Two complementary descriptions

Theoretical and physical ideas

It is important to recognise from the very outset that this description of the action of fuels, in terms of energy and energy stores, is theoretical or abstract in nature. It doesn't belong to discussion in the everyday, or lived-in world. You can't look down a very powerful microscope to find the chemical store inside the petrol! We think it is helpful to make a clear distinction between the everyday description and the energy description.

These are linked, but different:

Both the energy and the energy store are theoretical ideas, whilst the petrol belongs to the everyday world. It is the energy store idea that allows us to describe and make calculations about the burning of petrol in a car engine, but it is the petrol that you must carry along in a can if you run out of fuel!

You probably won't find yourself having conversations about stores of energy at the pump. But nevertheless the energy in these same stores have a very real and physical effect on what's possible (and what isn't).