Abstract

It is apparent that no changes occur in its total mass, total weight, and in total volume, even when the shape of a clod of clay of a definite mass is modified by any methods. Some children think, however, that some of the total mass, the total weight and the total volume of this clay change during the procedure of modification in its shape. The authors investigated, therefore, at about what age the children get the right ideas concerning the conservations of mass, weight and of volume of a matter, which are independent of the change in its shape. The number of the school children on whom the investigations were made was 74 (the 1st grade…24, the 2nd grade…25, the 3rd grade…25). On the other hand, it was necessary for the authors to investigate whether the concept of volume has already been fixed in the minds of children before starting their investigations concerning the degree of fixation of the conservation of volume in the children. In order to make these investigations, some special tools (such as clay balls, rods of brass and styrene balls) were used, and the children were questioned whether the surface-level of the matter in a beaker (water, powder or soil) moves upward or downward when one of the above described tools was completely immersed in it. During the processes of the investigations, the followings became obvious. (1) In the course of growth of children, the concept of conservation of mass, that of conservation of weight, that of volume and that of conservation of volume are settled in the minds of children in their order. (2) The concept of conservation of mass is of very vague character in the minds of the very young children. But, as the concept of conservation of weight or the concept of conservation of volume is fixed, the original concept of conservation of mass is strengthened with them and comes to possess the very firm scientific character. This second conclusion teaches us that in the course of education, it is important for the teachers to suggest their children how the law (or knowledge) which has just been discovered in the present classroom can be used for re-constracting some old laws (or knowledges) which were already caught in the past or for detecting any new laws (or knowledges) in the future. The number of the children in each of the definite degrees of growth of minds (putting the number of the whole children investigated as 100) is shown in Tables 11~13 which indicate that the four concepts investigated become settled earlier in boys' minds than in girls' minds.