Fair testing
When comparing different foods, it is important to carry out a fair test.
Several variables should be kept constant:
- the volume of water
- the mass of food
- the distance of the flame from the boiling tube
There are a few sources of error in calorimetry:
- it is difficult to maintain a constant distance between the burning food and the tube, varying the heat loss to the environment
- it is difficult to minimise heat loss when transferring the burning food from the flame to the tube
- in this method it is possible that incomplete burning of the crisp gives an inaccurate measurement of the mass burned
An improvement could be to use a bomb calorimeter:
- sample is burned in a sealed chamber to reduce heat loss to the environment
- sample chamber is surrounded by another chamber of water in which the temperature change is measured
- sample is burned in pure oxygen to ensure complete combustion