Combustion of Alcohol's.

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Combustion of Alcohol’s

        When alkanes burn, an exothermic reaction takes place; energy is released as heat. Energy is needed to break the bonds on the left-hand side of each equation. However, once they have been broken down, they are then reformed and this process gives out energy as heat. The aim of our experiment is to find out which alcohol, when burnt, gives out the most energy. We are going to do this by burning different alcohols below a test tube of water. We will wait until the water has risen from 25°C to 80°C and will calculate the mass of alcohol that has been needed to create this temperature change. We will weigh each alcohol before and after each experiment.

        In my preliminary work, I was able to work out the average amount of energy given out by each alcohol when burnt. Using the bond energies of each type of bond, I was able to work out the energy needed to break the left-hand side of the equation, and the energy created when forming the bonds on the right side of the equation. To the right hand side, I also had to add the extra amount of heat evolved when the water formed on the right hand side condensed into liquid. With the totals on each side, I then had to subtract the right side from the left. The table below shows the results I got from this preliminary work.

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The negative sign before each overall heat change shows that the energy was released, exothermic.

        From these results, I can see that Pentanol gives out the most energy when it is burnt, and Methanol releases the least. Using these, I can make a prediction. If Pentanol releases the most energy, then compared to the others, it should take the least amount of mass of alcohol to heat it. Likewise, Methanol releases the least amount of energy, so it will use more mass to heat the same amount of water.

        To make sure that my experiment is as fair ...

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