No, I just typo'd it. Anyway, just look it up. Nitrous is mixed with fuel. There are different types of systems, sure, but it HAS to be mixed with fuel to become volatile. When they inject n02 in a car, it either mixes with fuel at a nozzle connected to the intake manifold from the fuel and nitrous solenoids "wet system" , or nitrous is injected "dry" by itself, but mixes with fuel from the fuel injectors inside the engine (with more fuel added from supplemental fuel system).
Nitrous oxide REPLACES normal air because nitrous is almost like a perfect atmosphere for the engine to breath. Think of when it was used first. In ww2, they used "war time power" to give the planes more hp because of the lack of air at those elevations.
Its not that cool air mixes better with fuel or whatever, its that cooler air is denser, thus more is pulled on the intake stroke. Also, when it is heated to 520 f, it breaks down and releases more oxygen. More oxygen= more fuel (proper a/f mixture ) = more power. The presence of more oxygen lets the fuel burn more rapidly. The more fuel it burns in the same amount of time results in higher cylinder compression. That is the main source of the power. Just like if you raised compression on your engine, it would also gain horsepower.
As compressed nitrous oxide is injected into the manifold, and boils creating temperatures of - 127 f. That cools the air that isn't introduced by the nitrous oxide itself, allowing more of it to enter the combustion chamber. You could call n02 "super air" for cars.