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
Chemical Chameleon Experiment - Rychlá Chemie:
Chemical Chameleon Demonstration (with NaOH, KMnO4, and Sucrose) - 2 AM Productions:
📄 How to Do the Color Change Chameleon Chemistry Demonstration - ThoughtCo: https://www.thoughtco.com/how-to-do-color-change-chameleon-4057571
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.)