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An investigation to see how the energy is released by burning alcohols depends on the number of carbon atoms they contain.

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Introduction

An investigation to see how the energy is released by burning alcohols depends on the number of carbon atoms they contain. Planning My objective for this experiment is to find out how the amount of energy released depends on the number of carbon atom present in the various alcohols. I will use 5 different alcohols, all with different numbers of carbon atoms. The alcohols I will use are: Methanol, Ethanol, Propanol, Butanol and Pentanol. To work out how energy is released in each case, I will heat up a can fill with 150ml of distilled water by 15 degrees centigrade. Variables I will keep the same throughout the investigation I will need to keep these variables the same to ensure that this is a fair test. o The volume of water in the can. This is to be kept the same because the more water present, the more water particles there are that need to be heated up, which in turn will need a greater amount of energy. By keeping the amount of water present constant, I will see how much alcohol is needed to heat up that certain amount of water, which will tell me how much energy is needed. I will also throw out the water after each experiment and use fresh distilled water so that no excess heat is passed on to the next experiment. ...read more.

Middle

Once the temperature of the water has gone up 15 degrees, place the cap back on the spirit burner. Remove the cap after a few seconds and wipe away any condensation that had formed in it. Placed the spirit burner back on the scale and record the final temperature of the water. Preliminary Work For my preliminary work, I will decide on how much water to use and how much of a temperature increase I will allow before extinguishing the flame of the spirit burner. This needs to be established because the burner has to burn for long enough to make a significant weight decrease in itself so that the scale can measure accurately. I will use Pentanol in this preliminary investigation because it has the most carbon atoms and will therefore give out the greatest amount of heat. This is important because less of it will burn to increase the temperature of the water to a given amount, and therefore a small mass decrease will occur. I must establish a suitable volume of water that will take long enough to raise the given amount of degrees and that will cause a substantial weight loss. Run Start Temperature (�C) Finish Temperature (�C) Volume of Water (ml) ...read more.

Conclusion

I can conclude that my hypothesis was correct; methanol did release the least amount of energy per mole than any of the other alcohols. Methanol released less than Ethanol, Ethanol less than Propanol, Propanol less than Butanol, Butanol less than Pentanol. Pentanol release the most amount of energy per mole. Evaluation My method was good. I don't believe that there would have been any inaccuracies caused by the way I carried out my investigation however, my trend was weak, so there must have been a weak spot in my method. Some heat could have been lost to the surroundings, so if I were to do the experiment again, I would insult it so no heat would be lost to the surroundings. The can could still have retained heat from the previous experiment, even though I tried to cool it down. If I was to do the experiment again, I would use more than one can, and alternate them to make sure that the cans were properly cooled before I used them again. I could have left the thermometer on the bottom of the can for too long instead of stirring the water with it. This would lead to inaccuracies because the thermometer would measure the temperature of the bottom of the can, which would be higher than the temperature of the water. Ross Bowden 11RCB Chemistry Coursework ...read more.

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