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Investigating the Heat Of Combustion of Different Alcohols

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Investigating the Heat Of Combustion of Different Alcohols Introduction In this experiment I will be testing to see if certain types of alcohol give of more heat combustion than others. A fuel is a material with one type of energy which can be transformed into another sable form. Alcohol is an organic compound in which a hydroxyl group is bound to a carbon atom. Combustion is the reaction between a fuel and oxygen that produces heat (and usually light). Background Knowledge The formula for combustion is: Alcohol + Oxygen Carbon Dioxide + water + energy CH3OH + O2 CO2 + 2H2O + energy The energy to make or break a chemical bond is called the bond energy and is quoted in KJ/mol of bonds. We measure heat in degrees Celsius by using a thermometer. Different alcohols have different amounts of carbon bonds. The more carbon bonds, these alcohols have, the more energy is released when they are burnt. Preliminary Experiment Aim I am going to investigate the heat combustion of fuels and use the results to plan an investigation. The independent variable that I will change will be the type of alcohol. I will record how much weight is lost in each alcohol to identify how much energy is used. The alcohols I will use are:Methanol, Ethanol, Propanol, Butanol and Pentanol. ...read more.


Variables: The independent variable that I will change will be the type of alcohol. The variables I will keep the same are: * The volume of water- by using a measuring cylinder to measure out 50mls of water each time. If I don't it could be heated up more quickly or slowly. * Size of Container- by using the same container each time. If I don't it could affect how quickly the water gets heated. * Temp. of water- I don't have to keep this the same as long as I always measure the starting temperature and when it rises by 20o blow the spirit burner out. * Temperature- by doing it in the same room each time. If I changed to a different room the temperature might be hotter or colder and affect the experiment. * Time- I won't time the experiment but I will heat the water until it rises in temperature by 20o and then weigh the alcohol again. Equipment: * Steel container - to put the water in. * Thermometer - So I can measure the temperature of the water. * Spirit burner - To burn the alcohol and see how much weight is lost. * Measuring Cylinder - To always have the same amount of water. * Stand - To hold the container, with water in, above the spirit burner. ...read more.


I chose a scatter graph because there can only be one amount of carbon bonds in each alcohol. The graph shows that the more carbon bonds there are the more energy per gram there is. This confirms my prediction. The graph shows a positive correlation between the number of carbon bonds and the amount of energy per gram. This is because each carbon bond when broken gives off energy and therefore the more carbon bonds you have the more energy per gram you have. I think that either the results for Butanol or Propanol are incorrect. Butanol has one more carbon bond than Propanol but the results I recorded show that they have the same amount of energy per gram. Evaluation: I think my methods of collecting the data were accurate because I collected each alcohol three times and then got an average. My graph is quite accurate apart from Propanol and Butanol which were odd because they were the same energy per gram when Butanol should have been more. I could have improved the accuracy of my experiment by using extra equipment so that I wouldn't lose any energy into the atmosphere. I think that the odd results happened because either the water temperature did not rise by 200 or more likely that I used the same alcohol without realising. Overall I think the investigation went well but it could be improved on next time by finding a way to stop the loss of energy. ...read more.

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