Spatial Visualization of Chemical Reactions in a Hydrogel

Educational experiments that spatially visualize chemical reactions in hydrogels have been developed and demonstrated, taking advantage of the slow diffusion in hydrogels. A solution containing a reactant was diffused into a hydrogel containing a counter-reactant, resulting in a color change. The distance of the color change depended on the concentration of the reagent, which is beneficial for quantitatively observing the degree of the chemical reaction. First-year university students performed the experiment with interest and demonstrated good learning outcomes. The demonstrations shown in this study, along with the failure cases, will serve as guidelines for visualizing other chemical reactions in hydrogels.