invisible ink

Oxidation is any chemical reaction that involves the moving and losing of electrons. When that happens, an object’s properties change. For example, when iron reacts with oxygen it forms a chemical called rust. You can also watch oxidation when you cut an apple. An apple slice will turn brown when left on the counter.

Fun tip! You can slow the oxidation process by putting lemon juice on the apple! The oxygen reacts with the ascorbic acid (Vitamin C) in the lemon juice before it reacts with the polyphenol oxidase enzyme in the apple.

For the invisible ink, when you heat up the organic compound, the lemon juice oxidizes more rapidly and turns brown, which helps us see the secret message.