Development of Teaching Materials for Understanding the Concept of Reaction Rate Using Prussian Blue Watercolor Paint

Abstract

Based on an alkaline hydrolysis reaction of Prussian blue, we developed experiments for learning the difference in reaction rate depending on the reagent added to the Prussian blue suspension and the difference depending on the temperature of the suspension. A color change was observed when sodium hydroxide or potassium hydroxide was added to the suspension, which is used as commercial watercolor paint. In either case, the color changes from dark blue to light yellow, but the time required for the color to change varies significantly, and the students can visually confirm the difference in the reaction rate depending on the reagent added. As a preliminary experiment, a spectrophotometer was utilized to analyze the reaction rate of samples. The reaction rate of each alkaline hydrolysis reaction can be analyzed using a primary reaction formula. We were able to estimate the activation energy in each case using an Arrhenius plot. Based on these experimental results, teaching materials using the color change of the suspension were developed. From the results of the questionnaire on the class practice, it was clear that (1) the difference in reaction rate due to temperature change and (2) the difference in decomposition reaction rate between two alkaline solutions and can be learned.