Apart from the water temperature, state two other values to be measured at the start of the experiment.

1.

2.

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.

Avocados are known to be a good source of dietary fibre and contain all the essential amino acids. State one health benefit of a diet high in fibre.

Avocados are known to be a good source of dietary fibre and contain all the essential amino acids. Distinguish between essential and non-essential amino acids.

a. mass/volume of water ✔ 

b. mass of avocado ✔

a. heat loss to the air ✔

b. heat transferred to the apparatus ✔ 

c. avocado may not be fully dried/incomplete combustion of avocado ✔

helps in movement of food along alimentary canal/peristalsis/decreases transit time
OR
regulates bowel action
OR
prevents cancer/constipation/heart attack ✔

essential amino acids must be included in the diet and the body cannot make them «whereas the body can synthesize non-essential amino acids» ✔

Many students missed these relatively simple marks by using language that lacked precision using terms, such as “amount” rather than mass or volume. This is the same problem that affects students when writing their individual investigations submitted for internal assessment.

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.

This was answered well although many students resorted to colloquialisms when referring to bowel action.

Credit required two pieces of information about synthesis of amino acids and whether or not they were necessary components in a balanced diet. Hence few candidates gained credit as they only included one of these in their responses.