Volume of water, mass of fuel, temperature of water, height of tube, height of flame, type of fuel, time it takes, width of flame, colour of flame, material of container, size and surface area, purity of fuel, heat loss and shape of type of wick.
The type of fuel, heat loss will be the variables to change.
We will measure to control the temperature of the water using a thermometer, time it takes using a stopwatch, mass of fuel using a scale, purity of fuel and the material of container.
Hypothesis:
I predict that hexane will be the fuel that releases the most energy per gram because it has the highest theoretical values for energy per gram since it has the most bonds then any of the other four fuels we are using (methanol, ethanol, propanol, butanol) so it has the most energy stored in it so it should have the most energy released when combusted.. I think that hexane will release proportionally around x2 energy per gram compared to methanol because methanol has a theoretical value of 17000 J/g and hexane has a 35000 J/g theoretical value and 35000/17000 = 2.059.
Apparatus:
Stopwatch, five containers containing the five fuels we will be using (methanol, butanol, ethanol, propanol and hexane), thermometer, boiling tube, clamp and stand.
Preliminary experiment discussion:
We did three preliminary experiments to find out what is the most accurate method to do this experiment, and by more accurate I mean to get a number that we feel is the closest number we will get to the theoretical values. The first time we agreed that 3 minutes of heating would be enough keeping in mind that if we heat the water for too long, a lot of energy would be lost. We also agreed on that the bottom of the tube be 15 cm away from the container. The second attempt we changed the length of the distance between the bottom of the tube and the container to 10 cm and our result was a lot more accurate. The third attempt we decided to make the distance between the bottom of the tube and the container to 7 cm and we changed the time to heat 2 minutes and a half instead of 3 minutes to make the result even more accurate. We wanted to put tiles around the container to decrease the amount of energy lost in the atmosphere but we did not have time.
Method:
1. Measure 40 cm³ of water in a measuring cylinder and place the water in a boiling tube and clamp the boiling tube to a clamp and stand. Then measure the temperature of the water and record it.
2. Bring the container that is wanted and measure the mass of the container without the top and record the number given. Then place the container underneath the boiling tube and measure out a distance of 7 cm between the bottom of the boiling tube and the top of the wick of the container.
3. Light the wick and start timing using a stopwatch. Wait for 2 and a half minutes then blow out the wick and record the current temperature of the water. Then measure the mass of the container without the top on and record.
4. Calculate the change in temperature of the water and the change in mass of the container and use these digits and previous ones to work out the amount of energy released per gram.
5. Repeat with each fuel (methanol, ethanol, butanol, propanol and hexane) twice to find out which fuel is the one that releases the most energy per gram.
Diagram:
Results:
Analysis:
We found out that Butanol released the most energy per gram with an averaged of 9607J/g.
My prediction is in fact correct but we did not do the experiment accurate enough but we know that we were close because butanol the second highest fuel came first but we did very badly on our hexane experiments. We did not expect our hexane results to be so low. This is because when we did the hexane experiments we had a problem since once the water was boiling violently and was spilling out of the boiling tube we had to stop the experiment only 1 minute and 7 seconds after we lit the wick of the container and the other try the container lost too much weight compared to other people’s results so since the difference in mass was higher, we had to divide the number we had for energy by a high number making our energy released per gram a very low number.
Hexane is in fact the fuel that releases the most energy per gram because it has the most bonds than any of the other four fuels (methanol, ethanol, butanol, propanol) therefore it has the most energy stored in it, so when it was combusted, we broke these bonds causing all that energy to be released. Butanol released more energy per gram than propanol and propanol did in fact release more energy per gram than ethanol and ethanol did do the same for methanol, which was expected from our theoretical values and according to the amount of energy stored from the amount of bonds in each fuel. So our pattern was close to being 100 percent right.
Evaluation:
I would say that we did do this experiment relatively well since 4 out of the 5 fuels came in their right places but we got awkward results from our hexane experiments causing our pattern to alter than what was expected.
I think our experiment is not accurate enough because our fuel that was supposed to come first came before last which is very bad and since we were expecting in to be around 10000 J/g higher than our actual result. We had of a couple of anomalous results in our experiment which were our first try of propanol since it went over 100º C so too much energy was wasted but we managed to do another two tries that were only 2 minutes long instead of 2 minutes and a half so we now ignore that result. That result was too high compared to the other two tries which were in the same range. Also our third try in our methanol experiments was too low so we just ignored it and used our other two tries which were closer to methanol’s theoretical values. Another anomaly was the second try of our ethanol experiments which was way too low compared to the other one so we repeated the experiment and got a try that was closer to our first try which was about 36.5 % of the theoretical value for ethanol, which we found very accurate. And of course both our hexane experiments were very inaccurate meaning they were only about 16.92% of hexane’s theoretical value. I think our good results (excluding the anomalies) for all fuels except hexane were very reliable because of their closeness to their theoretical values, but we include the hexane experiments, our results are not very reliable.
We could have done better by using tiles to surround the flame from the containers to preserve so of the heat lost in the atmosphere and we could have done more preliminary experiments to find out the best way to attempt this experiment but we did not have enough time. We also could have picked a constant time of heating for all experiments because we had some occasions where we had to change the time of heating since the water was boiling or just went to high or too low compared to the theoretical values and our other tries.
