Question

What are the primary sources of error in an experiment where you are calculating the caloric content of food by using a calorimeter that could explain any differences between you data and the label infomation for the number of Calories per gram? (Hint: How do these sources of error relate to the assumption that Qlost=Qgained?)

Answer 1

Following are some errors and their primary sources while performing the experiment of calculating calorific content of food using a caloriemeter.

1) Error in thermomete: The thermometer we are using may not have graduated properly.(Instrumental error).

2) Error in homogeneous stirring: If the water used is not stirred contineously and uniformly.(Humen error). Excessive and vigorous stirring may also add to the heat through increased kinetic energy.

3) Improper insulation of calorimeter : If calorimeter is not perfectly insulated ther may be heat transfer to the surroundings. Addition of cold water all of sudden when calorimeter is opened. This may cause haevy error in the measurment of heat transfered to the water- the water which is taken into consideration as acceptor of heat generated by oxidation of food (like fat, carbohydrate etc.)

4) Delay in reading the raised temperature of water. In this case the reading of temperature will be less than actually and this will give the calorific value of food less than expected.

5) Faulty measurment of water volume, O2 volume (oxidant of food), mass of food etc.

These are the errors and their primary sources.

Repeatation of the same experiment for 3 to 5 times and trying to minimize humen error by taking due care in noting down the reading also use og graduated instuments are some useful ways to minimize errors and get precies result.