Using Visual Learning to Teach Electrolysis at the Introductory Level

Electrolysis is an essential but often difficult topic for first-year engineering students, because the processes are more complex than those of other introductory chemistry subjects. This paper introduces a simple classroom demonstration that enables students to visualize acid–base changes during electrolysis. The setup uses platinum electrodes, filter paper soaked with aqueous KNO3, and red cabbage juice as a pH indicator. Within about 10 min, the solution near the anode turns red, while the cathode region shifts from green to yellow, providing a direct visual link between observed color changes and the underlying half-reactions. Designed for introductory general chemistry courses, this demonstration is especially useful when safety concerns or limited class time make multiple laboratory experiments impractical. Pre- and post-test results showed marked improvement in students’ ability to predict electrode processes occurring during electrolysis.