[tlhIngan Hol] {yInSIp} and {voQSiP} (oxygen and nitrogen)

I have learned that {yInSIp} is "oxygen" and {voQSIp} is "nitrogen." Naturally, I looked up {SIp} and found that it means "gas." It would seem, then, that these words refer to the elements in their gaseous states. Today, though, Duolingo gave me {voQSIp taD} as "frozen nitrogen." I believe that frozen nitrogen is nitrogen in its solid state. That would make {-SIp} superfluous, and I would expect it to be {voQ taD}. Do elements that have a gaseous state retain {-SIp} regardless of the element's state? Would it always be something like "frozen oxygen gas" and "frozen nitogen gas"? Sent from Qo'noS