DESCRIPTION:
This demo has a solution in a flask that changes color from pink to blue to green to yellow to orange as the solution is stirred. The different colors are due to the different oxidation states of manganese.
TOPICS COVERED:
– redox
– color change
– chemical change
MATERIALS NEEDED:
– 250mL flask
– 0.15M sugar solution
– 0.33M NaOH
– a few mL of a dilute KMnO4 solution
PROCEDURE:
1. Add equal volumes of sugar and NaOH solutions to the flask
2. Add 5-10 drops of a KMnO4 solution, too much KMnO4 will make the color changes too dark to see
ADDITIONAL COMMENTS:
Adding more KMnO4 when the reaction is almost over, will recharge it to go through the colors again, but this will only work a few times until the sugar and NaOH are used up.
SAFETY:
KMnO4 is a strong oxidizer and even in dilute concentrations can irritate skin and cause stains, goggles should be worn at all times and caution taken.