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Planning - The aim of the experiment is to work out the enthalpy change of combustion of a fuel.

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Introduction

THE TASK The aim of the experiment is to work out the enthalpy change of combustion of a fuel. BACKGROUND INFORMATION In an exothermic reaction, energy is given out to the surroundings, usually in the form of heat and is usually shown by a rise in temperature. In an endothermic reaction, energy is taken in from the surroundings, usually in the form of heat and is usually shown by a fall in temperature. During a chemical reaction, old bonds are broken and new bonds are formed. Energy must be supplied to break existing bonds. Therefore, bond breaking is an endothermic process. Energy is released when new bonds are formed. Therefore, bond formation is an exothermic process. This shows an exothermic reaction because the products are at a lower energy than the reactants The difference in height represents the energy given out in the reaction. ...read more.

Middle

A hydroxyl group: They have the general formula: CnH2n+1OH The structures of the 5 alcohols I will be experimenting with: Methanol: Ethanol: Propanol: Butanol: Pentanol: SECONDARY SOURCES Chemistry for GCSE - E.N. Ramsden CGP Chemistry Revision Guide - Richard Parsons Class notes http://www.bbc.co.uk/education/gcsebitesize/ http://www.revise.it/ PRELIMINARY WORK The loss in mass of methane was measured, after heating 50cm� of water until it went up by 20�C. It was found that the temperature rises by 20�C very quickly, meaning that the results would be less accurate as there is a smaller degree of error. Therefore I decided to measure a temperature rise of 30�C instead. I thought that using 50cm� of water would be fine. EXPERIMENTAL PREDICTION I predict that the more bonds there are holding the carbon, oxygen and hydrogen atoms together; more energy will be required to break them apart. ...read more.

Conclusion

Then, the spirit burner was placed 15cm under the copper beaker. The thermometer was then inspected until the temperature of the water had risen exactly 30�C above the starting temperature. The spirit burner was then weighed, and the change in mass was noted down. Accuracy: * Make sure you read the thermometer at eye level. * Make sure that the size of the wick is roughly the same size in each experiment. Safety: * Make sure that the wick of the spirit burner does not fall into the alcohol while it is on fire, as it will cause an explosion. * Make sure that you wash your hands if you come into contact with any of the alcohols, as most of them are toxic. * Make sure that the thermometer and the copper tin is firmly clasped into the clamp-stand, as it could cause damage to the thermometer, or injury to you if one of them falls off. ...read more.

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