Comparing the Enthalpy Changes of Combustion of Different Alcohols

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Comparing the Enthalpy Changes of Combustion of Different Alcohols


I will find the enthalpy change of combustion of a number of alcohols so that I can investigate how and why enthalpy change is affected by molecular structure of the alcohol.


I will use Methanol, Ethanol, Propanol and Butanol in the experiment. I will use these four because they should give me clear results, and they range from short chained to long-chained hydrocarbons, so patterns should be easy to spot in the conclusion.


My independent variables are

      - The type of alcohol (I will use ethanol, methanol, propanol and butanol)

My dependant variables are

  • the specific heating capacity of water
  • Mass of water in grams

…T- Change in temperature of water

My control variables are

  • The change in temperature of water- 20..C
  • The mass of water. If this were changed then all the results would be wrong, because it would take different amounts of energy to heat different volumes of water
  • The distance from the bottom of the calorimeter to the top of the wick. Otherwise different amounts of energy could escape each time making it an unfair test.
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From carrying out the follow experiment I will be able to find out the enthalpy change of each fuel I am testing. The enthalpy change of combustion of a fuel is the measure of energy transferred when one mole of fuel burns completely. I will use the fact that 42 Joules of energy are required to raise the temperature of 1 gram of water by 1 C. Enthalpy change varies according to the following conditions – temperature, pressure and concentration of solutions. Therefore I will use a standard pressure of I atmosphere, a standard concentration of 1 ...

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