The Chemical Chameleon

Posted by on February 23, 2011

One of the demonstrations we do in our show is the classic chemistry experiment called the Chemical Chameleon. This is a color changing reaction that proceeds on its own through a number of different beautiful colors, and involves some really interesting chemistry.

The demonstration is done by preparing two solutions.

Solution A:
About 2mg potassium permanganate (chemical symbol: KMnO4) is dissolved in 50mL of distilled water. We only need a tiny amount of this, because it creates a very intense purple color in solution and can be too dark to see if too much is used.
Solution B:
6g of sugar (C6H12O6) and 10g of sodium hydroxide (NaOH, also known as Lye) is dissolved in about 750mL of distilled water.

Note: It’s always important to use distilled water in any chemistry experiment, because we want to make sure to avoid any sources of contamination. Tap water has lots of other things in it that are good for you, but might be bad for a chemical reaction.

Simply pouring solution A into solution B gets things going! For best results, we swirl the flask to get everything well mixed. Immediately, the deep purple color of solution A changes to blue, and very quickly after that turns green. Then, much more slowly, over a few minutes, the green fades into a yellow-orange. This is actually caused by tiny solid particles of a new chemical, manganese dioxide (MnO2) that’s been formed during the reaction. If allowed to sit long enough, these will settle to the bottom and the color of the liquid will turn clear again!

Here’s a video of the experiment in action!

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(Note: This is test footage that will be replaced with a nicer demo soon.)


The Science:

Even though this experiment is easy to perform, there’s actually some really complicated and interesting chemistry going on! It involves something called a redox reaction. This basically means that new compounds are formed when one chemical takes electrons from another chemical. Here, the potassium permanganate is reduced, meaning it gains electrons, and the sugar is oxidized, meaning it loses some.

This happens in two steps. In the first step, the permanganate ion (the part of the potassium permanganate that changes) is reduced to the manganate ion:

MnO4- + e- → MnO4-2

The compound on the left is purple, and the one on the right is green. As this reaction is going, there is some purple and some green in the solution and these combine to make it look blue at the beginning.

Next,  the green manganate is reduced again into manganese dioxide:

MnO4-2 + 2H2O + 2e- → MnO2 + 4OH-

The manganese dioxide is a brown solid, but it’s in such tiny particles that it appears to make the liquid turn yellow.

So, that’s how you make colors with chemistry!

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34 Responses to The Chemical Chameleon

  1. Bill Science

    Wow Dan, That’s kinda cool! Not as cool as some of the stuff I do, but still pretty cool. :P

  2. Jane

    Where can you buy distilled water?

  3. Dan Science

    It’s available at any grocery store or Wal Mart in your area, in 1 gallon jugs. Make sure it says distilled and not “drinking” or “spring” water – not all water is the same!

  4. Gerardo

    Can you explain further the selection of the masses of the permanganate, sugar and NaOH? Does it has to have a certain concentration? I’m trying to vary the time of reaction by manipulating the concentration of either the permanganate or the NaOH,

    Cheers!

    • Dan Science

      Hey Gerardo,

      I determined the masses mostly through experimentation myself, to see what ratios produced the best demo. Concentration of any particular reactant isn’t critical, it will just affect the speed of the reaction as you suggested. The reaction only happens in an alkaline environment, so changing the NaOH concentration should definitely have an effect. On the other hand, if you use too much permanganate I’ve found the colors get too dark to see very well, so be careful to not add too much! That sounds like a very interesting experiment! Have fun with your tests, and always remember to be safe when working with chemicals (goggles and gloves especially – NaOH in the eyes is extremely nasty). Thanks for the comment, and good luck!
      ~Dan Science

  5. Lee

    I have to do a project on the element potassium and this seems like a really exciting experiment to try. It’s just that the NaOH seems to be super corrosive and maybe too dangerous to take to school. (My teacher is very sensitive about safety.) Would there be a way to achieve a similar color transformation by using a safer substance? Do you know any safer experiments involving potassium that will be okay to try in a classroom setting?
    Thank you for your help :)

