- 論集 (ISSN:03891658)
- vol.59, no.2, pp.93-102, 2012-12
When the binary solution, whichi is composed of a solute and a solvent, is diluted with its solvent, volume is not conserved; the total volume of an original solution and an added solvent is not equal to that of its diluted solution. This phenomenon is well known, however, it has been never quantitatively discussed from the viewpoint of science education. In this paper, the method of estimating the volume of a diluted binary solution is first derived. The volume of a diluted solution is obtained from volumes and densities of an original solution and an added solvent and from the density of the diluted solution. Densities of the original and diluted solutions are calculated using an empirical equation, which is a power function of the mass fraction of a solute. Successively, our method is applied to D-glucose and sucrose aqueous solutions in order to examine volume changes in diluting these solutions with water at 20℃, The concentration ranges of original D-glucose and sucrose aqueous solutions are 0-0.6000 and 0-0.8000 mass fractions of solutes respectively. The volume ratios of the original solution to the added solvent are 1.000 mL: 5.000mL, 2.000mL:4.000mL, 3.000mL:3.000mL, 4.000mL:2.000mL, and 5.000mL:1.000mL, For both aqueous solutions, volumes decrease over the 0.2500 solute mass fraction range, and they reach minimum values (5.983mL for D-glucose and 5.963mL for sucrose aqueous solution) at the ratio 3.000mL: 3.000mL. Although these volume changes are too small to be detected using our microscale experiments, the obvious volume decreases are recognized after diluting original solutions Estimating volumes of diluted aqueous solutions is very simple and easy, and it is concluded that our method is useful as teaching material for high school science.