Abstract: Starch, a plant polysaccharide typically comprising amylose and amylopectin, exhibits a well-known property of turning blue upon encountering iodine. This color reaction, celebrated for its sensitivity, has found widespread application in experiments aimed at detecting iodine or starch. However, the coloration of starch upon iodine exposure is not always blue; rather, it varies depending on the starch composition. This study explores the diverse coloration exhibited by different food starches under various conditions (starch concentration, iodophor concentration, temperature, pH, polymerization degree), capturing the enchanting encounter between starch and iodine. Utilizing common food starches and iodophors as experimental materials, this educational experiment is cost-effective, environmentally friendly, non-toxic, and user-friendly. By harnessing the distinct color reactions of starch and iodine, we create environmentally friendly multi-color ink, seamlessly integrating traditional calligraphy and Chinese painting techniques. Additionally, we explore captivating chemical experiments such as the magical iodine clock reaction, iodine fumigation for fingerprint analysis, and the preparation of non-Newtonian fluids from starch. With its strong appeal and broad audience reach, this experiment effectively employs gradient science popularization strategies. Through hands-on offline activities, participants experience the beauty of chemistry firsthand, fostering a deep appreciation and passion for the subject. The experiment yields significant outcomes in promoting scientific literacy and cultivating interest in chemistry among learners.

Key words: Starch, Iodine, Coloration, Gradient science popularization