    • Dan Science

      Hey Lee,
      You’re right about NaOH, and potassium permanganate is pretty nasty stuff too! It’s a strong oxidizer so it will react very strongly with a lot of things, which is bad news if you aren’t careful.
      That’s a good question about potassium, and I’ve had to spend a few days thinking about it! The trouble is that, in most experiments, the potassium doesn’t play much of a role. In the chemical chameleon, it is the permanganate ion that changes and the potassium is just there to balance the charge. Sodium permanganate would work just the same. The only thing I can think of where potassium itself has an effect is in a flame test – you dissolve a potassium salt (KCl, KOH, etc.) in methanol and ignite it, and you get a beautiful purple flame characteristic of potassium. Of course, since this involves open flames I bet your teacher wouldn’t like that very much either!
      A safer demo would be to make a solution of potassium iodide and add acid to it to precipitate elemental iodine. This is neat because it makes an actual element, but again the potassium doesn’t do much in the reaction. Good luck with your project!

  6. Rose

    I am doing this experiment in my science class and I was just wondering what exactly is the chemical equation?

    • Dan Science

      Sorry for the slow reply on this! We’ve been very busy lately with our regular jobs plus Science Brothers events! I’m glad you get to do things like this in your classroom. I’ve searched and searched for an answer to your question, and the short answer is: I’m not sure! I have not been able to find much information on the web about this reaction, and I don’t know much about organic chemistry (the part of chemistry that deals with carbon compounds, like the sugar in this one). Here is what I think might be happening:

      4 KMnO4 + 3 C6H12O6 == 4 MnO2 + 6 C3H4O3 + 4 KOH + 4 H2O

      The carbon compound on the left is glucose (sugar, C6H12O6) and the one on the right is pyruvic acid (C3H4O3). It took quite a bit of hunting and a lot of thought to puzzle that one out, but check with your teacher and see if that makes sense to them too. If you find anything else out, let me know!

  7. pradeep

    thanks for uploading such a informative page which can help us in labs .
    my question ?
    why does orange colour appear during this reaction ?

  8. Soham

    The experiment is good, but I am actually trying to perform it in front of children of 7th grade. pls make the explaination of this reaction a bit simpler to understand by the 7th graders.
    thanks,

  9. Yash Jain

    Hello Dan & Bill I just wanted to ask weather I can join your group….pls…..

  10. Priyadarsanan

    Your web page takes my memory back to the good old school days when, as a curious student, my chemistry teacher kindled my interest in it by spectacular demonstrations of chemical reactions. Years have rolled by, my hair has now shades of grey, but chemistry has still not lost its charm on me.
    As a professional metallurgist, I find this web page very informative and makes me feel like at home like the schoolboy that I was.

    • Dan Science

      That’s great! I’m glad you enjoyed the page. You should check out my YouTube channel, mrhomescientist, for more cool experiments I’ve done! It’s more advanced stuff than what we show to the kids, but I think you’ll find it interesting. What sort of metallurgy do you do?

      Sorry this reply was so slow, your comment must have gotten lost in my inbox!

  11. Christina

    Why does the color change
    in the video:?

  12. leila

    can you explain the reaction involve in each color change? thank you.

  13. Arindam Ghosh

    Hello, I’m a student of chemistry & I have a question about the above reaction. Potassium permanganate is much stronger oxidising agent in acidic medium than in alkaline medium, why the above reaction does not occur in acidic medium? Why only alkaline medium is required?

    • Dan Science

      That’s an excellent question! Information on why this reaction works is very hard to find, and there’s not much out there. My first thought is that if an acid environment is used, the reaction may speed up (since as you say, it’s a better oxidizer). So, if you use acid instead of base the color changes may happen too quickly to catch. I’ll have to test this out, see what it does, and let you know. Great comment!

