Practical: Energy Content of a Food Sample (Edexcel IGCSE Biology)
Revision Note
Practical: Energy Content of a Food Sample
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
Food sample | Mass of water / g | Mass of food / g | Initial water temperature / °C | Final water temperature / °C | Change in water temperature / °C | Energy transferred per gram of food (J) |
---|---|---|---|---|---|---|
Popcorn | 25 | 8.5 | 20.5 | 31.2 | 10.7 | 132.2 |
Walnut | 25 | 8.1 | 20.4 | 34.1 | 13.7 | 177.6 |
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
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