To make sure the test is fair I will make sure that I have made checks on the apparatus before use. The checks will be:
- Distance between the wick and the base of the copper calorimeter: this distance will be 5cm measured using a ruler and adjusted if necessary.
- The fuel has been weighted correctly: The fuel will be weighed twice, to ensure accuracy.
- Make sure there is the right amount of water in the copper calorimeter: to make sure the correct amount of water is in the copper I will use a measuring cylinder, I will accurately fill it to 100cm. I will place the cylinder on a flat surface just to check that the measurement is correct.
- Make sure fresh water has been place in container, so that it isn’t still warm and that the copper calorimeter is also cooled down: by making sure that the water has been tipped away straight after the experiment, should hopefully be enough to make sure it will be replaced, also as we have to note the temperature of the water before we start, it should be noticeable. By adding fresh cold water it should cool the copper calorimeter.
By making sure I do these checks before I do the experiment means that I should be able to get accurate results as the test will have been run fairly and hopefully successfully as there should not of been anything gone wrong.
To make sure all the measurements are correct I will also run checks. These checks when recording the data are:
- Make sure to check the thermometer to see what temperature the water is at the start, so I am able to see what it has to be when its been heated by 10degrees. (EG, if the water was 23degrees I would heat the water to 33degrees)
- Make sure that the fuel is weighed correctly after experiment, and recorded.
By doing these checks means that all the experiments will be fun the same. This means the test will all be fair
Prediction
I think the more bonds in the alcohols molecule structure means that more heat energy will be produced when the bonds are broken and so less fuel will be used, as the heating temperature will be higher, so it will not take as long to heat. I think this will happen because there are more bonds in the large hydrocarbon, so it will take more energy to break them all. By having more energy acting on the hydrocarbon, means when the bonds are broken more energy will be released (an exothermic reaction), this reaction will heat the water. As the larger hydrocarbons release more energy than the smaller ones (I.E Methane) it means less hydrocarbons have to react to produce the same amount of heat energy, so less fuel is consumed. The smaller hydrocarbons will use more fuel because there are fewer bonds, so the bonds are broken quicker in a reaction, so less energy is needed to break them, so less heat energy is given out. This means it will take longer for the smaller hydrocarbons to heat the water, as the reaction temperature isn’t as high, so the rate of heating is less, so more fuel will be used as the water will be heating over longer period of time.
When the bonds of the hydrocarbon are broken energy is give out (exothermic reaction), this energy is used to heat the water and to remake bonds between other particles. This equation shows what products are made from reacting methane (a hydrocarbon) with oxygen (combustion):
Methane + Oxygen = Carbon dioxide + Water
CH O CO H O
The products of this reaction have smaller bond structures than Methane so the energy needed to form bonds between the products will be less. This means the energy left over will heat the water.
The table below represents the different fuels, and the sizes of the hydrocarbons.
From the data in the table you can see that Butane has the most bonds, then Propane, Ethane and finally Methane with only four bonds. So using my prediction I can work out that Propane and Butane will be the alcohols which use less fuel to heat the water. Butane will be the best fuel as it has 4 carbon particles and 10 hydrogen particles, so between them has 14 bonds which need to be broken and react, which means there will be more energy released so a higher reaction temperature.
Plan
I will do this experiment in a pair. By working in a pair, means that everything can be done faster, as the jobs can be split. This will keep the time doing the experiment as low as possible, so more time can be spent working writing up our findings Also by working in a pair, it means that some one else is also checking what happens in the experiment so that nothing goes wrong and that all the checks I have set in the ‘Variables’ are followed and completed, also the step by step instructions written below.
For this experiment I need to use:
- Spirit burner (with different alcohols in)
- Heat proof mat (To make sure the work surface doesn’t get burnt or fuel gets split on it)
- Thermometer ( to take readings, so I am able to see when the temperature of the water has risen 10degrees)
- Stand and claw (to hold the water above the flame at a accurate height)
- Splints (to safety light the spirit burner)
- Bunsen Burner (to light the splints from)
- Weighting scales (to weight the fuels before and after)
- Measuring Cylinder (to measure the exact amount of water 100cm )
- Copper Calorimeter (to contain the water during heating)
The equipment will be assembled like this:
When I do the experiment I will follow these step by step instructions to make sure the experiment is completed correctly.
- Get all the equipment out that I will need to use for the whole experiment. (listed above)
- Choose alcohol/spirit burner and place it at the base of the stand, on the heat proof mat.
- Fill measuring cylinder to 100cm with water, and pour into copper calorimeter
- Attach the copper calorimeter to the stand above the Spirit burner
- Make sure the distance between the top of the burner and the base of the copper calorimeter is 5cm.
- Place thermometer into water and note the water temperature
- While the thermometer adjusts to temperature, remove the Spirit burner and weight it on the scales. (weight the lid at the same time) Record the weight down in table.
