The aspects of physical and chemical changes can make students experience some difficulties while distinguishing between these processes. The main misconceptions associated with these types of changes are the following ones: chemical changes are determined when unusual alterations in substances are observed; in contrast to physical changes, chemical changes are associated with alterations in masses; in contrast to reversible physical changes, chemical changes are viewed as irreversible in their nature (Driver, Rushworth, Squires, & Wood-Robinson, 2005).
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Thus, students are inclined to associate such physical changes as alterations in colors and masses with chemical processes, and instructors need to pay much attention to teaching students how to recognize physical and chemical processes and changes in order to avoid such mistakes. Furthermore, students often think that substances can disappear during some processes, and they are inclined to explain this fact with reference to chemical changes as a result of which masses of substances can alter. Still, this view is wrong. In addition, students believe that chemical processes lead to irreversible changes in substances, and they experience difficulties while understanding their reversible nature.
In order to help students overcome the described misconceptions, it is necessary to focus on developing an effective structure of the lesson during which it is important to focus on differences in physical and chemical processes, as well as on their indicators. During the first part of the lesson, it is necessary to focus on explaining and demonstrating physical processes and associated physical changes in certain substances. Attention should be paid to indicators of physical processes and factors that remain to be unchanged (Driver et al., 2005).
If it is possible, the second part of the lesson should include the demonstration and discussion of the chemical processes and changes associated with the same substances. It is important to demonstrate the difference in processes and changes while referring to the same substances. In other cases, it is appropriate to use substances, the changes in which are most illustrative to emphasize chemical processes.
It is a difficult task for students to understand the particulate nature of the matter. As a result, children often do not understand that the particulate nature guarantees that the matter has a fixed mass even when chemical or physical changes are observed. In this context, it is important to focus on such an aspect as the ‘conservation of matter’ (Driver et al., 2005).
Teachers should explain that the matter consists of specific particles that are known as molecules and atoms, and the quantitative aspect is very important while discussing the matter. Thus, different substances conserve their masses because of the idea associated with the ‘conservation of matter.’ From this point, when substances interact or dissolve, the matter does not disappear, and masses of substances do not change.
The problem is in the fact that, in most cases, children are inclined to ignore the idea of fixed masses and the particulate nature of the matter if they cannot observe the substance anymore. The example to support this idea is a solution of sugar. Students are inclined to concentrate on the mass of water, and they forget about particles that constitute sugar as the matter. As a result, conclusions regarding the mass of the overall solution can be wrong. Therefore, much attention should be paid to explaining the particulate nature of the matter to children.
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Driver, R., Rushworth, P., Squires, A., & Wood-Robinson, V. (2005). Making sense of secondary science: Research into children’s ideas. New York, NY: Routledge.