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Plan
Equipment: - Brick Beaker Spirit Burner
Thermometer Clay Pipe Triangle Measuring Cylinder
Tripod Matches Goggles
Method: - To begin with, I choose one out of the four different alcohols. I weigh beforehand in the spirit burner. This is so I can calculate the mass which is lost in each alcohol. The spirit burner and alcohol which I am using is on a brick under a tripod. On the tripod I place a clay pipe triangle which holds a beaker containing 100ml of water. I light the spirit burner and stir the water with the thermometer constantly. When the temperature has risen to 30ºC, I quickly place the top back on the spirit burner. Now I re-weigh the alcohol. o find out how much alcohol has been burned I subtract the finishing mass from the starting mass.
Fair Test
I will try my best to keep this experiment fair. All the variables must be controlled. These are as follows –
The scale reading has to be on zero before weighing the spirit burner and alcohol. The alcohol must be weighed accurately. During weighing the spirit lamp must be covered to avoid and evaporation of the alcohol. The alcohol has to be weighed accurately before and after the experiment. The alcohol has to be blown out immediately when the water temperature has been raised 30 degrees; it must be covered after the experiment to avoid evaporation. Any remaining carbon is to be cleaned off the beaker so that the flame can easily heat the water. Exactly 100ml of water is to be used. The length of wick on the spirit burner must be the same. The height of the burner from the beaker (the brick height) must be the same. The beaker must stay the same shape as well because if it is not the flame may have more surface area of where to heat the water. If all this is done we can ensure that we will get an accurate reading.
Safety
I will always wear safety goggles to avoid chemicals going in my eyes. All coats, bags and stools are to be kept away from the area. Hair is to be tied back and ties tucked away at all times.
Results
Practice
The practice experiment turned out rather well, and the results are similar to that of the other two experiments which I carried out after. I carried out each experiment for each alcohol twice, to be more accurate in my results.
First Set Of Results
Second Set Of Results
Percentage Error
Methanol: 249.85g – 246.86g = 2.99g 0.15
X 100 = 4.8% error
246.86g – 243.73g = 3.14g 3.14
Ethanol: 232.87g – 230.26g = 2.61g 0.07
X 100 = 0.026% error
248.82g – 246.14g = 2.68g 2.68
Propanol: 249.94g – 247.94g = 2.00g 0.05
X 100 = 2.5% error
251.96g – 250.01g = 1.95g 2.00
Butanol: 256.39g – 254.35g = 2.04g 0.03
X 100 = 0.15% error
244.11g – 241.56g = 2.01g 2.04
Conclusion
I can now conclude that the prediction I made before the experiment is correct. In my prediction I said that the amount of heat produced per gram would increase as the number of chemical bonds in an alcohol increases. This statement turned out to be true. As you can see from my graph, Propanol had the highest amount of heat produced, and this also had the highest number of chemical bonds. This is just as I had said in my prediction. Also, Methanol had the lowest amount of heat produced, just as I had predicted. So, I conclude that the most efficient alcohol out of the ones that I had investigated was Propanol, and the least efficient was Methanol. As far as I can see, there are no patterns or trends in my results
Evaluation
Looking at the overall experiment and procedure used to find the results obtained, I thought that it was a good enough way to investigate the combustion of different alcohols. The results I got were near enough of what I would have expected from the alcohols used, which I mentioned in my conclusion. The only set of results I was unhappy with was Methanol, with quite a big percentage error compared to the rest. The procedure of the experiment was good enough of finding out the energy gained from the individual alcohols, but changes could have been made to make the reliability of the results more accurate. I could have measured the amount lost after recording the alcohol temperature after about 10 minutes. These results will be really high but we'll have a greater difference between each alcohol. I do think that the results which I have obtained are reliable enough for this experiment. There were no anomalous results.
