Science Coursework -
Energy Transfer in Fuels
Planning:
Some fuels contain more energy than others. This piece of coursework is about trying to experiment on which fuel (out of a selection) contains the most energy. In class we were shown how to work out the energy transfer from ethanol to water by quite a simple and practical experiment. We were shown how to work out the energy transfer by this formula -
Energy Transfer = Mass of Solution x 4.2 x Temperature change
Then: Mass of Solution ? Mass Change x Answer Of last Formula
The constant value of "4.2" is the specific heat capacity of water in joules per gram per degree Celsius. This is used in every formula as a constant value.
So now, I am to prepare a practical, fair-tested experiment, hopefully this is to see which fuel out of a selection contains the most energy. This experiment is to be quite similar to the class experiment, however we are testing various fuels.
We were allowed to choose from various fuels, which contained different amounts of carbon atoms, as you could tell this by the name (i.e. ethanol has two carbon atoms, octane has eight carbon atoms and so forth). As I thought it would be good and also fair to pick a selection with a pattern of carbon atoms, which all have an even amount of carbon atoms, therefore I chose -
Fuel
No. Of Carbon Atoms
Chemical Formula
Diagram Of Molecules
Ethanol
2
C2H5OH
Butanol
4
C4H9OH
Hexanol
6
C6H14OH
Octanol
8
C8H18OH
What I am about to do is, test each of these fuels for which one contains the most energy, and which will produce the largest energy transfer to water. I will do this by making the main factor initial and final masses of all four of the fuels. I will need this for the final formula. After this, I will heat the water. I will take the initial and final temperature of the water. I am to heat the water until we reach a 20?C rise in temperature. We then stop the experiment when we reach this temperature rise. We also work out the change in mass and the change in temperature in the water.
Apparatus
This is the following equipment needed: -
Method
I am to measure 100g of water in the measuring beaker and put this into the metal can. I am going to hold the metal can in place with the clamp. Then I will take the initial mass of the fuel, and record it. After this I will measure the initial temperature of the water, which I suspect will be at room temperature of around 27-28?C. Then I light the wick of the paraffin burner and make sure the tip of the flame is touching the bottom of the beaker. If it isn't, the height in which the beaker is held needs to be adjusted. Then I have to keep an eye on the thermometer to see if the temperature has risen to a 20?C rise, remembering to read it off at eye-level and not look down on it. Then, when the temperature has risen to the suitable rise, I'll stop the flame. Then I have to take the final mass of the fuel and record the mass change or difference. Using the energy formula above, I can work out how much energy was used for the experiment.
The one with the most energy will be the one, which created a 20?C rise with the smallest mass loss comparing to the initial mass loss. I will repeat this experiment for all four fuels.
Diagram
How to make the experiment a fair test:
To make this a fair test, I need to keep certain things constant or I may need to change certain things so that it will be a fair test, and each fuel has the equivalent experiment. Here is a list of how I can make it a fair test: -
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This is a preview of the whole essay
The one with the most energy will be the one, which created a 20?C rise with the smallest mass loss comparing to the initial mass loss. I will repeat this experiment for all four fuels.
Diagram
How to make the experiment a fair test:
To make this a fair test, I need to keep certain things constant or I may need to change certain things so that it will be a fair test, and each fuel has the equivalent experiment. Here is a list of how I can make it a fair test: -
Water - This will need to be constant at 100g. As different volumes of water take different times to heat up to the appropriate temperature, this will need to be kept the same for all of the experiments.
Length from flame to base of metal can - This part of the apparatus is quite important. As the tip of the flame may be of a different temperature to the base of the flame for instance, it is important that we keep the tip of the flame touching the base of the metal can. As different Paraffin Burners may have different size wicks, therefore different length flames, we shall adjust the Clamp to have the tip of the flame touching the base of the tin.
Reading Thermometer - This is very important as the thermometer should be read at eye-level as reading it from different angles the temperature may look different, and if not read at eye-level is incorrect. This is critical as we are heating the water until a 20?C rise so if the thermometer is read at the incorrect way, we may be burning off too much or too little fuel, which would then be an incorrect experiment.
