To clarify the previous writeup: You actually a mix of finely ground aluminium (not the oxide), and Iron (III) oxide (i.e. Fe₂O₃). In fact it only works with the gamma allotrope of the iron (III) oxide.

You need to kickstart the reaction with some serious stuff, for example, lighting magnesium ribbon. Once you kick the reactants over the activation energy, a substitution reaction occurs, with the aluminium taking the oxygen away from the iron, leaving you with molten iron coming out at 3000 kelvin or so, in other words, bloody hot! It's usually enough to melt the reaction container. Hence its name (thermos being the Greek for heat).

Although there are anarchic uses of thermite, there are also practical ones; and this is where it came about. When they lay railroad tracks, the rails come in lengths of a few meters; but this isn't really very useful, so you have to somehow "weld" the rails together. But surface welding is obviously out of the question if you're going to have hundred-ton juggernauts running over the top of it. What to do? Get a mold in the shape of a rail with a small hole on top, insert two rails in either side, put a container of thermite on top, get the reaction started, let the molten iron fall into the gap, wait for it to cool down, remove the mold, bit of sanding and polishing and voila, you have a perfect, solid, all-through weld.

Speaking of thermite and railroads, there's another kind of thermite which involves, I think, aluminum powder and copper oxide. Same idea, except that when you're done, you're left with molten copper. The railroad connection is that it's how you attach signal wires and bonding jumpers to the rails, and also the big ground return cables on electric trolley lines.

Technically speaking, of course, aluminum powder is cool shit. Due to the fact that aluminum (or rather, aluminium if you're from the other side of the pond) oxides tend to have ridiculously negative heat of formation, interesting things can happen. Interesting to male teenagers like myself, of course, because negative heat of formation means energy is liberated when it is created. There are actually many metal oxides that will work in thermite, and the reaction is usually called a redox (reduction/oxidation) reaction, not a substitution one. Thermite is good for burning holes in things and impromptu welding

In any case, I didn't learn how to build this "bomb" on the internet ... I learned how in AP Chemistry, thank you very much.

Thermite is a very explosive mixture of aluminum powder and Iron (III) oxide. It was first invented by Dr. Hans Goldschmidt in 1893. He first used it as a welding tool for railroad tracks: once the thermite ignited and became molten, it would melt through the container into a that connects two railroad tracks. Then it would cool, forming one long track.

Okay, so enough of the boring facts. Let's have some FUN with this!

Chances are, if you're a male teenager, you like explosions. Hell, you might even like them if you're female. ... You know what? Everyone loves explosions. So this writeup is for you! It'll show you how to make an extremely dangerous explosion with but a few items, ultimately making Thermite.

WARNING! THIS EXPERIMENT IS VERY DANGEROUS. I'M NOT FUCKING KIDDING. ONCE THE THERMITE IS IGNITED, YOU CAN'T SMOLDER IT WITH ANYTHING! Water will turn into steam upon hitting the thermite once ignited, and dry ice will simply melt. It's highly reactive and reaches about 2500 °C. You MUST do this outside, and in an area where there isn't a lot of flammable stuff. Indeed, be very careful! You could very easily burn your house, yard, or yourself if you're a moron here! Want a video of this? http://video.google.com/videoplay?docid=-7231843493488769585

Materials
-Iron (III) Oxide (aka rust. Scrape some rust off of some stuff that has it)
-Aluminum powder (notes on acquiring this later)
-Flower pot (for holding the mixture)
-OPTIONAL: Scale (for measuring mass and getting the best reaction)
-Magnesium ribbon (alternatively, a 4th of July sparkler or firework thing will do. Basically, anything that can act as a fuse and gets hot enough)

Getting aluminum powder - Aluminum powder can be bought at paint stores, for it is used to make paints shiny and metallic. However, don't buy large quantities of it, lest you want the FBI on your ass. Alternatively, Etch-A-Sketches have Aluminum powder. If you're that desperate, you could probably take some aluminum foil or a soda can and scrape some off with some sort of ROUGH file (Though be sure to clean the file thoroughly afterwards, or else you run the risk of a spontaneous thermite reaction taking place).

