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Chemical Reaction Changes Color Over and Over

Posted by timothy on from the note-gratuitous-but-accurate-dig dept.

DancingFountain writes "If you have taken a college chemistry class, you may have seen this fantastic demonstration. When two clear liquids are mixed, they immediately turn yellow, and then undulate back and forth between blue-black and yellow in a mesmerizing display. Wired Science explains that the reaction, which was developed by two high school science teachers, has been rigorously studied but not fully explained."

45 of 61 comments (clear)

  1. the 'insert your politician name' effect by peter303 · · Score: 2, Insightful

    During this period when half of those running for office are being accused of changing their mind every 15 minutes, I expect many of these jokes to be posted.

    1. Re:the 'insert your politician name' effect by Bongo+Bill · · Score: 1

      So... the Clinton effect? No, wait, the Huckabee effect! No, maybe it's....

      --
      ...but is it art?
  2. Huh? by moosesocks · · Score: 3, Interesting

    I'm confused..... where's the news here?

    The reaction's notable for its cyclical nature and the fact that we don't really understand the underlying mechanisms. According to the news article, we still haven't figured it out.

    Thanks for that status update!

    --
    -- If you try to fail and succeed, which have you done? - Uli's moose
    1. Re:Huh? by bruins01 · · Score: 1

      A better question is WHEN is the news here? And the answer to that is 1973.

    2. Re:Huh? by snowraver1 · · Score: 1

      "You're not thinking fourth dimentionally" - Dr. Emmett Brown

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    3. Re:Huh? by SQLGuru · · Score: 1, Funny

      So, can you use this knowledge to make perpetual motion machine? From what I remember of my chemistry (granted, I only got a C and it was quite a few years ago), but chemical reactions give off heat.....and heat can be used to generate power.

      http://en.wikipedia.org/wiki/Perpetual_motion

      Layne

    4. Re:Huh? by The+One+and+Only · · Score: 2, Insightful

      Perpetual motion is impossible. Fundamentally. Furthermore, some chemical reactions take in heat instead of giving it off. But back to the main point, perpetual motion contradicts the second law of thermodynamics, and as a consequence, if perpetual motion machines did exist, almost everything we know about physics would be wrong.

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    5. Re:Huh? by MicktheMech · · Score: 2, Insightful

      No.

      In fact, that's the answer to all questions of the form "So, can you use X to make a perpetual motion machine?".

    6. Re:Huh? by moosesocks · · Score: 4, Informative

      Uhm. No.

      Perpetual motion machines are flat-out impossible. Conservation of energy is a *VERY* well established scientific fact.

      Chemical reactions don't necessarily release heat. Endothermic reactions tend to absorb it. The reaction mechanism here just happens to end up with a large amount of its original reactants at the end, and most likely catalyzes itself somewhere along the way.

      The reaction in question isn't exactly perpetual either. The system eventually reaches equilibrium, and the cycle stops. (Entropy -- another well-established scientific principle makes perpetual motion rather unlikely)

      If you wanted to harvest energy from the reaction, you'd have to directly absorb it from the system as the reaction is taking place. This alters the system, and will most likely result in the reaction stopping, assuming that the temperature differential is great enough to allow you to harvest any useful amount of energy (I don't recall this particular reaction getting very hot, so that seems unlikely). You'd also be limited by the second law of thermodynamics and the carnot efficency probably wouldn't be all that favorable.

      So, all in all, the reaction's rather novel, although there's nothing in our current understanding of scientific fact that dictates that it should be impossible, even though we haven't been able to piece together the exact mechanism by which the reaction actually takes place.

      --
      -- If you try to fail and succeed, which have you done? - Uli's moose
    7. Re:Huh? by Jugalator · · Score: 1

      I agree, this one could just as well have been a link to the YouTube video, because the actual story here is the spectacular effect, not what they know, or rather don't know. :-)

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      Beware: In C++, your friends can see your privates!
    8. Re:Huh? by Bandman · · Score: 1, Insightful

      The magnetic stirrer under the glass doesn't run on pixie dust...

