I think I have shown you this high speed video of a YouTube scientist igniting mixtures of hydrocarbon gases and air. He does this because it is fun, and because it shows the different energies released with different mixtures. This shuttle launch shows the incredible energy released when hydrogen is combined with oxygen. The reaction is exothermic, producing a stream of expanding water vapour that propels the rocket forwards. Fuels such as petrol (octane), are vaporised and mixed with air in a car engine before a spark ignites the mixture. The hot, expanding gas formed forces the piston up the cylinder, ultimately driving the wheels. This video was shot at high speed and then played back at normal speed, showing the progress of the reaction as it travels through the container.
Hydrocarbons are compounds of carbon and hydrogen. The simplest one, methane, is the gas we burn in the lab. It has a single carbon atom attached to four hydrogen atoms. When a molecule of methane reacts with oxygen it produces one molecule of carbon dioxide and two molecules of water.
Other hydrocarbons have different numbers of carbon atoms e.g. ethane has two, propane three and butane has four.
He only uses 30 cm3(ml) of butane in the bottle because he needs to make sure that there is enough oxygen in the remainder of the bottle to completely combust all of the butane. Oxygen is about 21% of normal air, so you need five times as much air as you would pure oxygen to achieve complete combustion.
A bottle completely full of butane would burn more slowly since not every butane molecule would be able to come into contact with an oxygen molecule. An example of this is in the video below.
The Pringles tube is completely filled with hydrogen so it burns like a candle. Air is sucked in through the hole at the bottom as the hydrogen burns until the fuel air mixture within the can is just right and it explodes.
Questions…
- The shuttle needs liquid oxygen for its fuel tanks. What must you do to gaseous oxygen to turn it into liquid oxygen?
- What is the difference in the combustion products between burning butane and hydrogen?
- How could you show (chemically) that water is produced during the reaction?
- How many carbon atoms does (a) ethanol (alcohol) and (b) propanone (acetone) have?
1 We must keep it at cold temperatures
2 Hydrogen releases its energy much faster than buthane
3 H2 + O2 = H20
4 Ethanol has two while propane has three
Thank you for another awesome post
Q1 – and if you put it under pressure it is easier to turn it into a liquid
Q2 – the question is about the combustion products, rather than the speed of the reaction
Q3 – the question means, “what is the chemical test for water?”
Q4 – excellent!
Well done and see if you can fix your answers to 2 & 3
1. Put it under enlarged but steady amounts of pressure or freeze to unreasonable amounts
2. Hydrogen – water and oxygen (released to atmosphere if not captured sufficently) and Bhutane – water and carbon dioxide (released to atmosphere if not captured sufficiently)
3. Dropping in anhydrous copper sulfate (white/transparent in colour) Turns it hydrous (blue in colour)
4. Ethanol has 2 carbon atoms and propanone has 3 carbon atoms
Q1 – increasing the pressure is good. Keep your language scientific – “unreasonable amounts” is not specific measurement. Freeze means to turn from liquid to solid.
Q2 – just water is produced because the hydrogen is reacting with oxygen
Q3 – excellent
Q4 – well done
A good effort!
cool video