Getting iron(III) oxide - This is easy. Scrape some rust off of places. If you can't for some reasons, you could run a large magnet over beach sand; iron (III) oxide is abundant on beaches. Also, according to WikiBooks:

Alternatively, burning steel wool will form Iron Oxide but is highly ineffective for making thermite using this formula. A more effective way is to mix bleach with fine steel wool. The reaction is quick. Adding vineger after mixing the steel wool and bleach together in a 2:1 ratio greatly increases the reaction speed and rust is produced instantly however the vineger and bleach (even in the presence of iron) produces toxic chlorine gas. This should only be done outside or in a fume hood

Step 1: Mix the rust and the aluminum powder into the flower pot. It is recommended that if you're trying this on your own, you use a VERY SMALL quantity of the mixture. One small bag full of thermite is enough to melt right through the engine block of a car, if you want an example. For maximum effiency, use your scale to get a ratio of 1 Aluminum:3 rust (by mass). This is simply the result of the stoichiometry of the chemical reaction. Mix the mixture well.(NOTE: STORING THERMITE IS DANGEROUS! If it ever ignites for some reason, the results could be dangerous. If you make the mixture, you should use it, not store it)

Step 2: Find a good open space to work in. Seriously. You don't want anything nearby you catching fire. Like, for example, grass. This would be a Bad Thing. One possibility is digging a small crater for this.

Step 3: With the mixture in the flower pot, set your fuse inside it. One possibility is the magnesium strip: Light one end of it with a butane lighter, with the other end inside the thermite itself. Some sparklers will also work, as I mentioned above. One more possibility is using the end of a match. To do this, stick the head of a match inside the thermite, then using another match or a lighter, light the wooden end of the match. The flame should crawl down to the match's head and ignite the thermite. Whatever method you use, STAND THE FUCK BACK!

Step 4: Watch it. Be careful. The reaction is HIGHLY exothermic, and can reach 2500 °C. It releases 851 kiloJoules per mole. A whole lotta fucking heat. You should see this very easily when it reacts: the mixture of powder should become molten and start sparking and whatnot. Obviously, you shouldn't touch this. It's very hot. And don't try to smolder it with, say, water or anything: it won't work. When the reaction is done, you should be left with a glowing molten core. Wait until this cools down on its own, sorry, you can't do anything about it. When this happens, that's the end of the reaction. I hope you didn't kill yourself or burn your house down.

What's happening here? Well, essentially, aluminum is a more reactive metal than iron. It literally strips the oxygen atoms from the iron(III) oxide in a highly exothermic single replacement reaction. You could easily use, say, Copper (II) oxide, but this isn't as effective a reaction. But it still works.

Fe₂O₃ + 2 Al --> Al₂O₃ + 2 Fe + 851.5 kJ

For the more visually inclined, here's a badass video of the thermite reaction causing some destruction, taken from the TV show Brainiac. http://youtube.com/watch?v=WrCWLpRc1yM

Disclaimer

Please don't sue me. Also, to the people tapping this, I swear I'm not a terrorist. Please don't arrest me, I have my whole life ahead of me.

fledy is broadly right, just a few minor points I want to make

 

Thermite is a very explosive mixture of aluminum powder and Iron (III) oxide.

Thermite is not explosive. An explosive is a compound where a shockwave goes through the material faster than the speed of sound. What thermite does is burn very hot. It is nothing more than a campfire but with the oxidiser contained in the mixture and burning a lot hotter. Also, it liberates molten iron as opposed to smoke but same principle.

WARNING! THIS EXPERIMENT IS VERY DANGEROUS. I'M NOT FUCKING KIDDING. ONCE THE THERMITE IS IGNITED, YOU CAN'T SMOLDER IT WITH ANYTHING!

This is unfortunately correct. Because thermite contains its own fuel, oxidiser and heat source (once its lit) it is near impossible to extinguish.

-Magnesium ribbon (alternatively, a 4th of July sparkler or firework thing will do. Basically, anything that can act as a fuse and gets hot enough)

Potassium permanganate and glycerin will also do the trick, won't blow out in wind and has a nice delay.

 

you could probably take some aluminum foil or a soda can and scrape some off with some sort of ROUGH file (Though be sure to clean the file thoroughly afterwards, or else you run the risk of a spontaneous thermite reaction taking place).

Given the ridiculous activation energy, you'd be hard pressed to ignite a thermite reaction on a mild steel file with binder coated aluminium (the aluminium will have probably been oxidised and coated to allow the ink for the cans design to stick)

 

A more effective way is to mix bleach with fine steel wool. The reaction is quick. Adding vineger after mixing the steel wool and bleach together in a 2:1 ratio greatly increases the reaction speed and rust is produced instantly however the vineger and bleach (even in the presence of iron) produces toxic chlorine gas. This should only be done outside or in a fume hood

No comment, I've had a few expeiences with toxic gases during my idiotic home experiments. please do it outside with a strong breeze, chlorine is not nice stuff. For a sample idea, find a bottle of strong ammonia (non scented). Open the top and cautiously waft some towards your nose. When you decide that you're tough enough to handle it, feel free to have a deep sniff from the bottle. When, 10 seconds later you can breathe again you will know what chlorine poisoning feels like.

