Back to the full dot-point answer
VICChemistryQuick questions
Unit 3: How can design and innovation help to optimise chemical processes?
Quick questions on Fuels, energy content and energy density: VCE Chemistry Unit 3
7short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is fossil fuels vs biofuels?Show answer
Fossil fuels release CO2 that was locked underground for millions of years, adding net carbon to the atmosphere. Biofuels release CO2 that the source crop absorbed during growth in the same season, so the net carbon contribution is close to zero (ignoring transport and processing emissions). This is the "carbon neutral" argument for biofuels.
What is energy content vs energy density?Show answer
Two different quantities, both used to compare fuels.
What is comparing fuels?Show answer
The "best" fuel depends on the application.
What is confusing energy content with energy density?Show answer
"kJ per gram" and "kJ per litre" are different. A high-energy-density fuel may have a low energy content (e.g. diesel is denser than petrol so it wins on per-litre but is similar per gram).
What is calling biofuels "zero carbon"?Show answer
They are close to carbon neutral in the combustion-vs-photosynthesis balance, but the processing, fertilising and transport stages still emit CO2.
What is saying coal is the highest-energy fuel?Show answer
Coal is dense and cheap, but per gram it releases less energy than petrol or methane because it has fewer C-H bonds (more C and impurities).
What is forgetting hydrogen's storage problem?Show answer
Hydrogen has the highest kJ g^-1 but the lowest kJ L^-1 as a gas. Markers reward the explicit storage-volume point.
Have a question we have not covered?
This dot-point answer is short enough that we have not extracted many short questions yet. Read the full dot-point answer or ask Mo, our study assistant, in the chat for follow ups.