Energy Density of a Fuel (WJEC GCSE Chemistry: Combined Science)

• We can experimentally determine the amount of energy released by a fuel 
• We do this using calorimetry
• The apparatus for this experiment is shown below  

Diagram to show the set up of calorimetry equipment

A lid is used to prevent heat loss

• The steps are: 
  1. Measure a fixed volume of water into a copper can
  2. Weigh the spirit burner containing  a fuel using a balance
  3. Measure the initial temperature of the water
  4. Burn the fuel and stir the water 
  5. Wait until the temperature has risen by approximately 20 ^oC and extinguish the flame
  6. Record the final temperature of the water and re-weigh the spirit burner

• To calculate the energy released by the fuel we can use the data obtained from the experiment above and the specific heat capacity of water 
• The specific heat capacity, c, is the energy needed to raise the temperature of 1 g of a substance by 1 °C
  • The specific heat capacity of water is 4.18 J/g/°C
• The heat energy change is calculated using:

Q = m x c x ΔT

• • Q = the heat energy change, J
  • m = the mass of the substance being heated, g
  • c = the specific heat capacity, J/g/°C
  • ΔT = the temperature change, °C