Courseworks

To compare the heat output using different types of flame

In my preliminary work I decided to investigate the temperature rise per gram of fuel for three different fuels; hexamine, a wax candle and a paraffin lamp. To do this each fuel heated 200ml of water from approximately 20�c to 40�c, I then calculated the temperature rise per gram of fuel using the equation:TEMPERATURE RISE (�c)MASS OF FUEL USED (g)I used a variety of apparatus; a stand and clamp, a tin can, 250ml measuring cylinder, weight scales, thermometer, hexamine/candle/paraffin lamp and a heat-proof mat. Here are my results:SUBSTANCETEMPERATURE BEFORE (�c)TEMPERATURE AFTER (�c)MASS BEFORE (g)MASS AFTER (g)MASS DIFFERENCE (g)Wax Candle19.040.544.48643.50020.290Paraffin Lamp20.539.0151.95150.94019.802Hexamine19.534 (burnt out)10.9749.70015.699I realised from my preliminary work that the heat disperses in varies directions, the distance between the flame and the tin can containing the water can vary and the heat is lost into the room and the equipment. So taking these points into consideration I have designed an experiment to compare the heat output of a Bunsen burner.APPARATUS* Stand and clamp* Tin can* 250ml measuring cylinder* Weight scales* Thermometer* Bunsen Burner* Heat proof mat* StopwatchPROCEDURE* Set up apparatus as shown in the diagram above* Measure 200ml of water from the tap into a tin can* Place the tin can into the grasp of the clamp stand* Record the starting temperature of the water* Leave the air hole on the Bunsen burner closed* Place the Bunsen burner directly underneath the tin can* Leave approximately 5cm between the tip of the flame and the tin can* Using a lit splint turn the gas tap on full and ignite the gas, at exactly the same time start the stopwatch* Stir the water with the thermometer throughout the heating process to keep the water at an even temperature* When the water has increased by 20�c stop the stopwatch and record both the finish temperature at the time it took to reach that temperature* Place your results in a tableRepeat this procedure adjusting the air hole on the Bunsen burner by 2mm each time for 6 results until fully open.The variables that must remain constant throughout the experiment:* Volume of the water 200ml* Same tin can* The temperature raise of 20�c* The distance between the tip of the flame and the tin can* Same Bunsen burnerThe variables that must be changed are:* The position of the air holeSAFETYFor reasons of safety I must make sure that all items of loose clothing is tucked in so that they won’t catch alight, that I am wearing safety goggles when carrying out the experiment and I must always be stood up around the experiment just in case the tin can full of hot water tips over. I must also look out for possible dangerous which may occur during my experiment.FAIR TESTTo make my experiment a fair test I am going to use the same Bunsen burner, tin can, stopwatch and thermometer. I will refill the water each time from the same tap and make sure that it is roughly the same temperature; I will then wait for the water to rise by 20�c from the original temperature before stopping the stop watch. I will also make sure that the distance between the tip of the flame and the tin can is the same each time. I will repeat the experiment so that perhaps if an error occurred the first time I will know.NUMBER AND RANGE OF OBSERVATIONSI will adjust the air hole by 2mm each time for until I reach 10mm, which is fully open to get a clear spread of results. I will then repeat my experiment to make sure that all my previous results are correct and also to get a range of results.THEORY AND PREDICTIONRupert Bunsen invented the Bunsen burner in 1855 whilst he was in Germany. He decided to use a compound gas called methane. Methane is a hydrocarbon which is a compound of hydrogen and carbon, it is the simplest hydrocarbon with the formula CH4, which means it is made up of four hydrogen’s and one carbon. Other hydrocarbons are ethane, propane, butane, pentane and more. As you go down the list of hydrocarbons the amount of carbons and hydrogen’s change in the formula: Cn H2 x n + 2.The idea Bunsen had was simple: instead of mixing the gas with the air right at the point of combustion, he proposed mixing the gas with the air before combustion. This is an example of an exothermic reaction, which gives out energy, normally in the form of heat. The reaction taking place in a Bunsen burner can be illustrated by the equation:2CH4 + 3O2 2CO + 4H2OMethane + Oxygen Carbon Monoxide + WaterI predict that when the air hole if fully open, the heat output will be greatest because there is a great supply of oxygen, and where there is plenty of oxygen there is a larger reaction and the gas burns with a clear blue flame which produces the most heat.RESULTSRESULTS 1:POSITION OF AIR HOLE (mm)WATER TEMPERATURE BEFORE (�c)WATER TEMPERATURE AFTER (�c)TIME TAKEN TO RISE 20�c (minutes)Closed21.041.02:39:41219.039.02:14:03419.539.51:59:37620.040.01:57:28819.539.51:26:1510 (Fully open)20.540.51:43:35RESULTS 2:POSITION OF AIR HOLE (mm)WATER TEMPERATURE BEFORE (�c)WATER TEMPERATURE AFTER (�c)TIME TAKEN TO RISE 20�c (minutes)Closed20.040.02:07:52221.041.02:01:42419.539.51:46:58620.540.51:32:25820.040.51:15:0210 (Fully open)19.039.01:30:59AVERAGE RESULTS:POSITION OF AIR HOLE (mm)WATER TEMPERATURE BEFORE (�c)WATER TEMPERATURE AFTER (�c)TIME TAKEN TO RISE 20�c (minutes)Closed20.540.52:23:46220.040.02:08:02419.539.51:55:07620.2540.251:45:06819.7540.01:20:5810 (Fully open)19.7539.751:39:07ANALYSISFrom the graph, I can see a clear trend; as the distance in which the air hole is opened increases the heat output increases. I know this because the more open the air hole is the less time it takes to heat the water. This is because; the more open the air hole is the greater the heat output will be due to the greater supply of oxygen, and where there is plenty of oxygen there is a larger reaction occurring between the two gases. The graph illustrates that what I predicted was correct.Looking at my graph I can see that there is an anomalous result; the time taken to heat the water when the air hole is opened 8mm is less than the time taken to heat the water when the air hole was fully opened. This may have occurred due to the fact that the distance between the tip of the flame and the tin can had decreased, resulting in the tin can being closer to the tip of the flame, consequently the water heated quicker.EVALUATIONI think overall, this experiment has been successful, due to the results illustrating what I predicted and that they are theoretically correct, also I only have one anomalous result. I think that the procedure is reliable because I got a clear spread of results, however if I was to do the experiment again I would be more exact when measuring the distance between each position of the air hole. I would perhaps mark on a piece of paper the distances and then wrap it around the base of the Bunsen burner and then line up the air hole on the marks.There were various problems when conducting my experiment, these were; the heat dispersed in various directions and the heat was lost into the room and the equipment. If I was to do this experiment again I would place a piece of cardboard covered in tin foil around the experiment to contain the heat, this would prevent heat loss into the room and the heat dispersing in various directions. This would give me more accurate results.I think I collected enough evidence to draw a conclusion, I also think that I got a clear spread of results. However, if I was to do this experiment again I might move the air hole by 1mm rather than 2mm each time, this would give me more results, although I don’t think that by doing this I would prove anything other that what I have already proved.

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