In Avatar: The Last Airbender and The Legend of Korra, we see element bending, which is divided in four (water, earth, fire, air). It's easy to understand how it works: if one has a bending ability, they can control the element without touching it. However, as the series progresses and we see technological advances, things start to get complicated.
What causes me more confusion is earth: it's shown that metal bending is possible, but only because metal still has some earth impurities in it. But, earth is not an element; it's a composition of both mineral and organic materials. Also, we see lava bending (which is just hot earth), and the bending of some liquid metal-like poison (is it mercury?)
So, what on Earth are they bending? (pun intended, sorry)
What I can understand is:
- Water is H2O (we never see oil bending, do we?)
- Air is O2 (maybe?)
- Fire is... not even an element, is it? It's just combustion, which as far as I know also needs oxygen
- Earth, I imagine it has something to do with carbon, but then how do we explain the liquid metal?
It's interesting that we see the Avatar world develop technologically (so also scientifically, I assume), so that ultimately the bending abilities may have a scientific explanation.
Is there anything in canon that explains the exact elements or compounds they are manipulating?