(NOTE: STORING THERMITE IS DANGEROUS! If it ever ignites for some reason, the results could be dangerous. If you make the mixture, you should use it, not store it)

This is frankly rubbish. Thermite is about as safe as you can get. Seriously you should (theoretically) be able to jump in a fire with your pockets full of the stuff and the only damage you'll get is from the flames. Because of thermite's high activation energy, as long as its stored somewhere vaguely airtight it should be fine for months. Bear in mind what you need to set it off. Matches won't work, lighters won't work, blowtorches take a long time to work. It's almost certainly more dangerous keeping firelighters in your house compared to thermite in your garage. (This is no excuse for making or keeping thermite. It is nasty shit and will burn holes in damn near anything. Safe as it is, please be careful with it)

A Note From "Safety Bear^TM"

It is against E2 convention to address other writeups in a node, as they may disappear. This writeup will disappear as soon as its contents are absorbed into other writeups within this nodeshell.

With all due respect to the caution about moving far away from a thermite ignition reaction, it is imperative that whilst watching your handiwork explode in a devastatingly beautiful symphony of yellows, white, and oranges - DO SO WHILE WEARING SAFETY GLASSES. Sure, you may be 50 yards away from your reaction but what's a little discomfort/nerdiness compared to the loss of one's eyesight.

The powders used in thermite may contain tiny bits that'll wreak havoc with your lungs. Wear little white disposable masks. Like Michael Jackson. No, I'm serious about this.

Although you may have dug a proper crater for your reaction, has it occurred to you to check for "call before you dig" signs in the area, notifying of underground wires/gas lines?

It goes without saying that prudence must be used when selecting a locale. Has it occurred to you that the spot you've chosen for your Satanic Fire From Hell^TM may contain flammable/poisonous substances in the ground (i.e., an old industrial lot). Or worse, a tank with the residue of kerosene/gasoline underground?

The writeup directly hereinabove recommends huffing* ammonia vapors to "see what it's like to stop breathing." Although I'd hazard a guess that this statement assumes the reader is familiar with ammonia/chlorine and their dangers, for those who fail to see the humor in that statement, I offer up the following symptoms/results of ammonia poisoning:

• At the very least, a pounding headache which will be with you all day and through the night, during which you'll get not a wink of sleep. (Personal experience after an employee mixed chlorine and ammonia thinking it'd make his chore cleaning a greasy stove easier.)
   
• Esophageal damage which may result in blood entering the lungs
   
• Throat swelling to the point of choking
   
• Drastic, immediate changes in blood pH which will damage organs
   
• Your lungs may fill with liquid pulmonary edema (and I must tell you from experience, having 'em drained is no picnic, if you survive)
   
• Permanent eye damage
   
• All kinds of blood coming from everywhere on your person. And I mean everywhere.
   
• And more!

Do be careful.

Rest assured that I'm willing to accept being called all sorts of names like "sissy" and "worry-wart" if I err on the side of being overly cautious. However, we want you to survive so that when you visit your first nodermeet we can tear the flesh from your bones and eat it raw, while we muffle your cries of exquisite agony.
 

*"Huffing": Inhaling concentrated vapors.

Ever enjoyed setting off large explosions to impress your friends? Need some way to make that moment with your significant other just perfect? Trying to disable the local power grid as part of a diabolical plan to incite cathode deprivation related misery? Then follow these simple instructions!

• Visit your local junkyard, old and abandoned buildings or heavily used overpasses: collect a large amount of Iron Oxide (rust)
• Buy some aluminum powder or, for the truly industrious proletariat, make your own with a hunk of aluminum and rough file
• Buy a few flower pots or simply 'liberate' your terra cotta brethren from the nearest landscaping store
• Find a nice and secluded high tension power line tower
• Affix several pots full of a 2:1 aluminum to rust ratio to each leg of the tower
• Insert a magnesium strip into each pot then connect each strip to a model rocket launch controller via alligator clips
• Find a safe position at least 200 feet away, preferably hidden from view and press the ignition button
• Enjoy Godzilla-like showers of sparks and arcing electricity as the tower collapses
• Head for the Canadian border as fast as possible