Abstract
The purpose of this study is to develop learning materials for pupils to foster scientific thinking skills in school science. In this paper, the authors described two cases of primary school science lessons involving the processes of constructing mental models of their own ideas and discussing intensively which one is the most plausible model in a group or whole class at fifth and sixth grade levels in different schools. Invisible gases like carbon dioxide and air were introduced as the subject in these lessons. Almost all pupils could construct visible mental models in both cases. Most of the 5th graders and half of the 6th graders had misconceptions about gases at the beginning of the lesson. Judging from their essays on their impressions and reflections on the lessons, they enjoyed doing the experiments on handling of gases, constructing visible models from invisible phenomena, and understanding the concept of gas. After both lessons, students were given a questionnaire to survey their recognition of ways of looking at things scientifically. As a result, it may be said that learning materials using invisible gases are very effective to achieve these objectives.
