Methanol, the common antiseptic in rubbing alcohol, is very flammable. This comes in handy! This lab will use methanol vapors to create a fireball and simulate the mechanics of real rocket engines. We will use a 5-gallon water cooler bottle to house our fireball so that the exhaust out of the top will generate trust. This lab is a bit dangerous so don't? partake unless you're rather foolhardy.
Methanol is very dangerous, and therefore, should you come across it when using rubbing alcohol is should be very diluted. The rubbing alcohol sold in most drug stores is over 90% isopropyl alcohol; however, for the purpose of this lab standard rubbing alcohol will do just fine.
Going back to methanol though, it has a very acute risks, they include:
Poisonous by ingestion or inhalation, may cause
respiratory
failure, kidney failure, blindness. Be careful! The main reason we
want to use it though is for its flammability. Methanol is sometimes
used in internal combustion engines. Methanol is the fuel of choice
for drag racers and other open wheel racing. They use it as fuel for
remote controlled model airplanes, as well as for antifreeze, and it
can be converted into formaldehyde to create various plastics. For
an example of methanol burning click on the video to the left.
The chemical equation for the combustion of methanol is: 2CH3OH + 3O2 → 2CO2 + 4H20
To create the fireball we took VERY LITTLE methanol and poured it into the container. It should be enough to barely cover the bottom of the container (i.e. in the container its depth should be no more than 1 cm or so). Then we should the bottle and made sure to get most of the methanol on the sides of the bottle. At this point the bottle is full of methanol fumes, if you want proof just smell it! Anyway once the bottle is ready, remove the top and light it from the very top of the lid. Do not place your hand over the bottle; you will lose your hand! We recommend using a longer grill lighter so you are at a safer distance. Once the top is on fire it will spread inside creating a fireball. As the temperature soars the gas will expand tremendously. Burning gas will shoot out of the can and you will have the force needed to propel a rocket. This is the premise of rocketry (using liquid fuel). Both model rockets and NASA also use solid composite fuels. Below is a series of photographs documenting one second of time:
Next is a series of two movies documenting this process. The first one (left) is a closer slow-motion shot of the fireball being created and expelled and the second (right) shows from further away the length of the fire column created by the exhaust.
The lab worked. When we filled a regular bottle with methanol the vapors combusted to create a large fire column, which while leaving the contained created enough thrust for it to theoretically move a certain distance. If there were a steady stream of fuel and an ignition system, we could have made a rocket, or could we? We found out that fuel and ignition is not enough, just like in a car, you need something extra. We turned to the equation again:
2CH3OH + 3O2 → 2CO2 + 4H20
We were missing oxygen! It was clearly there. When we burnt the fuel the first time it used all of the oxygen in the container, and it never filled back up. Therefore we had to pump the bottle with air again! Once we did the test worked again; however, without oxygen there can be no fire. Therefore, for there to be any possibility of creating a rocket, along with constant fuel, we would need constant air. Maybe next time!
Finally, here is a video of lighting an airless container. If you notice if catches on fire. That is not the vapor though. The methanol left on the bottle caught fire and we actually melted one of our bottles, oops!
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If you have used any of this information or any of these images
please go ahead and cite them in your bibliography. For your convenience,
this is what the citation would look like in MLA format:
Family, Afrooz. “Methanol Bottle Rockets.” May 16, 2005 Mad Physics. dd mmm. yyyy †
<http://www.madphysics.com/exp/methanol_bottle_rockets.htm">
We are glad to share our knowledge with you as long as you cite all of our info, and contact us before you use anything for non-educational purposes (commercial, etc.).
† In the bibliography you must insert the day you visited the site (this is relevant because the site could change at some point), therefore, in the bibliography above replace dd with the day you visited, mmm with the abreviated month, and yyyy with the year (ex: dd mmm. yyyy becomes 23 Dec. 2004).
