Question 20N.3.sl.TZ0.9e
| Date | November 2020 | Marks available | [Maximum mark: 2] | Reference code | 20N.3.sl.TZ0.9e |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Compare and contrast | Question number | e | Adapted from | N/A |
Gasoline (petrol), biodiesel and ethanol are fuels.
[U.S. Department of Energy. https://afdc.energy.gov/]
Contrast the molecular structures of biodiesel and the vegetable oil from which it is formed.
[2]
Any two:
biodiesel has smaller molecules/single «hydrocarbon» chain AND oil has larger molecules/multiple «hydrocarbon» chains ✔
biodiesel is methyl/ethyl ester AND oil has «backbone of» glycerol joined to fatty acids ✔
biodiesel contains one ester group AND oil contains three ester groups ✔
Do not accept properties such as “less viscous” or “lower ignition point”.
Quite disappointing with few candidates producing answers that showed deep understanding. Answers such as less viscous or lower ignition point were common. This question specifically asks for contrasts in the structures not the properties of the compounds. Students need to be reminded that a contrast statement requires something about each substance.
