Chemical Reaction Changes Color Over and Over

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."

the 'insert your politician name' effect

[peter303]

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.

Re:

[Bongo Bill]

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

Huh?

[moosesocks]

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!

Re:

[bruins01]

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

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[snowraver1]

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

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[Zencyde]

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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[Thanshin]

You may reapply for it in six months.

You'll find more news about your reappliance results in slashdot, day 10/12/2024

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[SQLGuru]

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 [wikipedia.org]

Layne

Re:

[The One and Only]

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.

Re:

[Anonymous Coward]

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 fundame

Re:

[paintballer1087]

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 k

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[The One and Only]

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 ea

Re:

[MicktheMech]

No.

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

Re:Huh?

[moosesocks]

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.

Re:Huh?

[Zaurus]

Perpetual motion machines are flat-out impossible.

...unless you're raising a toddler.

Re:

[Lehk228]

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

Re:Huh?

[ceoyoyo]

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.

Re:Huh?

[fireboy1919]

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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[jotok]

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.

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[Tastecicles]

Perpetual motion machines are flat-out impossible.

You're not a parent, are you?

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[Bandman]

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

Re:Huh?

[Mr2cents]

The wired article itself does not provide much information, but one of its' links, more specifically this one [leeds.ac.uk] 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.

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[complete loony]

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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[Jugalator]

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. :-)

Re:Huh? Umm, maybe it's a...

[davidsyes]

Reactionary "collide-o-scope"?

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[nomel]

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.

Just had to slip one in?

[techpawn]

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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[rk]

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

Re:Just had to slip one in?

[framauro13]

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

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[Digi-John]

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.

i remember this from high school

[circletimessquare]

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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[SpaceLifeForm]

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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[Bandman]

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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[tgd]

Um, what?

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

Looks cool

[snarfies]

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?

Iodine Clock Reaction

[Anonymous Coward]

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

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[$RANDOMLUSER]

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

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[$RANDOMLUSER]

Mumble. Blew the link. [wikipedia.org]

Instructions

[tirerim]

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

Direct Video Link

[Erioll]

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

WHAT ... is your favorite colour?

[Colin Douglas Howell]

Yellow. No, blue--AAAAAAAAHHH!

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

News from before you were born.

[siglercm]

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

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

Search for "Chemical reactions, oscillating".

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

Dig out your chemistry set...

[HotNeedleOfInquiry]

Here's the procedure for demonstrating the reaction

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

Hey! I Know Them...

[Talkischeap]

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.

oscillating reactions are reasonably well known

[StandardDeviant]

I did a math paper for a mathematical modeling class during my chemistry undergrad on the BZ reaction mechanism [wikipedia.org], 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 [oup.com] by Scott.