How to Do the Color Change Chameleon Chemistry Demonstration

How to Do the Color Change Chameleon Chemistry Demonstration The chemical chameleon is a wonderful color-change chemistry demonstration that may be used to illustrate redox reactions. The color change runs from purple to blue to green to orange-yellow and finally to clear. Color Change Chameleon Materials For this demonstration, you start by preparing two separate solutions: Solution A 2 mg potassium permanganate500 ml distilled water Dissolve a small amount of potassium permanganate into water. The amount isnt critical, but dont use too much or else the solution will be too deeply colored to see the color changes. Use distilled water rather than tap water to avoid problems caused by salts in tap water that affect water pH and can interfere with the reaction. The solution should be a deep purple color. Solution B 6 g sugar (sucrose)10 g sodium hydroxide (NaOH)750 ml distilled water Dissolve the sugar and sodium hydroxide in the water. The reaction between sodium hydroxide and water is exothermic, so expect some heat to be produced. This will be a clear solution. Make the Chameleon Change Colors When youre ready to start the demonstration, all you need to do is mix the two solutions together. Youll get the most dramatic effect if you swirl the mixture together to thoroughly combine the reactants. Upon mixing, the purple of the potassium permanganate solution immediately changes to blue. It changes to green fairly quickly, but it takes a few minutes for the next color change to pale orange-yellow, as manganese dioxide (MnO2) precipitates. If you let the solution sit long enough, the manganese dioxide will sink to the bottom of the flask, leaving you with a clear liquid. Chemical Chameleon Redox Reaction The color changes are the result oxidation and reduction or a redox reaction. The potassium permanganate is reduced (gains electrons), while the sugar is oxidized (loses electrons). This occurs in two steps. First, the permanangate ion (purple in solution) is reduced to form the manganate ion (green in solution): MnO4- e- → MnO42- As the reaction is proceeding, both the purple permanganate and green manganate are present, blending together to produce a solution that appears blue. Eventually, there is more green manganate, yielding a green solution. Next, the green manganate ion is further reduced and forms manganese dioxide: MnO42- 2 H2O 2 e- → MnO2 4 OH- Manganese dioxide is golden brown solid, but the particles are so small they make the solution appear to change color. Eventually, the particles will settle out of solution, leaving it clear. The chameleon demonstration is just one of many possible color change chemistry experiments you can perform. If you dont have the materials on hand for this particular demonstration, consider trying a different one. Safety Information Sucrose and distilled water are safe and non-toxic. However, appropriate safety gear (lab coat, safety goggles, gloves) should be worn when preparing the solutions and performing the demonstration. Sodium hydroxide and potassium permanganate can cause irritation and chemical burns in contact with skin or mucous membranes. The chemical solutions must be labelled and kept away from children and pets to avoid accidental ingestion. Potassium permanganate is highly toxic to aquatic organisms. In some places, pouring a small quantity of a solution down the drain is allowed. The reader is advised to consult federal, state, and local regulations for proper disposal. Fast Facts: Chemical Chameleon Science Experiment Materials Potassium permanganateSucrose (table sugar)Sodium hydroxideDistilled Water Concepts Illustrated This demonstration is a good example of an exothermic reaction. The color change is produced via a redox (oxidation-reduction) reaction. Time Required The two chemical solutions may be prepared in advance, so this demonstration is instantaneous. Level The demonstration is suitable for all age groups. High school and college chemistry students studying redox reactions will get the most out of the experiment, but it can be used to stimulate interest in chemistry and science at any age. The demonstration may be performed by any high school or college chemistry teacher. Because there are safety protocols for using potassium permanganate and sodium hydroxide, this demonstration is not suitable for unsupervised children.