Investigating the Energy Content of Foods (WJEC GCSE Biology)

Specified Practical: Investigating the Energy Content of Foods

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

• This involved burning a sample of food under a known volume of water

• The energy from the food is transferred into the heat of the flames, which in turn is transferred into the heat of the water

• The change in temperature of the water sample reflects the quantity of energy in the sample and can be calculated mathematically

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 25cm³ of water and pour it into the boiling tube

• Record the starting temperature of the water using the thermometer

• Weigh the initial mass of the food sample

• Set fire to the sample of food using the Bunsen burner and hold the sample 2cm 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 the food sample and boiling tube), we can still compare the results

Risk assessment

• A hazard in an experiment is something that could potentially harm you

• A risk is the harm that could occur as a result of the risk

• A control measure is the action taken to reduce the chance of the hazard causing a problem

Risk assessment of calorimetry practical table