Weighing The Fuel - When weighing each fuel, in the initial and final weights, the cap of the Paraffin Burner needs to be off as they may weigh different masses. This is essential for a correct answer to our formula of energy transfer.
Where the clamp holds the metal can - The clamp is made of metal, therefore it conducts heat, and so it may conduct more heat at the bottom of the metal of the can rather than the top. So for each experiment we are to clamp the metal can at the top of the container so if it does conduct heat they will all conduct around the same amount.
I will record these results in a table so if an apparent pattern occurs it will be considerably easier to see. Also by recording the results in a table, it would be easier to read off the results and produce a graph in the analysing part of the coursework.
I think my plan will be a safe one as we are using the necessary equipment to make it safe, for instance we are using a burn proof mat and safety goggles.
I believe that the experiment is a very fair one as I have stated on how to make it a fair test, this is essential for accurate results and overall an accurate experiment.
My Prediction
My prediction is quite complicated but I think that it is quite accurate. As carbon dioxide atoms in the atmosphere keep heat within the atmosphere, I think this is going to be the case for this experiment. I predict that the higher the carbon atoms in the fuel, the less fuel the water will need to reach a 20?C rise. So the higher the carbon atoms, which keep heat within the water, the less fuel will be needed for the experiment, as less of the heat will be let out for the higher the carbon atoms. This is shown in the table on the first page displaying the molecules and the chemical formula. The reason I thought of this prediction is because there is the conservational issue of "The Green House Effect". This is due to carbon dioxide atoms in the atmosphere keeping in heat rather than naturally letting it radiate out back to space. Therefore I think that Octanol (8 carbon atoms) will take the least amount of fuel to heat the water to a 20? rise.
Obtaining Evidence:
Results
The initial temperature, final temperature etc, was the same for each fuel, as you will see. As the fuels were at room temperature the all had the same initial temperature. Also we knew at what temperature we were to stop the experiment (at a 20? rise) so the final temperature will be the same as well. Therefore the temperature change is the same for all four fuels. It also shows the mass of the water.
This table shows us the masses of all four fuels in the experiment, and the mass change. This is essential for working out the most energy efficient fuel.
Fuel
Initial Mass
(Pre Experiment)
(g)
Final Mass
(Post Experiment)
(g)
Mass Change
(g)
Ethanol
09.30
08.42
0.88
Butanol
11.53
10.01
.52
Hexanol
14.25
13.53
0.72
Octanol
21.36
20.81
0.55
I think that I have made the appropriate amount of observations to prepare an accurate experiment. I have made the necessary observations such as watching the temperature the initial and final masses of the different fuels. This is all for the final formula which tells us which is the best fuel, and which fuel consumes the least amount of it to heat certain things compared to others.
For the final answer and final energy transferred this is step 1 of the formula. Here is the formula and working out of the amount of heat transferred to the water. I will be using the constant value of 4.2, which is explained on the first page. As the initial and final temperature is the same so is the temperature change. So the formula will be the same for each fuel.
=
This shows us how much energy was transferred to the water by using temperature change as the factor. Now we are to see how much energy has been transferred to the water by using the mass change. This is the final step of the formula.
Fuel
Working Out
Answer (j/g/?C)
Ethanol
00 ? 0.88 x 8400
954545
Butanol
00 ? 1.52 x 8400
552631
Hexanol
00 ? 0.72 x 8400
166666
Octanol
00 ? 0.55 x 8400
527272
The reason why we did this formula is because every fuel needed to transfer a certain amount of energy to the water to result in a 20?C rise. So this formula shows us (by using the initial and final masses) which fuel was most efficient (used up the least amount of fuel).
This shows us that Octanol gave the largest energy transfer to the water. So, my prediction was correct as I predicted that the fuel with the most carbons would create the largest energy transfer. However, the fuel, Butanol produced quite an anomalous result as this had more carbon atoms than Ethanol, which produced a larger energy transfer than Butanol. This is quite an unexpected result as we were extremely careful on making the experiment a fair test and careful on how we specified certain areas of the experiment, which we needed to be precise on. Initially I thought that the experiment was quite a successful one but it produced an unexpected result. I have recorded my results in a table as then I could see if a pattern occurred, there was not an apparent pattern. I think I have worked in a safe manner as we went by the safety precautions of tucking our ties in, placing a burn-proof mat under the paraffin burner and so on.
