A student uses a bomb calorimeter to investigate the energy content of five different solid food samples (labeled A to E).
Inside the calorimeter, the food sample is ignited in an atmosphere of pure oxygen rather than normal air. Explain why this improves the accuracy of the energy content measurement.
Table 1 shows the carbohydrate content of each food sample in grams per 100 grams. Table 2 shows the measured energy content in joules per gram (J/g\text{J/g}J/g) across three trials.
Table 1: Carbohydrate content
| Food | Carbohydrate content (g per 100g) |
|---|---|
| A | 4.2 |
| B | 15.6 |
| C | 32.1 |
| D | 58.4 |
| E | 76.2 |
Table 2: Energy content (J/g\text{J/g}J/g)
| Food | Trial 1 | Trial 2 | Trial 3 | Calculated Mean |
|---|---|---|---|---|
| A | 650 | 690 | 640 | 660 |
| B | 2580 | 2420 | 2500 | 2500 |
| C | 5100 | 8900 | 5200 | 5150 |
| D | 9300 | 9100 | 9500 | 9300 |
| E | 12400 | 12100 | 12700 | 12400 |
Identify the anomalous reading in Table 2, stating the food sample and trial number. Explain how this anomaly should be treated when calculating the mean energy content.
Use the data to explain whether the results support the conclusion that foods with higher carbohydrate content have a greater energy content.
Name two other classes of large biological macromolecules in food, besides carbohydrates, that contain energy.
21 exam-style questions on Edexcel IGCSE Biology Biological molecules. Each one has a worked solution and a mark scheme showing where the marks go.