Durham Academy
Danielle McNeil, Class of 2009, makes a pH Rainbow Tube by filling it with a solution that reacts differently to acids and bases. By putting an acid in one end and a base in the other she's created a rainbow!
Universal indicator is a mixture of dyes that displays a variety of colors depending on the pH. Red, orange, and yellow appear at lower pH (<7) while blue, violet, and purple appear at a higher pH (>7). Equal amounts of hydrochloric acid and sodium hydroxide are used in this demonstration.