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# How does the Heat Energy given out during the Combustion of Alcohols Change as the Carbon Chain of the Alcohols used is increased?

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Introduction

How does the Heat Energy given out during the Combustion of Alcohols Change as the Carbon Chain of the Alcohols used is increased? Aim My aim for this investigation is to find out how the heat energy released during the combustion of alcohols change as the carbon chain of the alcohols is increased. I will be using the following equation for the reaction to take place: Alcohol + Oxygen Carbon Dioxide + Water I will be substituting the alcohol with the following: * * Pentonal * Ethanol * Propanal * Butanol * Methanol I will also be using the formula below to work out what ?H is: ?H = Mass of Water x Specific Heat Capacity of Water x Temperature change Background Knowledge In Chemistry, there are two terms that mean giving out energy and taking energy in. These two terms are Exothermic and Endothermic. Exothermic is a reaction that gives out energy, normally in the form of heat. ...read more.

Middle

when Bonds are Made Endothermic Reaction: Apparatus Alcohols: Ethanol Methanol Pentanol Butanol Propanol Timer Aluminium Tin Thermometer Water Beaker Tripod Stand Method 1. Set up apparatus as shown: 2. Use a beaker to measure the correct quantity of water. 3. Place water in tin and take temperature. 4. Get first alcohol and weigh. Record and then burn for time stated. 5. Take temperature at end and the weight of alcohol. 6. Replace tin and start at step 2. Prediction I think that in the main experiment, the alcohol with the longest carbon chain will give out a lot more energy. Methanol Energy required to break bonds = +2806.5 kJmol-1 Energy released when bonds are made = -3343 kJmol-1 ?H = -539.5kJmol-1 Pentanol Energy required to break bonds = +10476.5 kJmol-1 Energy released when bonds are made = -13018 kJmol-1 ?H = -2541.5 kJmol-1 Here is a hypothetical graph of what I think my final graph should look like: Preliminary Work In class, we did preliminary work to calculate correct volumes and time. ...read more.

Conclusion

I also checked that my results were precise by repeating the experiment again. I then used those results to make an average of the previous results and then used the averages to make my graph. As you can see, the results in my preliminary work match my main results; this is also followed by the hypothetical graph in my prediction, which also matches my results. If I were to do the experiment again, I would improve it by doing the following things: The results that I got were quite accurate, as we did the experiment 3 times. From these results, I then took an average. This is what I recorded on my results table. The procedure was quite complex, and in my group we decided to use a draft excluder. These prevented a draft moving the flame away from the tin can which could change the results that I got. * Work in a larger group, not just two people so that the experiment would not have as many timing limitations. * Use more than 4 alcohols (Pentanol) Shaun May 11C: 9083 Chatham Grammar School for Boys: 61201 ...read more.

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