition aspect of the matter. And the last wave involves explaining and predicting matter and changes using bonding theories. Treagust, Chittleborough and Mamiala (2003) state that only at the last level are students fluent in representing and coordinating matter and changes at the macroscopic, symbolic, and microscopic levels. For this reason, it may be unreasonable to expect conceptual leap between the 4th, 5th, and 6th grade in this study.
A common misconception among the students was the attribution of macroscopic properties to particles. For example, majority of the students in all grades think that the size and number of particles will change during phase changes. The attribution by students of macroscopic properties of substances to the particles has also been stated in the literature (Boz, 2006; Griffiths and Preston, 1992; Kokkotas et al., 1998). Gabel, Samuel and Hunn (1987) state that misconceptions and these lack of understanding of the particulate nature of matter on the part of chemistry students may be related to their lack of formal operational development or to their poor visualization ability. They also think that it is more likely due to their lack of differentiation of concepts such as solids, liquids, gases elements, compounds, substances, mixtures, solutions, and to the lack of instruction in which these terms are related to the particulate nature of matter.
According to literature, chemistry may be understood at three different levels, namely, the macroscopic, microscopic and symbolic levels (Raviola, 2001). In order to provide a sufficient understanding of a concept, students need to understand the relationship among these levels. But, it is also known that at the present time most chemistry courses are taught at the symbolic level with little emphasis on the microscopic and the macroscopic levels and insufficient connections are made between the three levels and the information remains compartmentalized in the long-term memories of students (Gabel, 1993). This causes insufficient understanding of concepts by the students. Therefore, teachers need to emphasize the transitions between the symbolic, macroscopic, and microscopic worlds so that students will develop their own mental models of particulate nature of matter on these three levels (Gabel, 1993). And also, teachers should also be equipped with the necessary capabilities of continuously identifying their own students’ conceptions and implementing teaching approaches that promote conceptual understanding among their students. Researches indicate that students’ difficulties and misconceptions in learning science concepts are due to in part to the teachers’ lack of knowledge regarding students’ prior understanding and knowledge of concepts under study (Krishnan and Howe, 1994). One of the most fruitful outcomes of the studies on students’ misconceptions is to alert teachers to students’ difficulties in conceptualizing science knowledge and suggest more effective strategies for improving classroom instruction.
Although some efforts have to be made to get better students’ understandings, the position of the particulate nature of matter in curriculum should also be discussed. According to Snir, Smith and Raz (2003) middle school students are ready to deal with important epistemological issues about models when being introduced to the particulate model of matter, but it is not profitable to engage them with these issues until they have developed a sound macroscopic understanding of matter. And also, introducing the particulate theory in elementary and middle schools may not be effective as has been found in a number of studies (Holgersson and Lofgren, 2004; Nieswandt, 2001). Moving this idea, it should be discussed how detailed the particulate nature of matter is taught in primary grades.
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