is it possible to convert oxygen to mechanical energy?

Answer 1

Sure. Allow it to react exothermically with pretty much anything that burns, use the resulting heat to boil water into steam, and use the steam to drive a motor or a generator.

Answer 2

It is being done on a huge scale on a second by second basis.
Probably, at this moment, the majority of the Internal Combustion Engines on Earth are converting the Oxygen of the atmosphere, combined with a fuel of some kind, into Mechanical Energy.
Oxygen itself doesn't burn but, it's needed for a combustion reaction to take place.
Many of the Mechanical Machines being run by the fuel/oxygen mixture, are themselves converting their Energy into other forms of Mechanical and Electrical Energy that is then converted to Heat and Light Energy...etc.
You could, in effect, say that the Oxygen IS being converted because, without it combustion can't occur.

Answer 3

food is the source of capability and milk and food grains could be used to make the engines to circulate. food grains could be used to offer alcohol which could be used to run an engine. Biofuels are consistent with this thought. The seeds have the oil that's used as biofuel.

Answer 4

Well if you compress it, you can use it to drive a piston, like in a pneumatic power tool, but you can do that with pretty much any type of gas.