微小概念の発達と指導の可能性について

Recently, even the elementary schools have a tendency to teach the students in the classroom some aspects on atoms and molecules. It is rather interesting to find out what grade is most appropriate to start having the students gain knowledge on atomic and molecular physics.
As a subject of my study, I started out with the elementary and junior high school students making a survey as to the extent of knowledge they had on the concept of the small matter and to find out as to when was the best time to start teaching these students this subject. After following my study, I came to the following conclusion :
1. Concept towards visible small matter at elementary school level was at the most, that of salt and sugar.
2. Concept towards invisible small matter at elementary school level was at the most, microscopic small matter. At the sixth grade level, approximately 5% were able to understand molecular small matter while at the junior high school level, 50% understood molecular small matter. The other 50% together with the majority of the elementary school students were not able to grasp the concept of molecular small matter, that is, they understood only microscopic small matter.
3. Comparison of the visible size for infer the molecules metaphorically was comprehended by 30-40% of elementary school children and 60% of junior high school students.
But in the case of the comparison of the invisible size of molecules metaphorically with that of visible molecules metaphorically, the percentage of comprehension was much smaller.
4. The extent of understanding small matter did not have any relation to the student's intelligence or scholarity ability, nor did it have any relation to regional differences.