Option C: Energy - Energy density vs specific energy

[Elite X-Naut]

Hey everyone! As the title suggests, the syllabus says that we should be able to discuss "how the choice of fuel is influenced by its energy density or specific energy." I understand that a higher energy density and specific energy means it is an effective fuel, but how about when there's two fuels, one with a higher energy density and lower specific energy versus one with a lower energy density and higher specific energy? Which fuel would be the better choice?

I think I can save another post by asking my other question here: For everyone else doing Energy, we are aware that it is a new option and thus it has no practice questions from past exams. How are you guys studying/practicing for the upcoming paper 3? I have the Pearson textbook and the Oxford study guide, do you think that is sufficient? Thanks!

[Msj Chem]

It's mostly gases that have low energy densities (the value for hydrogen in my video is for compressed hydrogen). Liquid and solid fuels have higher energy densities. If you compare wood and natural gas for example, natural gas has a higher specific energy but lower energy density than wood. So which is the best fuel? Natural gas can be compressed to increase its energy density and it releases more energy per kg (higher specific energy). Therefore I'd say that natural gas is the better fuel if you only consider these two factors. 

 

The rest of my videos for option C can be found here:

http://www.msjchem.com/sl-option-c.html

[Elite X-Naut]

Thank you sir very much for your response. So we should generally stick to the fuel with a higher specific energy, and especially if it's a gas since they can be compressed, right?

[Msj Chem]

I would say that is correct. Of course there are other factors to consider such as price, carbon footprint, etc when evaluating fuels. 

[Elite X-Naut]

That is a good point. Thank you, and great job on the videos! They are very helpful and it's really appreciated.