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Find out the amount of energy released when burning different alcohols.

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Introduction

Chemistry Coursework - Combustion of Alcohols Aim: To find out the amount of energy released when burning different alcohols. Hypothesis: I predict that octan-1-ol will release the most heat energy. This is because there is more bond energy in that molecule than the other alcohols. Within a molecule there are bond energies that are holding the atoms together. When the fuel combusts a chemical reaction takes place, this breaks the bonds, this requires energy, and makes new bonds this gives out energy. The energy differences between the two tell us how much energy was given out or taken in. We can show this on a graph. Planning: In this investigation I will be burning alcohols to heat up a can of water. I will be burning seven alcohols, Ethanol, Propan-1-ol, Butan-1-ol, Pentan-1-ol, Hexan-1-ol, Heptan-1-ol, Octan-1-ol. The aim is to find out how much energy is produced when burning these alcohols. 'An alcohol is a series of organic homologous compounds, with the general formula Cn H n + 1OH�. Alcohols react with oxygen in the air to form water and carbon dioxide. The reaction that is involved in burning alcohols is exothermic because heat is given out. ...read more.

Middle

The alcohol has to be blown out immediately when the water temperature has been raised 30 degrees; it must be covered after the experiment to avoid evaporation. The thermometer must be swirled around the water before a reading can be taken, this insures that you are measuring the temperature of the whole water not just the bottom of the can. The shape of the spirit lamp must stay the same and so must the wick length. If all this is done we can ensure that we will get an accurate reading. Method: * Record initial mass of alcohol plus burner, this is so that at the end of the experiment the alcohol and burner can be measured to get the results. * Measure out 100cm3 of water in to the copper can using measuring cylinder. * Stir and record initial temperature of water, so you can calculate the amount of temperature rise later. * Start clock and light burner at the same time, so the timing of the experiment is exactly right. * Place can so flame is 3 cm from the bottom of the it, * Stir water, so the temperature is spread among all of the water in the can. ...read more.

Conclusion

Since heat is given out when bonds form, less energy is given out by incomplete combustion. So this is why it affects the outcome of the experiment. To make this problem irrelevant I could have made sure a constant supply of oxygen was present in the experiment. Fuel Initial mass of alcohol Final mass of alcohol Mass burnt Temperature of water before Temperature of water after Temperature rise Ethanol 221.59g 220.24g 1.35g 23�C 37�C 14�C 219.49g 218.36g 1.13g 23�C 36�C 13�C 218.03g 216.71g 1.32g 23�C 35�C 12�C Propan-1-ol 182.82g 182.57g 0.3g 20�C 40�C 20�C 182.22g 181.61g 0.61g 21�C 34�C 13�C 181.57g 180.57g 1g 21�C 55�C 14�C Butan-1-ol 208.35g 205.20g 3.15g 25�C 37�C 12�C 205.20g 202.86g 2.34g 23�C 32�C 9�C 202.86g 200.59g 2.27g 21�C 30�C 9�C Pentan-1-ol 211.89g 210.20g 1.69g 20�C 30�C 10�C 210.30g 208.29g 2.01g 20�C 28�C 8�C 208.29g 206.81g 1.48g 21�C 27�C 6�C Hexan-1-ol 216.84g 214.61g 2.23g 20�C 30�C 10�C 214.61g 212.81g 1.8g 30�C 43�C 13�C 212.81g 210.81g 2g 21�C 34�C 13�C Heptan-1-ol 207.8g 206.95g 0.85g 22�C 40�C 18�C 206.95g 206.36g 0.59g 19�C 36�C 17�C 206.36g 205.87g 0.49g 20�C 36�C 16�C Octan-1-ol 222.09g 220.50g 1.59g 20�C 30�C 10�C 220.50g 218.74g 1.76g 28�C 30�C 2�C 218.74g 217.20 1.54 37�C 40�C 3�C Graph of averages: Averages: 1. 13 2. 15.6 3. 10 4. 8 5. 18.6 6. 17 7. 5 ...read more.

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