This experiment is for advanced students.

Potassium permanganate (KMnO₄) in water turns an intense, deep, purple. It is important in the film industry for aging props and clothing to make them look much older than they are.

Also, artists use it in bone carving. People who carve antlers and bone use KMnO₄ to darken the surface of the bone to make it look aged. They make the carving, soak it in potassium permanganate, then carve more, and repeat. The end result is a carving that has a light golden brown color. More dipping will darken the carving even more.

Potassium permanganate is going to undergo a chemical change with this activity. In this experiment, we will be able to witness several indicators of chemical change. Color changes, bubbles from gas generation, temperature change, and color disappearance are all indicators of chemical changes.

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Examples of chemical color changes we might be familiar with are autumn leaves changing color and a half eaten apple quickly turning brown.

Physical changes can mimic the indicators of chemical change, so we will need to always think through what we observe and then decide whether it is a physical or chemical change. Physical changes that mimic chemical changes can be color and temperature. The key is that physical changes are changes in state (solid, liquid, gas, sublimation) or changes in the condition of the material. In our pursuit of science knowledge, we will observe many physical and chemical changes. We need to be able to identify them accurately to really understand what is happening in an experiment.

Materials:

• 3% Hydrogen peroxide (KMnO4) (MSDS)
• Test tube rack
• 2 test tubes
• Potassium permanganate (KMnO4) (MSDS)
• Sodium hydrogen sulfate (NaHSO4) (MSDS) Sodium hydrogen sulfate is very toxic. Respect it, handle it carefully and responsibly. Do not take it for granted.
• Measuring syringe
• Water
• Measuring spoon
• Solid rubber stopper

NOTE: Be very careful when handling the sodium hydrogen sulfate – it’s highly corrosive and dangerous when wet.  Handle this chemical only with gloves, and be sure to read over the MSDS before using.

Always cap your chemicals after use and set them aside where they won’t get in the way. Your lab area should always be clear, clean, and uncluttered. Water and a fire extinguisher should be within arm’s reach. Always clean equipment before using any of it on another chemical.

Potassium permanganate is going to undergo a chemical reaction that will turn the deep violet or purple solution clear. It is a very cool experiment and looks like a lot of fun.

C3000: Experiment 102

Download Student Worksheet & Exercises

Here’s what’s going on in this experiment:

KMnO₄ + NaHSO₄ + H₂O₂ = MnSO₄ + O₂ + NaOH + KOH

Potassium permanganate is added to sodium hydroxide, and then hydrogen peroxide is added and quickly capped.

MnSO₄ + O₂ + NaOH + KOH

The product of the reaction is manganese sulfate, oxygen, sodium hydroxide, and potassium hydroxide. The remaining chemicals are all clear, so the desired result is obtained.

Cleanup: Clean everything thoroughly after you are finished with the lab. After cleaning with soap and water, rinse thoroughly. Chemists use the rule of “three” in cleaning glassware and tools. After washing, chemists rinse out all visible soap and then rinse three times more.

Storage: Place cleaned tools and glassware in their respective storage places.

Disposal: Liquids can be washed down the drain

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