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CHEMISTRY COURSEWORK THE LINK BETWEEN CARBON ATOMS IN A FUEL AND THE ENERGY IT RELEASES. PLANNING INTRODUCTION Alcohols generally belong to compounds whose molecules are based on chains of carbon atoms. They usually contain one oxygen atom, which is joined to a carbon atom by a singular bond. This makes them different to other compounds. The oxygen atom is joined to the hydrogen atom as well as the carbon atom, which makes the oxygen a part of a hydroxyl group. These atoms are generally a part of a hydrocarbon chain. These alcohols can take away water from the body, in which a hydrocarbon chain has replaced a hydrogen atom. Alcohols have a general structure of CnH2n+1OH The aim of this investigation is to see the link between the numbers of carbon atom in a fuel with the amount of energy it releases. There would be a change in the amount of energy given off that is getting greater, the more carbon atoms in the fuel, the more there are more bonds to be broken and formed, thus producing more energy. 'In a chemical reaction, bonds in the reactant molecule are broken and new ones are formed. Atoms are rearranged. Energy has to be put in to break bonds, and energy is given out when bonds are formed.' When the total energy put in is greater than the energy put out, the substance cools down (it is endothermic). This is expressed as ? +ve (delta positive). If the total energy put in is less than the energy created, then the substance warms up (it is exothermic). This is expressed as ? -ve (delta negative). I will investigate eight different alcohols using an alcohol or spirit burner, to measure the energy change during burning them by measuring the change in temperature of some water held by a container. This container must have a value of specific heat capacity so I could calculate heat transferred to it as well. ...read more.


* Repeat this procedure for the alcohols. CHOOSEN ALCOHOLS AND CHEMICAL EQUATIONS * Methanol + Oxygen ==> Carbon dioxide + Water * 2CH3OH + 3O2=> 2CO2 + 4H2O * Ethanol + Oxygen==> Carbon dioxide + Water * 2C2H5OH + 6O2 => 4CO2 + 6H2O * Propan-1-ol + Oxygen ==> Carbon dioxide + Water * 2C3H7OH + 9O2 => 6CO2 + 8H2O * Butan-1-ol + Oxygen ==> Carbon dioxide + Water * 2C4H9OH + 12O2 => 8CO2 + 10H2O * Pentan-1-ol + Oxygen ==> Carbon dioxide + Water * 2C5H11OH + 15O2 => 10CO2 + 12H2O * Hexan-1-ol + Oxygen ==> Carbon dioxide + Water * 2C6H13OH + 18O2 => 12CO2 + 14H2O * Heptan-1-ol + Oxygen ==> Carbon dioxide + Water * 2C7H15OH +21O2 => 14CO2 + 16H2O * Octan-1-ol+ Oxygen ==> Carbon dioxide + Water * 2C8H17OH + 24O2 => 16CO2 + 18H2O THE DIAGRAM OF MY EXPERIMENT Alcohols Mass of the burner and alcohol (g) Mass of the burner after burning (g) Mass of alcohol burnt (g) Mass calorimeter with water (g) Mass of calorimeter alone (g) Mass of water (g) Temperature of water finally (?C) Temperature of water initially (?C) Temperature rise of water (?C) Energy change in Kj/mol - Methanol 1st 167.57 167.25 0.32 152.43 77.21 75.22 30.10 25.90 4.20 145.17 2nd 167.24 166.98 0.26 152.51 77.21 75.30 30.80 25.80 5.00 212.91 3rd 166.98 166.70 0.28 152.14 77.21 74.93 31.30 25.70 5.60 220.44 Average 167.26 166.98 0.28 152.36 77.21 75.15 30.73 25.80 4.93 192.84 Ethanol 1st 156.83 156.61 0.22 153.54 77.21 76.33 30.70 25.90 4.80 351.54 2nd 156.60 156.42 0.18 152.36 77.21 75.15 31.10 25.90 5.20 458.94 3rd 156.42 156.25 0.17 150.67 77.21 73.46 31.40 22.90 5.50 503.41 Average 156.62 156.43 0.19 152.19 77.21 74.98 31.07 25.90 5.17 437.45 Propan-1-ol 1st 174.52 174.39 0.13 152.36 77.21 75.15 30.70 26.00 4.70 739.55 2nd 174.39 174.19 0.20 153.06 77.21 75.85 30.70 26.00 4.70 491.10 3rd 174.19 174.05 0.14 153.20 77.21 75.99 31.30 26.00 5.30 792.46 Average 174.37 174.21 0.16 152.87 77.21 75.66 ...read more.


I have a nice straight graph and no anomalous results, which is brilliant. I think these results came out well because the heat loss actually happened to all the experiments I carried out. In addition, the results are in the least reliable because there was too much heat loss. From my hypothesis, I tried calculating the energy released for each of the alcohols I planned to use and not surprisingly, the results were five times bigger than my initial results. Consequently, I went in search of results in a data book and the results I got for methanol to hexan-1-ol are as follows respectively: 715, 1371, 2010, 2673, 3323 and 3976 joules/mol-. The results also where 3 times larger than the results I got which proves that this method is a very crude way of checking out the energy released in alcohols. Then I went further to calculate the difference in the values I collected from the data book and the average difference were 652.2 while my average was 240. There is nearly three times difference between them. I also took the percentage difference of all of them and the were as follows from methanol to pentan-1-ol respectively: 69%, 68%, 66% 65%, and 64% with a total average of 66.4% this also tells me that nearly 70% of the energy released was actually lost out of the experiment from one means or another which I have listed above. This also shows my results are not reliable at all. Despite all the deficiencies in the results, my result will still says the same thing the results in the data book we says because they are affected by the same things, so they will reduce in the same way. They both proved that the higher the higher the number of atoms the higher the energy released so there surely in a link between the number of atoms and the energy released. ?? ?? ?? ?? ENAJITE JASMINE AGESE 02/05/2007 PAGE 2 ENAJITE JASMNIE AGESE 02/05/2007 PAGE 1 2 1 ...read more.

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