Is it an acid, base, or neutral? Make your own acid-base indicator from red cabbage, then test various household substances.

A crash course on the basic differences between acids and bases, complete with a classroom-friendly experiment demonstrating the strength of such compounds using a red cabbage pH indicator.

An indicator changes color when it encounters an acid or base. There are many different types of indicators, some that are liquids and others that are concentrated on little strips of "litmus" paper.