Missile Technology on the Cheap.

Step 7 The Science Bit

Alka Seltza contains two important ingredients: an acid and a carbonate.

The acid is citric acid (the stuff that give citrus fuits their bite), and the carbonate is "bicarb" - sodium hydrogen carbonate. Both of these are solids, and don't react together.

Add water, though, and they dissolve. This gives them the freedom to react, and they produce sodium citrate and carbon dioxide. Carbon dioxide, being a gas, has a much larger volume than the original reactants. Trapping the gas provides the pressure needed to work the A-S rocket.

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So, why does a matchhead make a good rocket fuel? The reason is that it carries both the fuel and the oxygen required to burn it, and the products are gaseous and are ejected forcibly from the end.

There are two kinds of friction match, the "strike anywhere" match and the safety match.

Consider the "strike anywhere" match. These are manufactured by dipping one end of a bare wooden stick into a fireproofing agent, so that it will not burn too readily. The other end is coated with paraffin, a hydrocarbon. The head of the match contains an oxidising agent, such as potassium chlorate; and a substance that is easily oxidised - usually sulphur. The head also contains a filler of clay; a binding material, such as glue; and dye to give it a distinctive colour. At the very tip is a small amount of phosphorus trisulphide, which decomposes and burns at a low temperature. This ignites the paraffin, which burns more readily because of the presence of the other chemicals. The products of combustion therefore include sulphur dioxide gas and carbon dioxide gas, which occupy very large volumes compared to the solid reactants.

Comments

[Shahe]

Wow!! Cool!! I'm gona go make bizzillions of them and fly stuff!!! And hopefully not burn anything!

[nutsandbolts_64]

and how much will you spend to get this bizzilion rockets ?

[nutsandbolts_64]

what I know the red thing is red phosphorus the binder is glycerin but I agree on the potassium chloride aww man, you just gave me an idea P.S. I hate eureka moments but it's beneficial

[chriskarr]

Are you sure that the alkali in the alka-seltzer isn't sodium bicarbonate (baking soda)?

[Kiteman]

That's what I said, except I used the modern naming convention.

[chriskarr]

Sodium hydrogen carbonate is the same as sodium bicarbonate? I realized that you wrote ""bicarb"" (excuse the double quote), but I thought that sodium hydrogen carbonate was a different substance. I just looked it up, and I guess it is the same thing. Boy, do I feel stupid. Well, at least I learned something today.

[Kiteman]

Not a problem - it's just one of those confusions between US and UK English.

[chriskarr]

Yep - similar to the whole sulfur/sulphur thing. (the only problem I have with 'sulphur' is that the 'ph' makes me think of phosphor) I wish that everybody could standardize. That way Americans and British wouldn't get confused when they work for one another on construction projects. At one point my dad told a British man that he wanted a set of standard wrenches (they had to get them from the headquarters, a few miles away) and when the British man got back the wrenches didn't fit. Sure enough they were metric. My dad asked they guy "What the hell do you think you're doing? I asked you for standard." The man replies - "Yes, this is English standard."

[Kiteman]

Ha, you can often buy double-ended spanners - metric on one end, and the closest imperial size on the the other.

[chriskarr]

Excuse me - it wasn't a wrench or a set - it was a fitting for a pipe, which was more of an inconvenience. Generally, you can make due with the wrong measure of wrenches and use the next biggest size you have. Also, he said 'European standard'. Sorry I didn't get my facts straight the first time.