How can you turn a yellow solution into a whole rainbow?
Warning! Only under adult supervision.
- 5 disposable cups;
- thymol blue solution;
- sodium hydrogen sulfate solution;
- citric acid solution;
- sodium carbonate solution;
- sodium bicarbonate.
Pour into 5 separate glasses: a solution of sodium hydrogen sulfate, a solution of citric acid, a 1:1 mixture of citric acid and sodium carbonate solutions, a solution of sodium carbonate, and sodium bicarbonate. Then, distribute some thymol blue equally into each glass. This creates a rainbow!
Acid-base indicators are substances that change colors depending on the pH of the solution they’re in. Thymol blue is one such indicator. As it indicates, the sodium hydrosulfate solution is strongly acidic (pH <1), the citric acid solution is acidic (pH ≈ 2 in the vial), the mixture of citric acid and sodium carbonate solutions is in the middle (3 < pH <8), the sodium carbonate solution is slightly alkaline (pH ≈ 9), and sodium bicarbonate is strongly alkaline (pH > 10). You can also use thymol blue to test liquids you have around your house, such as lemon juice, soap, milk, and many other products and household chemicals.
This and other amazing experiments are waiting for you in the MEL Chemistry subscription!