[lwl]

My chemistry examination is approaching and our teacher has given some hints to us. She said that one of our questions will be about "Comparison of similar gases".

However, I have read my books and I have also searched this on the internet. I cannot find much information about it. So, can any of you guess what are the similar gases?

I have thought about it, do you think that the teacher will ask us to compare nitrogen dioxide and bromine? Since they are also common brown gas. Moreover, can you think of some gases which are common and easy to compare?

This is my final exam in my secondary school. I afraid that I will fail on my chemistry examinations
So, I really hope that all of us can help me. Thank you 

[Arkcon]

Instead of searching for different gasses, I'd instead review the formulas for the gas laws that you've learned or can find in your text book.  And see if there are examples of gas comparisons.  The color, of two gasses, ... no, I don't see that as a final exam question.