Chemistry coursework - Fuels

Methanol CH3OH

Ethanol C2H5OH

Propanol C3H7OH

Butanol C4H9OH

Pentanol C5H10OH

Therefore I predict that Methanol will be the ‘best’ fuel, followed by Ethanol, then Propanol and the worst fuel will be Butanol.

Apparatus

Clamp

100ml beaker

Thermometer

Matches

Safety Goggles

Heatproof mat

Spirit burner

Methanol

Ethanol

Propanol

Butanol

Preliminary work

In year 7 we lit three alcohols and heated same amount of water to get the difference between the starting temperature and the ending temperature.

Plan

• Measure 50ml of water into the beaker.
• Put beaker into the clamp.
• Fill the spirit burner with the chosen alcohol.
• Put the spirit burner five centimeters under the beaker.
• Light the wick on the spirit burner
• Make sure the flame is touching the beaker.
• Wait until the temperature has risen to 40 degrees C.
• Record these results.

Fair test

Apparatus: if I changed the quantity of water in the beaker each time the results would change because with more water it would be harder to heat and with less water it would heat more quickly.  If I changed the beaker the results would differ because one beaker may be thicker than the other so the heat would not be able to reach the water as well. If I used different amount of alcohol each time the results would be different.

Techniques:

Procedure: If I changed the time that I left the spirit burner burning for then the results would differ because if I left it for longer then the end temperature would be higher and if I shortened the time the end temperature would be lower.

Analysing

I believe that the graphs and results that I have collected shows that the more carbon atoms that an alcohol has the more energy it needs to heat the water up to 40 degrees C. A different reason for the results shown above is that the molecular length becomes longer in the larger molecules and consequently increasing the surface area therefore allowing extra energy to be given off. From my graph on the next page you can see that there is a negative correlation with all of the readings following the pattern apart from Pentanol. From the results I can see that Methanol is the best gas, which is what I predicted, because it is the easiest alcohol to extract energy from and was the third quickest to heat the water up to 40 degrees C. Methanol was the easiest exact energy because it had the least amount of carbon atoms and as each carbon atoms add 15 onto the relative atomic mass then Methanol is the lightest.

Evaluation

The method I used was a good one but could have been made better if I had more time would have done the experiment a few more times to have more accurate average results. The extra time would have also been used to make sure that the water that I used was exactly the same temperature every time. I should put a layer of glass, paper, card, word or cloth to try and keep the heat focused onto the water, in my experiment some of the heat was taken away by the air. With the extra time would have also been able to do another experiment where I figure out the amount of heat given off during a suitable time period which would help me distinguish the best fuel more easily.

I believe that the method I used was a good one and the only faults are the ones listed above. Before lighting the wick I made sure that it was only two centimetres and the spirit burner was five centimetres from the beaker.

The results are probably not very reliable and are not good enough to support a firm conclusion because of all the lost heat, the starting temperature of the water not always being the same and the number of experiments that we did were too little. The only anomalous result was from Pentanol the reason I think that happened was because Pentanol has the most bonds and is therefore the alcohol that needs the most energy to break these bonds so that is why it took a long time to heat the water up to 40 degrees C.