Water benders can manipulate trees and plants..but I'm not sure about earth benders beeing able to manipulate Iron and steel

Earth benders can manipulate, Coal and Sand, and probably raw iron. The fire nation smelts the Iron down to make their tanks and weapons, so the earth nation can't utilize their offense.

Hmm, but if someone uses a sword or spear that is not a member of the Fire Nation then could an Earthbender manipulate the sword or spear? Oh, so an Earthbender can't use trees and plants and things like that?

No, It's still been manipulated by man, I'm talking pure iron ore, or maybe they can't control it at all. In the episode the swamp, Waterbenders manipulated the water in the plants, so thats a waterbending thing.

What if the wood was petrified, I wonder?

But I think Kaji means iron that hasn't been mined or modified or anything.

Yup, any kind of tempered weapon would be out of a earbenders ability to control. I assume that goes for glass ( super heated sand) and any other metal thats had its natural impurties removed. Also I doubt they could bend the minerals found in ocean water... (Unfair considering waterbenders can control the water in plants and animals)

Considering the potential for Waterbending, I would say it is the most powerful element. On any opponent, just freeze the water in their bodies and they will die. Or throw water on them and freeze it and crush them. If a Firebender uses a fire attack, drop the tempurate, raise the humidity, and bring the water from the air together and block the attack then use the steam made from that in your next attack. If an Earthbender attacks with rock, just do the same thing but freeze the water around the rock and send it right back at them. You would have to be an Advanced Waterbender to do this though. Actually...no, now that I think about it thats not fair unless Earthbenders could be able to use the minerals in someone elses body. The human body is composed of plenty of minerals. Hmm, this is starting to seem unfair...

Yeah it does suck but water isn't a real offensive bending discipline so that is why is it really adaptive. Earthbending can be used to block many attacks but water would be a poor barrier so I think that is why waterbending has such a wide array of things to do. I think sand would be pretty hard to bend because so many different things are in sand.

Water can be used as a fairly strong defense: Ice. Thick Ice. Although, it isn't as hard as rock, and can be melted much faster than rock. I'm not sure...and when you bend something, do you have to focus on only one thing, like pure granite, or can you just focus on a chunk of ground? Water benders bend water, which has other things in it, so when they bend, does it purify the water because they cant bend the other things in it? I don't know....this is really scientific. Or maybe we are just making it harder than it should be...

Yeah I usually thought that earthbending would be hard because earth contains so many different things. But we might just be going to deep into it, but still why I don't get is how in the episode in Zuko Alone the earthbender launched some earth at Zuko and Zuko just tore through it with his rocks. I still have a hard time following the show in some cases. Thanks a lot science.

cartoons are not really meant to be realistic, plus Zuko was stronger then the earth bender (well he did need bending )

I've said before, and I'll say it again. Freezing blood is completly out of the question for waterbenders, we can't assume techniques that we haven't seen. Plus even if it was possible, there are so many things that can counter the freezing. (Firebenders abnormal body heat) or something like that. waterbenders also can't control humidity, thats a combination of air and water, So don't assume things that we haven't seen on the show. Imagine if i mentioned lightning bending before we saw it on the show, people would go crazy.

That's true. I guess we will have to stick to what we've been given