GCSE Science Coursework

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GCSE Science Coursework

Title: Burning Fuels.

What are you trying to find out? I will be carrying out an investigation, which allows me to calculate and compare how much energy/fuel is used to raise 100cmcubed of water to 20 degrees centigrade. I will be using 5 different fuels; Butanol, Pentanol, Propanol, Methanol and Ethanol. The aim is to find out how much energy is produced when burning these alcohols. Alcohol’s react with oxygen in the air to form water and carbon dioxide.  This is an exothermic reaction, meaning that when energy is put in, more energy is given off.

The formulae of the alcohols that I will be using are.
Methanol CH OH
Ethanol C H OH
Propanol C H OH
Butanol C H OH
Pentanol C H OH

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. For example Ethanol has the formula C H OH. In this formula you have five C-H bonds, one C-C bond, one C-O bond and one O-H bond. To separate these types of bonds you require a certain amount of energy, which I will show in a table.

C-H 410
C-O 360
O-H 510
O=O 496
C=O 740
C-C 350

To separate C-H bond you need to apply 410 joules of energy. There are five such bonds in ethanol so you multiply 410 by five to get 2050 joules. You do these calculations for all the other types of bonds that make up ethanol, add them all together and you get 3270 joules. All of the other alcohols can be broken up in this way. Below is a table showing the energy required to break up the bonds in each alcohol.

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Type of alcohol Energy required to break the bonds in the alcohol (j)
Methanol 2100
Ethanol 3270
Propanol 3740
Butanol 4560
Pentanol 5380


As you can see a longer molecule takes more energy to break its bonds, in this case Pentanol. Compared to a smaller molecule, methanol that requires less energy to do so. I can come to predict that the longer the molecular structure in the alcohol the more energy it will take to remove the bonds. So when I come to predicting results I can safely say that Pentanol will evolve more energy than methanol simply because it has more bonds to break.

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