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    9. Re:Huh? by nomel · · Score: 1

      This same type of reaction was shown on Mr. Wizard when I was a kid!
      In his, a pH indicator was added to a solution and it would go back and fourth between acidic and basic...can't remember the cause, but he explained it just fine. I think it had to do with the creation of crystals in the solution, which is why it had to be continually mixed. Could say I have a bad memory, but that was about 15 years ago.

    10. Re:Huh? by Mr2cents · · Score: 3, Informative

      The wired article itself does not provide much information, but one of its' links, more specifically this one explains a lot (including the reactions). It does say that is does not go on for ever, but repeats for "just" 15 cycles or more. It would have been cool if it went on forever, but no such luck.

      --
      "It's too bad that stupidity isn't painful." - Anton LaVey
    11. Re:Huh? by Anonymous Coward · · Score: 1, Insightful

      But back to the main point, perpetual motion contradicts the second law of thermodynamics,...

      Maybe.

      Perpetual motion machines get classified on the basis of whether they claim to violate the first law of thermodynamics (conservation of energy) or the second law of thermodynamics (limits on converting heat to other forms of energy). Whether it would be possible to have a perpetual motion machine that only violated the first law, but not the second law, is a tricky question because the first law is so fundamental to our understanding of physics (including our understanding of the second law).

      ...and as a consequence, if perpetual motion machines did exist, almost everything we know about physics would be wrong.

      Not necessarily.

      In the first place, physics has yet to develop a "Theory of Everything", (e.g. integrating the general relativity view on gravity with the quantum field theory view on forces between sub-atomic particles). Since there isn't yet a theory that "explains it all", it would be hard to come up with any experimental observation contradicted that theory.

      Second, it's important to distinguish between violations of the first law and violations of the second law.

      In the case of the first law, conservation of energy is, admittedly, pretty fundamental to the formulation of the basic laws of physics. On the other hand, suppose experimental physicists were to discover a new sub-atomic particle that continuously emitted photons. Naturally, that would require some reworking of the standard model but many of the higher level theories might well survive largely unchanged. For example, the behavior of an electron would still be accurately described by the Schrodinger equation.

      In the case of the second law, the effect on established physical theories might be even smaller. Suppose, for example, scientists discovered a particular material that developed a permanent voltage gradient across it in the presence of a strong (static) magnetic field. As long as the material got colder when the voltage gradient was used to drive a current, conservation of energy (the first law) would still be valid. The only modification that would be needed to physics would be to state that the second law applies to everything except this particular material - not really a big change.

      Anyway, getting back to the original question of whether this particular reaction constitutes perpetual motion, unfortunately the answer is "no". What's happening is that the reaction inhibits itself (a negative feedback loop). The reaction starts going but produces some stuff that causes the reaction to stop but then the stuff that stopped the reaction gets neutralized and the reaction can start going again - but then the reaction produces some stuff that causes it to stop again, etc.

    12. Re:Huh? by Zaurus · · Score: 4, Funny

      Perpetual motion machines are flat-out impossible. ...unless you're raising a toddler.
    13. Re:Huh? by fireboy1919 · · Score: 3, Insightful

      Conservation of energy is a *VERY* well established scientific fact.

      No. Conservation is a law - a postulate. Something that we're extremely certain that can't prove using other laws, but that has never, ever been wrong once. That is the fact. If we found something that violated this law, then it would no longer be considered a law. Personally, I don't consider overwhelming evidence that something has always happened a particular way within the observation of man proof that it always did or always will. Don't get me wrong: I'd never take a bet that a perpetual motion machine is going to work, but I'm not going to go around believing that reality is 100% certain to work the way that I think it does, either.

      The system eventually reaches equilibrium, and the cycle stop

      Apparently goes through about 10 cycles, according to Wikipedia.

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    14. Re:Huh? by paintballer1087 · · Score: 3, Interesting

      And that's impossible. I mean science has always gotten everything right about physics. Don't belive those crazy rumors going around that the world is spherical.... As much as we know about physics, astronomy, matter, time, space, etc... There's that much more that we don't know. I'm not saying perpetual motion is something that will ever be discovered, or if it is possible. But saying something is "impossible" because we would be wrong otherwise, puts us at the place of knowing everything. As far as we know, the second law of thermodynamics is right, but we've been proven wrong in the past, and probably will in the future.

