Microscale Thermite Reaction

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Sparks and light are given off in a small-scale thermite reaction when two rusty iron spheres—one wrapped in aluminum foil—are struck together with a glancing blow. The collision provides enough activation energy to allow the reaction to occur, resulting in the formation of aluminum oxide and large amounts of heat. The bright yellow sparks result from microscopic amounts of extremely hot molten iron being thrown out into the air.

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I bought two large bearings at a farm rummage sale so I could do this. It took years to rust one bearing. I gave up and threw it into the wood stove. I took it out in the Spring with a good coat of rust forming. Sparks good!

AKrn

That's why in Australian coalmines they don't use alluminium underground in general.

russellpurdie

I would have never come up with this idea, although it is so obvious watching from backwards, of course. Thank you!

bataalexander

This is interesting, but is the mechanism truly the Fe2O3 + Al --> Fe + Al2O3 thermite reaction? I'm skeptical. If one takes two polished steel spheres, even smaller than those seen here in fact, and puts a plain piece of paper between them, then smacks the spheres together at even modest velocity, the paper literally pyrolyzes and explodes due simply to the conversion of kinetic energy into heat at the very small collision point. It's a type of energy focusing phenomenon similar but less dramatic to the kinds that Seth Putterman's lab explores at UCLA. So is there really a metathesis reaction going on here, or is the aluminum simply being heated, melted, and burning in air? If there are no small Fe particles left over on the ground, I suspect the latter. Have you checked with a magnet?

Muonium

How many students have smashed digits with a poorly-aimed blow?

As for determining if it is actually a thermite reaction, I'd try using a couple lumps of a different oxidized metal, perhaps copper for a nice bright green flash, but the copper may not be hard enough to cause a reaction on impact at reasonable speeds.

rcketplumber

"Where should we do the microscale thermite video?"
"Let's do it in the gray experiment chamber"
"Cool, should I wear gray?"

"No, blue."

scambroselauntrellus

Rock banging based technology is the best

sakelaine

I’m itching so bad to joke about them slapping balls together, but I’m going to resist it as best I can.

blccrfter

If you don't inspire your students to be curious, and _wanting_ to learn more, you should resign as a teacher, I think you should view their unsupervised experiment as a badge of honor, well done!

mace

I dont know if that's actually a thermite reaction. I think it's not.

Steel balls hitting each other will heat and compress the air between them, creating a shockwave. It works with clean balls and paper too.

In this case, it very well may be simply burning the molten base aluminum in the oxygen in the air, and blowing off a tiny bit of iron oxide. Considering the velocities of air, i would be very surprised if the two had a chance to react with each other. Frankly, it would look about the same since either way oxygen is bonding to molten aluminum. In fact, the air oxygen would be MORE energetic since it doesn't have to rip off of an iron.

Prove me wrong. I'd love it if this was actually a thermite reaction.

Blowing up thermite doesn't usually make the thermite react.

cHAOs