Analysing evidence and drawing conclusions:
I think that it will be good to represent these results in a correlation graph and then to have a line of best fit. I am aware that the graph will have the anomalous result of the Butanol.
From looking at the results on the table, you could see that Butanol produced an
anomalous result. However, on the graph I needed to incorporate the line of best fit and I had to include the Butanol result in the line of best fit as it was on the same sort of line. Therefore it looks like Ethanol is the anomalous result, which is incorrect. No apparent pattern occurred. I don't need to make any further calculations as I have already worked out the most energy efficient fuel, which is Octanol (out of the four tested). This is simply because it transferred the needed energy to the water by using the least amount of its fuel.
My results do support my original prediction overall, as the fuel with the highest amount of carbon atoms was the most efficient. However, I have also realised that industrial companies may deliberately put more carbon dioxide into a fuel, which traps in heat and furthermore does not use up any excess fuel which is also an economical factor. This thought had just occurred to me during this part of the coursework. However, putting too many carbon atoms (or another matter which contains carbon atoms) will cause much pollution therefore they must be careful on how much they put in (maybe by using catalytic converters.
Evaluating Evidence:
Overall, I believe that my experiment was quite a successful one although I was quite frustrated by the anomalous result the Butanol produced. Fortunately I didn't have to change anything in my plan whilst I was doing the experiment as I had thought the plan out carefully pre the experiment in class. I think that I did make enough observations to reach an accurate and valid conclusion, which upheld and supported my prediction in the plan. I had to make to make quite a few observations for the final formula, which included, initial and final temperatures of the water for each experiment, I had to weigh the initial and final masses of all experiments, also I had to make all the necessary observations to see if our test was a fair one. I believe my observations are reliable as I was in a group of three and all of us agreed on each observation needed, for instance we would each observe the temperature change and see if the heating of water had yet resulted in a 20° rise. There was an advantage of being in groups as sometime some of us made mistakes in reading the thermometer, as I for instance thought it had already reached a 20 degrees rise when it still had 3 degrees to go. Reading the thermometer was the hardest observation to make, as sometimes it is hard to see the mercury, which represents the temperature. So when one person read the thermometer, there would be a second opinion and then a third to agree and record it for accuracy.
I think that there weren't any odd observations at the time, and at the time of the experiment we did not notice the anomalous result of the Butanol, as we did not straight away find a huge difference in the range of numbers. I can't think of a better way to answer the original query of which fuel is the most efficient. However, I do notice that I could have made the experiment slightly fairer as, we cold have used draught excluders, which would stop any wind from blowing the flame towards another direction and this would result in the flame stop heating the water for a period of time. But, around our paraffin burner and clamp, we did not have any windows open, as we made sure that they would be closed before hand. I also made sure that the whole experiment would take place in the same position it was before as different parts of the room may have a slight temperature difference, this would make the experiment unfair.
I did get an idea for another experiment, which would be adding more carbon dioxide or carbon atoms to certain fuels and see if they become more energy efficient as carbon atoms trap in heat, therefore during the experiment less heat will be able to escape and the temperature change will happen without using excess fuel which is also more economically efficient. To do this I will need to keep the results of this experiment to compare with. As this experiment did not involve any changes to the fuels. However in the next experiment I will do exactly the same test as this one, including the same fuels but I will add carbon dioxide to the fuel before using it in a paraffin burner with a special type of apparatus. I could make the carbon dioxide to put in the fuel by producing an experiment, which will cause an exothermic reaction. Another way is by breathing out into a tube with a bung, which would put more carbon atoms into the fuel, and then I could put the lid on and start the experiment. The task, which I was set out to do, is answered by this coursework and I think answered quite well. Also my prediction was correct and out of Ethanol, Butanol, Hexanol and Octanol, Octanol is the most efficient fuel but probably the most polluting fuel out of the four as it contains the most amount of carbon atoms in it which can cause the green house effect.
