But you weren't thinking about chemistry back when you were roasting marshmallows.

Well, that's great for roasting marshmallows, but then when you get to high school chemistry and you're studying combustion reactions, all of a sudden you understand why oxygen is needed for fires.

For instance, when you're a kid and you're roasting marshmallows you kind of get the idea that you can get the fire going by blowing on it and you get the idea that you put a fire out by smothering it with water or sand.