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Investigating factors affecting the heat of combustion of alcohols.

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Introduction

Robert Stewart Investigating factors affecting the heat of combustion of alcohols PLANNING SECTION Introduction Alcohols are organic substances, and consist of Hydrogen, Oxygen and Carbon. All alcohols are toxic but the amount that can be tolerated by the human body varies for different alcohols. For example drinking small amounts of Methanol can lead to blindness and even death. Ethanol is the only alcohol that can be drunk safely and is found in all alcoholic drinks. Throughout this investigation I am going to investigate to different factors that affect the breakdown of an alcohol. e.g. Methane (HCO) + Oxygen (O2) Carbon dioxide (CO2) + Water (H2O) Aim I am going to investigate increasing the chain length and see what effect there is on the heat of combustion. Preliminary Work The point of preliminary work is to find out what things that I should vary and keep constant. For my preliminary work I used computer software called Focus Science Investigation 2. This software enables you to simulate experiments. This means that I am able to quickly carry out experiments to help in planning for my investigation. Alcohol Temperature Increase (oC) Mass of burner before exp. (g) Mass of burner after exp. ...read more.

Middle

I am only changing the quantities however I believe that there will be linear relationship between the number of CH2 sections and the amount of energy released per mole of a certain alcohol. The same bonds will release the same amount of energy, this means that each CH2 section releases the same amount of energy. However it will not be directly proportional as it to go throguh zero on the graph. If it was zero it would mean that no energy was given off from the reaction. OBTAINING EVIDENCE SECTION Changes to Plan There are no parts of the plan that I think that are necessary to change, as I am satisfied with my plan. Results I have put my results into a table, which can be seen overleaf. I have also calculated the enthalpy and added this column into the table. I have put all my results to 3.s.f. I have shown an example of how I worked out the combustion of heat. I am going to take the first result for methanol. Temperature change (oC) = 14 Change in mass of alcohol (g) = 1.10 Specific heat of water = 4.18 Heat evolved (J) = Temperature change (oC) ...read more.

Conclusion

There is little I can do to stop the soot forming, however at the end of each experiment I could wipe off the soot which had formed with a damp cloth to reduce the possibility of this effecting my results adversely. If I were caring this out again, I would just have to make sure that the spirit burners' wick were all the same surface area. Further Work To provide further evidence about the link between concentration and the enthalpy of alcohols I could do the following. I could use different alcohols. Instead of investigating the affect of increasing the length of the chain, I could investigate the position of the O-H section. I could do this by using other alcohols such as Propan-2-ol, Butan-2-ol and Pentan-2-ol comparing them to Propan-1-ol, Butan-1ol and Pentan-1-ol. I could calculate the heat of reaction, and then compare it with data book values. This would allow me to calculate the percentage errors. I could change the constants and variables in such as seeing the effect by varying the distance between the spirit burner and copper can or volume of water. I could even investigate this experiment with another substance and not water and compare the results. I could also look up more information from the Internet. There are websites that have sample data that could be useful towards my investigation. ...read more.

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