Make a Ballistic Bubble Machine
9 Steps

## Step 9: What's going on?

In the heart of the machine, an electric current splits water molecules (H2O) into the two elements that they are build of: Hydrogen (H) and Oxygen (O). These elements will form H2 and O2 molecules, which escape from the water in bubbles.
The funny thing is, that when the hydrogen and oxygen-bubbles are put together again, they won’t re-unite into water-molecules all by themselves. They must be given a little ‘push’ to do that. When 'pushed' (for instance with a spark or a flame), oxygen and hydrogen will bond again as water-molecules, with a loud crack and some heat as a thank you.

Rocket fuel
The heat that is produced when hydrogen and oxygen are combined to water, makes rockets launch. The large clouds that appear when rockets launch, are made of pure and plain water. The large tanks that are mounted under the space shuttle contain hydrogen and oxygen seperately. So, somewhere at Nasa, there must be a BIG Ballistic Bubble Machine.

Q's and A's, from the top down
There's a lot to tell about what's happening when cracking knalgas-bubbles. The questions and answers below are a sort of cascade: The answer to the first question gives rise to another question, and so on...

Q: Where does the crack come from, when the bubbles are lighted?

A: What happens during the crack is an extermely fast reaction between one oxygen (O2) molecule and two hydrogen (H2) molecules. During this reaction, two water-molecules (H2O) and energy are formed. The energy that “emerges” during the reaction causes the crack you hear.

In shorthand, the reaction looks like this:
1 O2 + 2H2 → 2 H2O + energy

In a picture, it looks like pic numer 3.

Q: Why is the reaction so extremely fast, then?

A: The reaction can happen so fast, because in the gasbubbles there is exactly one oxygen molecule present for every two hydrogen-molecules. So after the reaction, there will be no oxygen or hydrogen left. Such a mixture of gasses is called a stoichiometric mixture. In dutch, it's called an "explosive mixture".

Q: So where does this "explosive mixture" of hydrogen and oxygen come from?

A: The oxygen and hydrogen come from the water inside the jar. Water is a "compound" of two atoms hydrogen and one atom oxygen: H2O. In the jar, the water-molecules are decomposed into hydrogen and oxygen. There will be twice as much hydrogen as oxygen, because water contains two hydrogen-atoms and only one oxygen-atom.

Both hydrogen and oxygen are gasses at "normal" temperatures, so they form bubbles of gas that escape the jar through the tube.
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Wyle_E says: Jan 9, 2011. 9:55 PM
Actually, those two white cylinders on the space shuttle are solid-fuel boosters. The liquid oxygen and hydrogen tanks are in that fat brown cylinder in the middle.
Most of that huge cloud around the pad isn't from the main engine exhaust, it's cooling water that keeps the steel blast deflector in the flame trench from evaporating like a snowflake.

Back to electrolysis: I've used lead electrodes. Lead is easy to come by, is inactive enough not to be corroded, and you can solder wires to it.
pyrorower says: Jun 25, 2011. 1:30 PM
I think there is a detail or two you are forgetting. I have run this reaction quite recently and found that the products aren't oxygen and hydrogen, but rather are hydrogen and chlorine gas. Since this is an aqueous solution of NaCl, the current splits the water, and some of the chlorine binds to the lead, forming insoluble PbCl2, which sinks to the bottom. The rest of the chlorine is released as a gas. Without any chlorine to bind to, the aqueous sodium bonds to a hydroxide ion from the water, and the extra hydrogen is released as a gas at the other electrode. So I personally would not recommend using lead electrodes to do this.
I just checked, and a good option would be to use baking soda instead of NaCl and if you do, then you could stick with using iron or steel. I used a setup like this once to power my own version of the water-bottle rockets :)
rjbatc says: May 8, 2012. 12:29 PM
But people say you should not use Stainless steel either, because it releases hexavalent chromium into the water.
pyrorower says: May 10, 2012. 2:14 PM
While that is normally a valid point, I believe it is not a concern in this particular scenario for a few reasons. First, if you use baking soda as the electrolyte in this reaction, the steel should not be corroded while it is used due to the composition of the baking soda. Second, even if it were to in fact be corroded by the reaction, I doubt that any of the chromium compounds would find their way into your body unless you ingested one of the fluids simply due to how the cell is constructed. The chromium would be in liquid state and thus when the gas passes through the tube into the cup, the aqueous chromium would be left behind in the cell. Therefore, while chromium compounds can be given off by steel used for electrolysis, I believe that given these circumstances it is not something to be concerned about.
f.3 says: Sep 6, 2012. 6:26 PM
That's great and all and you seem to know your stuff. What though, should one do to dispose of any contaminated water solution? If it has chromium in it and you put it down the drain even at a small amount, isn't that like poisoning the well in a way? If you dump it outside I know you risk poisoning ground water, your pets or other wildlife and or your garden. So again what do we do with the stuff after the project is over?
_Scratch_ says: Mar 9, 2011. 3:37 PM
Yea, the middle tank that has the oxygen/hydrogen in it is what fuels the space shuttle boosters.
ynze (author) says: Jan 10, 2011. 1:00 AM
Thanks for correcting the mistake! I'll write it down better in the I'ble as soon as I find time.

Could you post a pic of the lead electrodes in action?

Thnx again.

Ynze
Wyle_E says: Jan 10, 2011. 8:16 PM
I didn't take any pictures. It was decades ago, for a middle-school project.
dombeef says: Jan 2, 2011. 1:22 PM
The mushroom and one up ornament, the mushroom in the second picture in step 4 is the contest
ynze (author) says: Jan 2, 2011. 4:23 PM
Sorry dombeef, someone else was ahead of you :-)
dombeef says: Jan 3, 2011. 7:01 AM
Oh, ok