Prescribed practical B2 - Investigate the energy content of food
A simple investigation can be conducted to investigate the energy content of a food sample.
Procedure
- Add water - around 20cm3 - to a boiling tube clamped in a retort stand.
- Record the starting temperature of the water.
- Place food sample on mounted needle.
- Ignite the food sample using a Bunsen burner.
- Hold the burning food sample under the boiling tube of water until completely burned 鈥 it may be necessary to relight the food sample.
- Record the final temperature of the water.
- Record results in a table.
- Calculate the change in temperature caused by the burning food sample.
- Repeat steps 1- 8 with this food type to increase reliability.
- Calculate the average change in temperature for this food type.
- Calculate the energy released by this food type using this equation: Energy released (J) = mass of water (g) x rise in temperature (掳C) x 4.2
- Repeat steps 1-8 with different food types for comparison.
Results
A large increase in temperature indicates the food contains a lot of energy.
The results obtained from this experiment are usually lower than the actual energy content of the food because during the experiment, the entire food sample may not be burned, some energy is lost to the air and some is used to heat the glass of the boiling tube.
Controlled variables
- Mass of food
- Mass of water
- Distance of food from water