- Place the Spirit burner back beneath the water container, on the heat proof mat. Light the wick.
- Let the temperature of the water raise by 10 c. Stir occasionally to get exact readings.
- When the water is heated, put the flame of the spirit burner out, (using the lid) and go weigh it again. Record weight down.
- Tip water away, and repeat process with different spirit burners/alcohols.
- When all the results are collected use the formula (E=mc ) to work out bond energy for all the fuels, and compare them, using graphs.
During the experiment I will measure four different things. I will measure the weight of the fuel to start with (including lid), the amount of water being used (100cm ) the temperature of the water, and finally the weight of the fuel at the end of the experiment (including lid). I will measure the weight of fuel using electronic scales. I will use these as they are very accurate, and measure to 2 decimal places, which is need, as only small amount of fuel will be used. To measure the temperature of the water I will use a thermometer, when find temperature of water, I will stir the water to make sure it is even heated. To make sure make sure the volume of water is accurate, I will put the measuring cylinder on a flat surface and look level with the 100cm mark and make sure the meniscus is just above the 100cm line. I will make sure the water has been stirred so the heat is distributed evenly through the water.
During the experiment I will be exposed to Alcohols, I will wear goggles to protect my eyes if any of the alcohols spill out the burner, and to make sure my hands are washed at the end of the experiment in case I have any fuel on them. If by accident I get fuel on my hands I will wash it off immediately. As I will be near an open flame I will make sure that nothing flammable is close, and that if working with anyone with long hair that it is tied back.
To make sure it is a fair test, the environment which the experiments will be taking place, will be the same. That each experiment will be run using my Step by Step instructions (see above) and that all measurements will be done accurately, and twice to make sure that it they are correct.
Next pages:
- Results from using E=mc
- Graph to show results.
Analysis
From the results I got fro the experiment I did, show what I predicted. They clearly show the difference between each fuel. There were very few irrational numbers in my results. The results which looked most of place was the 2nd experiment with Propane, the two results had a difference of 0.37 grams, and the 1st experiment with Butane when there was a difference of 0.48.
Evaluation
The investigation I did on the “Comparing the heat energy produced by combustion of different alcohols was successful” I think it was successful because we used detailed planning, and me and my working partner had a clear understanding with what we needed to find out from the experiment and how best to do it..
During the experiment we were able to make accurate measurements as we used the idea of measuring the fuel twice, so to make sure the electronic scales weren’t telling us the wrong weight. The method of stirring the water to make sure the temperature was even all over also helped make the experiment successful.
I think the results we recorded were correct because they showed a pattern with only a few irrational results. The results proved that my prediction was correct. They showed that butane had the highest bond energy at an average of 0.91 Kj , and then Propane 0.65 Kj Methane 0.61 Kj and final with the smallest bond structure Ethane 0.46 Kj. This means that the longer the hydrocarbons the more energy is released when combusted.
For each fuel we did two experiments, this meant we didn’t have very many results so they weren’t as accurate as they could have been, and by doing it two times it meant we were we able to see if one of the results didn’t fit the pattern of the other and realise that something must have been wrong in the experiment. But as there was no big difference or oddity in the results of the same alcohol, I believe my results reliable. The equipment I used was reliable. I had no problems adjusting it, setting it up, or dismantling, this helped keep the experiments running smoothly and with out great problems.
The irrational results I got for propane and butane, I would have liked to have redone the experiment if I had time, because there was a big difference in the results which could have changed the outcome of the whole investigation.
To improve the investigation, different fuels could be used. The fuels we used only had small bond structures. If we used fuels with longer bond structures, it would make it clearer how different sized bond structures effect heat energy to fuel consumption. To get bigger difference between the fuel consumption, you could make it for the water to reach boiling point, or 90 c. This would help clearly show the differences.
Table of results
Bond Energies
(E=mc )
E(nergy) = M(ass of water) x C(specific heat) x (Difference in temperature)
( j) (kj) 100cm (difference in weight) 10 c
Propane:-
- 100 x 10 x 0.47 = 470j (0.47kj)
- 100 x 10 x 0.84 = 840j (0.84kj)
Average) 100 x 10 x 0.65 = 650j (0.65kj)
Butane:-
- 100 x 10 x 0.67 = 670j (0.67kj)
- 100 x 10 x 1.15 = 1150j (1.15kj)
Average) 100 x 10 x 0.91 = 910 (0.91kj)
Methane:-
- 100 x 10 x 0.75 = 750j (0.75kj)
- 100 x 10 x 0.48 = 480j (0.48kj)
Average) 100 x 10 x 0.615 = 615 (0.615kj)
Ethane:-
- 100 x 10 x 0.44 = 440j (0.44kj)
- 100 x 10 x 0.48 = 480j (0.48kj)
Average) 100 x 10 x 0.46 = 460 (0.46kj)
