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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."
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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Actually, it's this reaction TFA is talking about.
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Here's a video of it on google video: http://video.google.com/videoplay?docid=680106771263243162
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.
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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.
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Here's the procedure for demonstrating the reaction
http://www.chem.leeds.ac.uk/delights/texts/expt_11.html
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