Comparing fuels

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Comparing fuels

Plan

In this investigation I will be burning alcohols to heat up a test tube of water. I will be burning five alcohols, methanol, ethanol, propanol, butanol and pentanol. The aim is to find out how much energy is produced when burning these alcohols. Alcohols react with oxygen in the air to form water and carbon dioxide. When hydrocarbons are burnt they are oxidized, meaning carbon dioxide and water is made.

The reaction that is involved in burning alcohols is exothermic because heat is given out. Form this reason the reactant energy is higher than that of the product.


The energy is given out when forming the bonds between the new water and carbon dioxide molecules. The amount of energy made by exothermic reactions like this can be worked out by using the formula Heat J = temp rise
°C X Mass water g X 4.2 J/g°C.  

The bonds that are made in an exothermic reaction can be two types. It could be ionic, where a metal is produced. Ionic bonding involves electrons transferring from one atom to the other consequently leaving an electrostatic force between them. The other form of bonding is covalent where atoms share electrons to complete their outer orbit. For example Methane, where four hydrogen atoms each share an electron with a carbon atom.


Apparatus

  • Stop clock
  • Thermometer
  • Boiling tubes
  • Measuring cylinder
  • Spirit burners containing the fuels
  • Balance
  • Matches
  • Clamp stand and boss head
  • Splints

Method

  • Gather all the apparatus as above
  • Set all the apparatus as shown below
  • Fill up a measuring cylinder with 20cm cubed of water and pour it into the test tube
  • Make sure the test tube is 12 cm off the surface below
  • Decide what fuel to test and how long should it be tested for. I have decided to test each fuel for 1 minute and 2minutes.
  • Weigh the fuel before burning starts, record the weight and record the temperature of the water.
  • Light the fuel and start the stop clock.
  • When 1 minute has passed I will take the flame off and measure the fuel and the temperature of the water in the test tube.
  • Repeat the test 3 times and then time the fuel burnt for 2 minutes.
  • Burn the other fuels as the method above states
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Variables

  • The weight of the fuels being burnt
  • The height of the test tube away from the flame
  • The time of burning
  • The amount of water in the test tube being heated
  • Type of beaker, glass
  • Same set of scales


The variable that has to be changed is…
· the type of alcohol used


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

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