Brainiac Plays with Fire: Thermite versus Liquid Nitrogen

In comparison to other science shows, Brainiac is quite effective at appealing to the visceral compulsion to play with fire. In this case, they pitted scorching hot thermite against molten metal. What could be better than a battle between two of the most enjoyable science demonstration tools of all time?

Thermite is a mixture of iron oxide and aluminum. When ignited, the aluminum is oxidized and the iron oxide is reduced. If you put it in a terracotta flower pot with a sheet of metal covering the hole at the bottom, the thin strip will melt just as the reaction has completed and allow a column of molten iron to pour straight downward.

Don't forget to vote for Shelley!
Or she will pour molten iron on your liquid nitrogen.

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Just in case that wasn't enough for you, here is a video of the Brainiac cast playing with alkali metals -- which react violently with water. Am I alone in thinking that wacky science experiments are more fun when narrated with a British accent?

When alkali metals react with water, the products are a metal hydroxide, hydrogen gas, and lots of heat. As this video shows, metals at the bottom of the periodic table react far more violently than those at the top. Every high school science student should see this.

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Smashing good show, that Braniac!

They got the blogs in a bit of a tiff over the second video, though. Seems some sod decided that the bang wasn't spectacular enough, so they added explosives to make a big bang.

I try to use Braniac in my lectures, especially Dr. Bunhead, and point out when they fudge things on the side of entertainment.

By Robster, FCD (not verified) on 20 Oct 2007 #permalink

Duh Shelley is hotter than thermite.

I hate when bloggers state the obvious.

I remember back when I was in high school, I had a chemistry teacher who wouldn't have been out of place on a show like that. There was one incident, where he said that he wanted to do some demonstration (I forget which, unfortunately) involving an alkali metal for us, but unfortunately he couldn't because it had been banned from being done in schools due to being too dangerous. So instead, he dragged out a sample of the next alkali metal down the table, since apparently that experiment wasn't banned because they'd not thought that anyone would even consider doing it. I'm not sure whether he was actually being entirely honest with us (though knowing him, I'd not be surprised if he was) but either way, it makes a great story.

(And needless to say, he did the experiment in a very safety-conscious sort of way, behind a screen, with everyone at a distance and wearing safety glasses and what have you.)

Thermite is some fun stuff. The fun part about it is that it's essentially rust and aluminum shavings. That's it. I've heard stories of angry nerds using it to melt holes through the engine blocks of jocks who stole their girlfriends... or rather the girl they stare at all the time. That stuff is nasty. It oxidizes itself so there is no need for an outside fuel source.

Personally, I think they used too much thermite in that video. It completely overwhelmed the flowerpot. If it had been set up to actually drip a small amount into the nitrogen, it may have produced a different effect... but of course it wouldn't have been as cool as white hot iron shooting everywhere!

Nice videos. I'll have to look for more. I love this stuff.

wikipedia says they faked the alkali metals one by rigging the bathtub with a bomb because the real reaction was't as cool.

By Anonymous (not verified) on 21 Oct 2007 #permalink

The real reaction is cooler. It involves a fireball.

As Robster says, Brainiac does sometimes "enhance" what is shown for entertainment value, and they got called out on the alkali show for doing this without acknowledging they did so (especially the bit about caesium). According to Ben Goldacre's Bad Science (from Ka-Boom! Science! COOL!!?!):

So what happened with the caesium? ...
Deep Throat (okay, Brainiac's Dr Bunhead, aka Tom Pringle) claims: "Absolutely bloody nothing. The density of caesium ensured it hit the bottom of the bath like a lead weight. The sheer volume of water then totally drowned out the thermal shock-wave I was expecting to shatter the bath. This was an expensive filming day. They had hired part of Pinewood studios and had an ambulance and fire engine plus crew on standby. They could not go home empty handed. So they rigged a bomb in the bottom of the bath (you can see the black wire leading into the bath) and then blew the shit out of it. I must say it did look cool... [It] ate away at my conscience. But I couldn't do anything about it."

In another article, Ben describes Theodore Gray's Sodium party (emphasis added):

Theodore Gray, like a total hero, got some friends over, with refreshments, and set about launching a kilo of sodium into his private lake
...
There was an initial large explosion from the first chunk he chucked in, and then a series of secondary explosions caused by one fairly large wedge that was literally hopping across the lake. It was thrown 40 feet up into the air, then flew into the water at high speed, only to be thrown back out into the air by the resulting explosion. It only takes a few of these skips to get several hundred feet in a few seconds. The partygoers were 200 feet away ...
Now you might be asking: where's the bad science here? Well the story is, this groovy scientist with a white beard craps all over the fakesters at Brainiac ...

The videos are awesome!