Well, there is a way you can think of a good question around these points. Something like, Ideal gasses can't be liquified, but other gasses can. Why is that? You'd frame the answer with examples of how real gasses are not ideal gasses. Or maybe you could ask, ideal gasses can't be liquefied, noble gasses can only be liquefied at very low temperatures and very high pressures, other gasses are liquefied at more moderate conditions. How are these differences explained?