Writing with Electricity - Chemical Demonstration Kit

Get a charge out of writing with electricity! Demonstrate the key concepts of electrochemistry, including anodic and cathodic reactions, by using a copper “pen” to follow the flow of electrons in the electrolysis of aqueous potassium iodide. Students will observe secret messages that appear in filter paper containing starch and phenolphthalein indicators. The blue-black starch iodine complex is visible when the copper pen is negative, and the red color of phenolphthalein in base appears when the pen is positive. Identify the reactions responsible for each color change—and watch the electrons and concepts flow!

Concepts: Electrochemistry, acid–base indicators.
Time Required: 15 minutes
Materials Provided: Potassium iodide, starch, phenolphthalein indicator solution, aluminum pan, filter paper, 9-V battery, battery clips, copper wire, and disposable pipets.