    15. Re:Huh? by complete+loony · · Score: 1

      It doesn't go on forever.

      The reaction is always consuming IO3-, acid and hydrogen peroxide to produce ICH(COOH)2, water and oxygen. However there are a number of different reactions going on at different rates with different catalysts that change the concentrations of I-, HIO, HIO2 and I2.

      High concentrations of I2 by itself looks amber. High I2 and I- with starch turns blue / black. As the I2 is consumed the solution becomes clear.

      --
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    16. Re:Huh? by The+One+and+Only · · Score: 2, Interesting

      I was going to expand my thoughts by sharing Quine's views on knowledge, but I thought it would be total overkill. But since you brought it up--Quine teaches us that we all hold a body of beliefs that are consistent with each other, and that any given belief has more or less credence to us based upon evidence (i.e. the other beliefs within the system) and the need to make the system itself consistent. So if I am investigating a murder, and believe that one of three men committed the murder, I investigate each of them and ask for an alibi. If all three of them give me an alibi and it's corroborated, I have to decide: which one of them is lying? Or perhaps did some fourth person commit the murder? I have to toss out one belief so the others fit. (And if I really wanted to, I could hold on to any belief, just as long as I adjust the others to fit. This is what conspiracy theorists do. But that's not very practical, so Quine advises us not to do that.)

      The same process occurs in science. When we find something that seems like a perpetual motion machine, we have to either believe that it isn't a perpetual motion machine, or that the laws of thermodynamics are wrong. Given how much we have invested in the laws of thermodynamics, it's usually easier to give more credence to the notion that the alleged perpetual motion machine isn't. Now, if we had enough evidence that a supposed machine was capable of perpetual motion, then we would overturn the laws of thermodynamics. But it would take a great deal.

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    17. Re:Huh? by Lehk228 · · Score: 2, Funny

      go ahead and stop feeding him, the motions will stop in a few days.

      --
      Snowden and Manning are heroes.
    18. Re:Huh? by ceoyoyo · · Score: 3, Funny

      That's not perpetual motion. Have you noticed you're more tired since you had him? The energy has to come from somewhere you see. It just seems really impressive because you're big and he's little so when you put your energy in a little package it moves much faster.

    19. Re:Huh? by Zencyde · · Score: 1

      I don't like doing this; but, you misspelled dimensionally. You are obviously not running Firefox or Linux. I am hereby revoking your geek card. You may reapply for it in six months.

      --
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    20. Re:Huh? by jotok · · Score: 1

      Not well understood? I wouldn't say so. This and similar reactions are covered in (among other works) Goodwin's How the Leopard Changed Its Spots.

      I mean, is anything really perfectly understood? Probably not, but I think these are well-characterized.

    21. Re:Huh? by Thanshin · · Score: 1

      You may reapply for it in six months. You'll find more news about your reappliance results in slashdot, day 10/12/2024
    22. Re:Huh? by Tastecicles · · Score: 1

      Perpetual motion machines are flat-out impossible.

      You're not a parent, are you?

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  3. Just had to slip one in? by techpawn · · Score: 2, Funny

    Like Mitt Romney speaking on social issues, the undulating brew just can't make up its mind.
    did they HAVE to take a political jab in the science blog?
    --
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    1. Re:Just had to slip one in? by rk · · Score: 1

      Well, politicians are well known for sticking their noses into anything and everything, so I suppose turnabout is fair play.

    2. Re:Just had to slip one in? by framauro13 · · Score: 5, Funny

      It's ok. Republican's don't believe in science. He'll never read this.

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    3. Re:Just had to slip one in? by Digi-John · · Score: 2, Informative
      It's ok. Republican's don't believe in science. He'll never read this.

      Apparently Democrats don't believe in grammar? Oh, and if you're actually Green Party or Socialist, I apologize--I swear I'll mock you just as much as you deserve as soon as I get the chance. I'm just really busy right now; you know how it gets with work and all that... unless you're a Socialist, in which case you're probably late for your Art History 233 class.

