Practical Research to Promote Successful Understanding of the Concept “Particle Size in Solution” in Lower Secondary Science

Abstract

The majority of first-year lower secondary school students learn in textbooks that substances in solution “become small invisible particles,” but many different interpretations are possible. In addition, there have been many attempts to convey the concept of particles to students in that cohort, but they have requires prior comprehensive knowledge as well as special lab equipment. In this study, the proposed learning method enables students to concretely imagine the size of particles in a solution and to conduct experiments based on what they have already learned. This study verified whether a dialysis experiment using a colloidal solution and a cellophane membrane is effective as a method for allowing students in the first grade of lower secondary school to correctly visualize the size of particles. Cellophane is a substance that is used even in second- and third-grade science, so becoming familiar with it in the first grade is desirable for future learning. In addition, since the iron (III) chloride aqueous solution used is colored, it is easy for even those who does not have prior knowledge to understand the phenomenon occurring in the experiment. Furthermore, this material can be easily prepared for the colloidal solution. Incidentally, the pupils in this study had already learned about hydrochloric acid, which is produced at the same time. From the results of this study, it was found that even if the materials are used for the first time, the students can fully infer the concept of particles based on the changes during the experiment and their prior knowledge. Moreover, it was confirmed that they were able to concretely imagine the size of “small invisible particles” in the solution and to correctly establish the image. The devised learning method utilizing a colloidal solution and a cellophane membrane was therefore confirmed to be effective in promoting a correct and concrete understanding of the size of particles in solution among the students.