Investigating the Efficiency of Fuels.
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Investigating the Efficiency of Fuels Introduction I am going to investigate the efficiency of two fuels. I will carry out an investigation which will allow me to see which fuel is more efficient. This is made easy because the fuels I am going to test each burn well through sprit burners. The fuels are reactive, and produce heat, therefore exothermic. You can tell this because when the fuels burn they produce heat, and when heat is produced from a reaction we call it an exothermic reaction. Energy level diagram showing an Exothermic Reaction: This shows an exothermic reaction because the products are at a lower energy level than the reactants. The difference in height represents the energy given out in the reaction. The EA is the activation energy, and this is the energy that is needed to break bonds. It is the initial rise in the energy given out in the reaction. On this energy level diagram, Delta H is negative. This is a table showing the energy required to make or break a covalent bond. Bond Energy kJ C - H 412 O = O 496 C = O 743 H - O 463 C - C 346 The bond energies are measured in kJ. Making for example, a C - H bond, releases 412 kJ of energy. This is an exothermic process, as energy is released and not required.
At this point I will re-weigh hexane and record the new weight in order to calculate the weight loss and the efficiency. Once I have tested with hexane I will do the same for pentane, and weigh it before and after the test just like I did with hexane. Before I light the pentane spirit burner, I will cool the apparatus down and re-fill the copper tin with another 50ml of water, and wait till it settles at 20°C. This way I am keeping the starting temperature the same and therefore a fairer test. Safety Equipment The experiment I will be doing involves chemicals, fire and hot apparatus. Chemicals can damage the eyes, so I will wear safety goggles when handling and testing the two fuels, hexane and pentane. As there is fire involved in the experiment, I will use a heat mat so as not to burn and catch the experiment work surface on fire. I will also tuck my tie into my shirt, and clear the work area of bags etc. Lastly, whilst working around the hot apparatus, I will take care to avoid touching it, and make people around my work area aware that some of the apparatus is hot. Whilst moving the hot apparatus i.e. the copper tin, I will use re-tractable tongs. The Combustion of Pentane and Hexane The word equation for Pentane combusting Pentane (l) + Oxygen (g) Carbon Dioxide (g) + water (l) + Heat Energy The chemical equation for Pentane combusting C5H12 (l)
When checking the temperature of the water I was boiling in each test, I used a thermometer which measured in °C to the nearest degree. The water I boiled separately with the two fuels started at 20°C and I stopped heating at 100°C. The 1 degree accurate thermometer I used meant there was only a 1 degree margin of error. This is very accurate, and means I managed to keep the test fair by only heating water from 20°C-100°C with both fuels. For both the tests (hexane and pentane) I heated 50ml of water. I used a good measuring cylinder which measured the volume of water to the nearest 1ml. Again, this is very accurate, and helped me get accurate results. Reliability I think my results are very reliable. I have bullet pointed a list of things I made sure I did in the experiment to make sure my results are as reliable as I can make them. * I blew out the flame of each spirit burner at the correct moment * I used exactly the same amount of water for each test * I trimmed each spirit burners wick so a 2cm flame would burn from each. This keeps the experiment fair * I used a wind shield to act as a draught exclusion for each test. This again ensured a fair test for each fuel * I knew that if I left a spirit burner burning for longer than it should be (still burning after water has reached 100°C) it will weigh less than it should Tom Sharp - Chemistry investigation - 11G
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