Gas behavior and how that affects our lungs

Welcome to your gas exchange lecture! You will pretend to be the teacher. 

Pretend your standards are to teach a class of 10th graders about gas exchange in the lungs. Now you may know quite a lot about the process, but they have never even considered why our body absorbs oxygen and releases carbon dioxide. Your job is to explain gas behavior and lead into how the body utilizes these behaviors. You will be asked a series of "why" questions, just as a teacher often has to answer. I will prepare some useful sites for you to find the answer while you are "looking it up, because that is such a great question, that you want to answer it to the best of your ability."