2H3OH + 3O2 2CO2 + 4H2O
2038 + 3 498 2 1610 + 4 928
3532 KJ/mol 6932KJ/mol
= 3400KJ/mol
Ethanol:
C2H5OH (L) + O2 (G) CO2 (G) + H2O (G)
C2H5OH + 3O2 2CO2 + 5H2O
3211 + 3 498 2 1610 + 4 928
3532 KJ/mol 6004KJ/mol
= 3400KJ/mol
Propanol:
C3H7OH (L) + O2 (G) CO2 (G) + H2O (G)
2C3H7OH + 9O2 6CO2 + 8H2O
4384 + 9 498 6 1610 + 8 928
8866 KJ/mol 17084KJ/mol
= 8218KJ/mol
Butanol:
C4H9OH (L) + O2 (G) CO2 (G) + H2O (G)
C4H9OH + 6O2 4CO2 + 5H2O
5739 + 9 498 4 1610 + 5 928
8727 KJ/mol 11080KJ/mol
= 2353KJ/mol
Pentanol:
C5H11OH (L) + O2 (G) CO2 (G) + H2O (G)
2C5H11OH + 15O2 10CO2 + 12H2O
6730 + 15 498 10 1610 + 12 928
14200 KJ/mol 27236KJ/mol
= 13036KJ/mol
Energy profile diagrams:
Methanol:
5570KJ/mol
- 6932KJ/mol
2[CH3OH] = 3[O2] 2[CO2] + 4[H2O]
Ethanol:
4705KJ/mol
- 6004KJ/mol
[C2H5OH] + 3[O2] 2[CO2] + 5[H2O]
Propanol:
13250KJ/mol
- 17084KJ/mol
[C3H7OH] + [O2] 6[CO2] + 8[H2O]
Butanol:
8545KJ/mol
- 11080KJ/mol
[C4H9OH] + 6[O2] 4[CO2] + 5[H2O]
Pentanol:
20930KJ/mol
27236KJ/mol
2[C5H11OH] + 15[O2] 10[CO2] + 12[H2O]
Obtaining evidence
Method: to carry out each experiment I will firstly need to fill up a boiling tube with 25cm³ of water to the meniscus point. I will then measure the temperature of the water with an analogue thermometer. I will then weigh the spirit lamp and alcohol on a set of scales. I will then light the wick of the spirit lamp and start the stopwatch, I will let the alcohol heat up the water by 50°C. I will then blow out the flame and weigh the alcohol immediately, I will note down the time it took for the water to rise by 50°C. I will work out the mass of the alcohol burnt by subtracting the weight before from the weight after. I will also work out how much heat energy was produced.
Boss clamp
Test tube
25cm³ water
Stand 3 cm
Wick
Heat proof mat
Fuel (spirit lamp)
Fair test: To keep this a fair test we have to bear certain aspects in mind. The beaker that the water is contained in must be the same shape each time because if it is not, the flame may have more surface area of where to heat up the water. The alcohol must be weighed accurately with scales. The alcohol has to be weighed accurately before and after each experiment. The alcohol has to be blown out immediately when the water temperature has been raised by 50°C. The thermometer must be swirled around the water before a reading can be taken. The shape of the spirit lamp must stay the same and so must the wick length. There must be a 3cm gap between the bottom of the test tube and the tip of the wick, this must be the same each time.
Safety: to ensure safety we must use goggles at all times, you should also clear the desk that you are working at. You should stand up when taking part in the experiment. You should always tuck your shirt and tie in during an experiment. You should use a splint to light the wick of the fuel, which you are using.
Diagrams
Spirit lamp:
Wick
Lid
Fuel
Test tube:
25cm³ water
Stand:
Boss clamp
Bottom support of stand
Measuring cylinder
Meniscus point
Results from experiment
Results information from experiment
Once I got all of the results information from the experiment I done, I worked out the averages. For the mass averages I worked out the mass difference for each experiment in every different fuel, I added up each mass difference, then I divided the answer by three, this gave me my answers. For the time averages I added up each experiments time and divided it by three for my answers.
Methanol:
The average for mass is 5.27 (g), I worked this out by finding the mass difference of each experiment, which are 5.14, 6.2 and 4.48.
The average for time is 8.61 (secs), I worked this out by adding the time of each experiment and dividing the answer by three, the times are 8.37, 8.41 and 9.05.
Ethanol:
The average for mass is 4.71, I worked this out by finding the mass difference of each experiment, which are 2.63, 1.66 and 1.26.
The average for time is 4.76, I worked this out by adding the time of each experiment and dividing the answer by three, the times are 5.15, 4.56, and 4.58.
Propanol:
The average for mass is 2.16, I worked this out by finding the mass difference of each experiment, which are 1.76, 0.22, and 0.18.
The average for time is 4.76, I worked this out by adding the time of each experiment and dividing the answer by three, the times are 5.48, 4.56, and 4.30.
Butanol:
The average for mass is 2.20, I worked this out by finding the mass difference of each experiment, which are 1.00, 0.85 and 1.04.
The average for time is 4.96, I worked this out by adding the time of each experiment and dividing the answer by three, the times are 5.23, 5.10, and 4.57.
Pentanol
The average for mass is 1.02, I worked this out by finding the mass difference of each experiment, which are 0.67, 0.08 and 0.81.
The average for time is 5.24, I worked this out by adding the time of each experiment and dividing the answer by three, the times are 5.26, 5.45, and 5.03.
Averages of mass and time, table
Analyzing results
The results from the, averages of time graph, shows that Methanol took the longest
time to reach 50°C. It also shows that Ethanol took the quickest time to reach 50°C.
Pentanol takes the longest to burn because it is a big alcohol, it gives off soot when
burnt, this insulates the bottom of the test tube this means that the heat can’t go
directly through the test tube because the soot is there, which blocks it, this is why
Pentanol took quite a long time to reach 50ºC.
The results from the, averages of mass graph, show that Methanol has the biggest
difference in mass when the fuel is burnt, it also shows that Pentanol has the least
difference in mass when the fuel is burnt. Pentanol is a long alcohol, which means it is
very hard to ignite, this is why Pentanol burnt the least fuel off. Where as Methanol
is a small alcohol, this makes it easy to ignite, this is why Methanol burnt the most
fuel off.
The results from the, energy release graph, shows that Pentanol has the highest
amount of nett energy. It also shows that Ethanol has the least amount of nett energy.
Pentanol has the highest nett energy because it has the highest bonds energy out of the
Four carbon atoms.
Evaluation
The results I got from my experiment were accurate enough to give me results so that
I could rely on them. I could have got more accurate results by modifying my plan for
my experiment. When I was carrying out my experiment I saw four main things that
could be improved to make the results more accurate.
1. Heat which never enters the water, because of draughts, this was due to my group
being next to the open window.
2. Heat loss from the top and sides of the beaker.
3. Heat which is not conducted by the beaker.
4. Distance from the end of the wick and bottom of the test tube may not have been
exactly the same every time.
Improvements can be made to this by insulating the sides of the beaker, using a
different material for the beaker, using a lid and providing a draught screen. We
could use a photometer, which reads how much light is given off.
My graphs I done showed some anomalous results. The Averages of time graph, had
an anomalous result, this strange result was Methanol, it was a lot more higher on the
time scale than the other four carbon atoms. This would have been due to one of the
four of number points above.