Chemical Chameleon
Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★☆ Some safety precautions required to perform safely
Categories: Colour Changes, Oxidation and Reduction
Alternative titles: Rainbow Redox Reaction
Summary
The chemical chameleon demonstration produces a sequence of color changes - purple to blue, green, orange-yellow, and finally clear, when potassium permanganate reacts with sugar in alkaline solution. The striking changes illustrate redox reactions and the reduction of manganese through several oxidation states.
Procedure
Prepare Solution A: dissolve a small amount of potassium permanganate (about 2 mg) in 500 mL of distilled water to make a deep purple solution.
Prepare Solution B: dissolve 6 g of sugar (sucrose) and 10 g of sodium hydroxide (NaOH) in 750 mL of distilled water to make a clear solution.
Pour Solution A into Solution B and swirl gently.
Observe the color sequence: purple → blue → green → orange-yellow → clear, as manganese compounds form and precipitate.
Links
Variations
Try adjusting the concentration of permanganate to slow down or speed up the reaction.
Replace sucrose with other reducing sugars (e.g., glucose, fructose) and compare the timing of color changes.
Perform the demonstration in a transparent column for a more dramatic visual effect.
Safety Precautions
Wear goggles, gloves, and a lab coat.
Sodium hydroxide is caustic and can burn skin and eyes.
Potassium permanganate is a strong oxidizer and stains skin and surfaces; it is toxic to aquatic life.
Dispose of solutions according to local hazardous waste regulations.
Clearly label all solutions and keep them away from children and pets.
Questions to Consider
What is being oxidized and what is being reduced in this reaction? (Sugar is oxidized, permanganate is reduced.)
Why does the solution appear blue at first instead of green? (Both purple MnO₄⁻ and green MnO₄²⁻ are present, producing a blue mixture.)
What solid forms later in the reaction? (Brown MnO₂ precipitate.)
How does this experiment illustrate multiple oxidation states of a transition metal? (Manganese passes through +7, +6, and +4 states during the reaction.)