When we have multiple options of energy to choose from, how do we know which energy contains more energy than the other energy? Some ways we can use are specific energy and energy density.
So what is the difference between specific energy and energy density? Specific energy is the number of joules that can be released by each kilogram of the fuel. Meanwhile, energy density is the number of joules that can be released from 1m^3 of a fuel. Hence the main difference would be while specific energy deals with the amount of energy per mass, energy density deals with the amount of energy per volume.
Table above shows specific energy and energy density of some common fuels we use in the world today except for nuclear fusion which can be a great energy source if we somehow find a way to operate it with affordable cost.
Q1's Guide To Unit 8 of IB Physics! 