      --
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  4. i remember this from high school by circletimessquare · · Score: 4, Informative

    it has to do with the fact that instead of the usual equilibrium present in a reaction, there are two, or three equilibriums between three or four different states, all roughly equivalent thermodynamically. they just seesaw around in circles between the equilibriums when a little energy is introduced into the mix. apparently its very tricky to get it just right. but if you do, the equilbriums bounce back and forth between each other like a pendulum or spring, and sometimes, balanced just right, like a pendulum on a grandfather clock, they can bounce back and forth for a very long time

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    1. Re:i remember this from high school by SpaceLifeForm · · Score: 1

      I recall this also. I don't recall the chemicals used,
      but the solution oscillated between purple and clear,
      eventually ending purple.

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    2. Re:i remember this from high school by Bandman · · Score: 1

      I hate to nag, but the pendulum on a grandfather clock doesn't stop due to the weights hanging on it, which turn a wheel, whi..nevermind. It's just cause of the weights at the bottom.

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    3. Re:i remember this from high school by tgd · · Score: 1

      Um, what?

      It stops because of friction in the mechanism. No friction, it would keep going forever.

  5. Looks cool by snarfies · · Score: 1

    While it looks cool, its not exactly news, is it? When I was in 4th grade I had a Hypercolor shirt that did the same thing. That was like... 1986?

  6. Iodine Clock Reaction by Anonymous Coward · · Score: 1, Interesting

    I know some people hate Wikipedia, but it has far more useful information, than this silly "article" has.

    1. Re:Iodine Clock Reaction by $RANDOMLUSER · · Score: 2, Informative

      Actually, it's this reaction TFA is talking about.

      --
      No folly is more costly than the folly of intolerant idealism. - Winston Churchill
    2. Re:Iodine Clock Reaction by $RANDOMLUSER · · Score: 1

      Mumble. Blew the link.

      --
      No folly is more costly than the folly of intolerant idealism. - Winston Churchill
  7. Instructions by tirerim · · Score: 1

    If anyone wants to know how to do this for themselves (well, assuming you can find all the components), here are some instructions.

  8. WHAT ... is your favorite colour? by Colin+Douglas+Howell · · Score: 3, Funny

    Yellow. No, blue--AAAAAAAAHHH!

    [Too bad the movie has the colors in the opposite order.]

  9. Direct Video Link by Erioll · · Score: 3, Informative

    Here's a video of it on google video: http://video.google.com/videoplay?docid=680106771263243162

  10. News from before you were born. by siglercm · · Score: 3, Funny

    I knew I had seen something like this in an article I read... THIRTY YEARS AGO...

    http://amasci.com/amateur/sciamdx.html

    Search for "Chemical reactions, oscillating".

    Sorry, kiddies. Been there, done that. Still interesting, though.

    --
    sigfault (core dumped)
  11. Re:Huh? Umm, maybe it's a... by davidsyes · · Score: 1

    Reactionary "collide-o-scope"?

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  12. Dig out your chemistry set... by HotNeedleOfInquiry · · Score: 2, Informative

    Here's the procedure for demonstrating the reaction

    http://www.chem.leeds.ac.uk/delights/texts/expt_11.html

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  13. Hey! I Know Them... by Talkischeap · · Score: 1

    Cool!

    Warren & Tom make Slash Dot.

    I know them from the international Caving community, where they are well regarded.

    Somewhere I have a great humorous photo I shot of Warren in an "administratively closed" cave in the Mojave desert, and then we promptly got arrested for trespassing.

    But I talked us out of it.

    Gotta watch out for those science teachers.

    --
    If it don't GO... chrome it. ~ Frank Banks
  14. oscillating reactions are reasonably well known by StandardDeviant · · Score: 3, Interesting

    I did a math paper for a mathematical modeling class during my chemistry undergrad on the BZ reaction mechanism, which is another oscillator like the system in TFA. It's not a perpetual oscillation, but with precisely controlled reagents you can get some pretty long-lasting oscillations (precisely as in on the order of hundredths of a mole, iirc). There's a really good little book in the oxford chemistry primers series (series as a whole is quite nice for accessible, focused introductions to various fields) on this topic: Oscillations, Waves, and Chaos in Chemical Kinetics by Scott.

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