  14. Bob

    Christina and Leila, the reactions are explained above you have to read using your eyes.

  15. Bob MacAdoo

    Hello Dan Science I am a high school student and I would like to know can you give me a breif explanation of the chemistry behind the reduction of permanganate and why this happens thank you!!

    • Dan Science

      I describe what happens in “The Science” section at the bottom of the post. If you have any specific questions, let us know!

  16. jahdae

    good morning, I am a student in somersfield academy Bermuda, I am performing this experiment and i would like to know what happens in the discolouration of the solution if the concentration is increased. when more sugar is added to the potassium permanganate, does the discolouration happen faster or slower?

    kind reguards,
    jahdae

    • Dan Science

      Jahdae,

      Great question, and good to see others are trying out these experiments too! In my own tests, I found that what really affected the speed of the color changes was the concentration of the base (sodium hydroxide). Having a higher concentration of hydroxide greatly speeds up the changes, and it’s actually easy to make it so fast that you miss the initial blue color. I don’t think adding more sugar would have a visible effect, but that sounds like something interesting for you to try out!

  17. Dennis B.

    2 KMnO4(aq) + 2 NaOH(aq) + 2 C6H12O6(aq) = 2 C6H11O7Na(aq) + K2MnO4(aq) + MnO2(aq) + 2 H2O(l)

    Trust me, it took me a lot of hunting to find this equation, but there it is. Also, it is classified as a redox reaction, the colour change is simply the different rates of redox between the ions. Just as a side note, you were correct, having a higher concentration of NaOH does increase the speed of which the colour changes from pink to green, because it can oxidize quicker.

    I’m doing a project on this right now, just figured I’d help out others from here on in.
    Hope this helps,
    -Dennis

  18. Dennis B.

    P.S. I did the experiment substituting NaOH with HCl, and I got a null result (the solution stayed pink). Maybe H2SO4 would work better, but as far as I know, an acidic environment as opposed to a basic one kills this experiment.
    Regards,
    -Dennis

  19. Dennis B.

    P.P.S. I used 8 mL of 0.8% w/v glucose solution, and anywhere from 2.5-10 mL of 0.33 mol/L NaOH solution with 8 mL of 0.004% w/v KMnO4, and it worked really well for anyone else trying to duplicate it.

  20. Neil C.

    Hey this is great work, but I have one question. I believe there are two redox reactions taking place in the overall reaction, obviously, causing the color changes.

    If the first redox reaction is
    reduction:MnO4- + e- –> MnO4^2-
    oxidation:C6H12O6 –> C6H12O6^+ + e-

    then what is the oxidation reaction in the second redox reaction?
    reduction: MnO4-2 + 2H2O + 2e- → MnO2 + 4OH-
    Oxidation: ???

  21. oshin

    hi…. i just watched up the video and well its awesome…. and so i decided to show this experiment in my class and my class loved it…. thanks to you guys! ;)

  22. sadia

    hello i am in class i like pistachios

  23. Nemeleu

    Is there a way to control the change in color in time?

    • Dan Science

      Yes! The pH seems to have the greatest effect on how quickly the colors change. Adding more NaOH (increasing pH) makes the reaction speed up, and using less makes the changes slower. Heating (or cooling) the solutions should speed up (or slow down) the reaction too, though I haven’t tried this myself.

  24. IES Students

    We are using this experiment for a project in school. How does the molecules change in this process?
    Nice experiment by the way.

  25. Mirelle S

    You Sirs are amazing! Great way to make young people, like me, get interested in Science. (Yeah i´m a bit of a nerd)

  26. Sheccid Mtz

    Hola, soy de mexico, mi especialidad realiza cada año una expo quimica y quiero hacer esta reaccion oscilante, podrias decirme como expondrias esto en una escuela media superior?
    Porfavor contesta lo mas antes posible, debo entregar la informacion a mi maestro el miercoles, gracias por tu atencion.

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