An Investigation into using Alcohol’s as Fuel Sources

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An Investigation into using Alcohol’s as Fuel Sources

Aim

The aim of this investigation is to compare the efficiency of a series of alcohols as fuels

Experimental Details

Alcohols are a closely related group of organic molecules that are capable of being used as fuel sources, for example spirit burners. One of the alcohols to be tested is ethanol which is made from fermented sugar. All alcohols belong to a family of chemicals whose general formula is C H    +   OH, with n as a whole number.

When any fuel burns it releases heat energy into the surroundings within where it lies. Therefore it is known as an exothermic reaction as it releases heat energy to its surroundings. When alcohol burns it releases two products which are carbon dioxide and water. In order to burn an alcohol you need to supply it with some sort of heat energy, the heat energy then breaks up the reacting molecules into individual atoms. Once the fuel has burnt the atoms begin to recombine to form the products of the reaction, as they recombine, energy is given out.

The four alcohols I will be testing are propanol, butanol, methanol, ethanol. In order to find out which is most efficient I will need to find out the amount of energy that is burnt. The amount of energy that is theoretically released can be calculated when a fuel burns in sufficient oxygen to produce carbon dioxide and water as they are the only products of the reaction. Some of the energy that is released is kept and recycled to keep the fuel burning. The excess energy is given out in the form of heat. Which is called the heat of combustion. 1 mole of any substance always contains an identical number of particles. When calculating the heat of combustion we use the unit kJ/mole this allows you to compare the energy released by equal numbers of molecules. A mole of a substance is its formula mass expressed in grams. To calculate the molar masses of fuels we use the atomic masses of the elements present.

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Energy is given out as the temperature of the water rises. After awhile the temp of the products falls to room temp. Heat from the reaction is lost to the surroundings. The surroundings have gained energy and the reaction has lost energy. This is called a negative reaction because of the heat change and because the total energy of the products is less than the burning reactants. The heat produced is used to heat the water in the  copper calorimeter. If we measure the temperature increase of the water we can work out the heat produced.

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