Question 20N.3.sl.TZ0.c
| Date | November 2020 | Marks available | [Maximum mark: 4] | Reference code | 20N.3.sl.TZ0.c |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Outline | Question number | c | Adapted from | N/A |
Gasoline (petrol), biodiesel and ethanol are fuels.
[U.S. Department of Energy. https://afdc.energy.gov/]
Outline the advantages and disadvantages of using biodiesel instead of gasoline as fuel for a car. Exclude any discussion of cost.
[4]
Advantages: [2 max]
renewable ✔
uses up waste «such as used cooking oil» ✔
lower carbon footprint/carbon neutral ✔
higher flashpoint ✔
produces less /
OR
less polluting emissions ✔
has lubricating properties
OR
preserves/increases lifespan of engine ✔
increases the life of the catalytic converter ✔
eliminates dependence on foreign suppliers ✔
does not require pipelines/infrastructure «to produce» ✔
relatively less destruction of habitat compared to obtaining petrochemicals ✔
Accept “higher energy density” OR “biodegradable” for advantage.
Disadvantages: [2 max]
needs conversion/transesterification ✔
takes time to produce/grow plants ✔
takes up land
OR
deforestation ✔
fertilizers/pesticides/phosphates/nitrates «used in production of crops» have negative environmental effects ✔
biodiversity affected
OR
loss of habitats «due to energy crop plantations» ✔
cannot be used at low temperatures ✔
variable quality «in production» ✔
high viscosity/can clog/damage engines ✔
Accept “lower specific energy” as disadvantage.
Do not accept “lower octane number” as disadvantage”.
There were many good answers, but few candidates fully scored. Higher energy density and lower specific energy were quite common, and so references to damaging engines. Many students spent more time explaining each advantage rather than simply outlining. There were fewer journalistic and generic answers for this type of question than in the past.