Practical: Energy Content in Food (Edexcel GCSE Biology)

We can investigate the energy content of food in a simple calorimetry experiment

Apparatus

• Boiling tube
• Boiling tube holder
• Bunsen burner
• Mounted needle
• Measuring cylinder
• Balance/scales
• Thermometer
• Water
• Food samples

Method

• Use the measuring cylinder to measure out 25 cm³ of water and pour it into the boiling tube
• Record the starting temperature of the water using the thermometer
• Record the mass of the food sample
• Set fire to the sample of food using the bunsen burner and hold the sample 2 cm from the boiling tube until it has completely burned
• Record the final temperature of the water
• Repeat the process with different food samples
  • E.g. popcorn, nuts, crisps

Investigating the energy content of food samples diagram

Different food samples can be burned in a simple calorimetry experiment to compare the energy contents of the samples

Results

• The larger the increase in water temperature, the more energy is stored in the sample
• We can calculate the energy in each food sample using the following equation:

• • 4.2 kJ is the specific heat capacity of water, meaning that it is the energy required to raise 1 kg of water by 1 °C
  • 1 cm³ of water has a mass of 1 g

The energy content of food samples table

Limitations

• Incomplete burning of the food sample
  • Solution: Relight the food sample until it no longer lights up
• Heat energy is lost to the surroundings
  • Solution: Whilst heat lost means that the energy calculation is not very accurate, so long as the procedure is carried out in exactly the same way each time (with the same distance between food sample and boiling tube), we can still compare the results

Applying CORMS evaluation to practical work

• When writing about practical investigations the CORMS evaluation can be used:

CORMS provides a framework for writing about practical investigations

• In this investigation CORMS can be applied as follows:
  • Change
    • We are changing the type of food in the sample
  • Organisms
    • This is not relevant to this investigation as we aren't using an organism
  • Repeat 
    • We will repeat the investigation several times for each food sample
  • Measurement 1 
    • We will measure the change in temperature of the water
  • Measurement 2 
    • The mass of the food will be measured after the food sample has burned out
  • Same
    • We will control the volume of water used and the distance between the food sample and the boiling tube during burning
    • The food will also be relit every time it goes out until it no longer relights