Question 19M.3.HL.TZ1.b
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.3.HL.TZ1.b |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Suggest | Question number | b | Adapted from | N/A |
Water in a calorimeter is heated by burning food in oxygen. The temperature change of the water is used to calculate the energy value of the food. An experiment was set up to calculate the energy value of avocado.
[Source: © International Baccalaureate Organization 2019]
The energy value calculated for avocado was 750 kJ 100 g–1. The actual energy value of avocado is 840 kJ 100 g–1. Suggest a source of error in the experiment.
[1]
a. heat loss to the air ✔
b. heat transferred to the apparatus ✔
c. avocado may not be fully dried/incomplete combustion of avocado ✔
While most students were able to identify loss of heat as the primary source of error, some were distracted by aspects of the diagram and therefore wrote answers such as “incorrect amount of oxygen.” As in the case of the individual investigations, students often erroneously identify mistakes; for example, they regard a misreading of thermometers as a source of error.
