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Burning alcohols.

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Introduction

GCSE Chemistry Investigation BURNING ALCOHOLS All fuels burn at different rates and release different amounts of energy depending how much fuel there is, what the conditions of the environment are and what fuel is used. An effective fuel releases a larger amount of energy for a smaller mass of fuel burnt. All of the alcohols I will be testing give off CO2 and H2O when they burn. Another way that a fuel can be considered efficient is if it combusts leaving less end products. If there are no end products the fuel has completely combusted thus making it an environmentally friendly fuel because of the lack of CO2 being released into the atmosphere. This would be considered environmentally friendly fuel. Research:- All fuels have covalent bonds. This means that they share a certain amount of electrons in their outer shell. This forms a strong bond between the two atoms. These are the links elements have with each other to form molecules. Burning and producing energy is the breaking of these bonds and the forming of new covalent bonds in the reaction product produces heat. The more dense or bonds a fuel has the more energy will be needed to break all the bonds and it will need a higher temperature. ...read more.

Middle

-The thermometer should be suspended in the water in some way because otherwise the thermometer could gain heat from the bottom of the calorimeter and produce biased results. Results:- Run 1 Alcohol Initial Temp �C of water Final Temp �C of water Temperature change �C Initial mass of alcohol Final mass of alcohol Mass of alcohol burnt Mass of water (g) Ethanol 25 39 14 149.25 148.48 0.77 100 Propanol 21 48 27 225.58 224.34 1.24 100 Butanol 25 52 27 216.31 214.79 1.52 100 Pentanol 24 54 30 201.72 200.82 0.9 100 Hexanol 23 34 11 257.27 257.07 0.2 100 Heptanol 30 89 59 235.51 233.7 1.81 100 Octanol 24 47 23 214.11 212.66 1.45 100 Run 2 Alcohol Initial Temp �C of water Final Temp �C of water Temperature Change �C Initial mass of alcohol Final mass of alcohol Mass of alcohol burnt Mass of water (g) Ethanol 26 44 18 189.04 188.02 1.02 100 Propanol 24 60 36 213.1 212.01 1.09 100 Butanol 25 50 25 223.47 222.75 0.72 100 Pentanol 20 61 41 223.3 222.15 1.15 100 Hexanol 22 82 60 231.58 230.209 1.371 100 Heptanol 23 34 11 209.78 209.56 0.22 100 Octanol 24 51 27 215.32 213.49 1.83 100 Now that I have collected the results I must find out for each run and alcohol the energy released in joules per gram. ...read more.

Conclusion

* Make the alcohol pressurised so that is burns quicker, therefore loosing less heat. However, you can never have perfect conditions in a school science lab. Professionally a Bomb Calorimeter would be used. It works in the following way. The bomb calorimeter consists primarily of the sample, oxygen, the stainless steel bomb, and water. The Dewar prevents heat flow from the calorimeter to the rest of the universe Since the bomb is made from stainless steel, the combustion reaction occurs at constant volume and there is no work Thus, the change in internal energy for the calorimeter is zero The thermodynamic interpretation of this equation is that the calorimeter is isolated from the rest of the universe. This would be the perfect as all of the problems that I identified in the original experiment are eliminated. This would mean that your collected results should be exactly the same as the expected result where no energy is wasted and complete combustion occurs. Unfortunately there is no such thing as a perfect experiment so I think our experiment was sufficient enough to deduce simple conclusions from even if the results were biased, but I had enough scientific evidence and research to understand why I was getting the anomalies and so this made me aware of how many imperfections an experiment like this can have. ...read more.

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