Well, I'm assuming you don't want the boring ol' "it's a video-game" answer, so here's my opinion. The tip of the fuse on each bomb has a special substance on it much like that on the head of a match. The inside of the bomb-bag, right near the opening in the top, is very rough, and so when Link pulls out a bomb, the tip of the fuse strikes the rough part of the bag, and viola, we have fire.
Of course, that also raises the question of how he pulls the bombs out of his bag so fast, and without the aforementioned bag anywhere in sight. But then, that wasn't the question
My answer is that the bombs are 'magic' and the fuse ignites on contact with air.
That would also involve a chemical reaction....and no, Matches do not need a chemical reaction to ignite by striking them quickly along a rough surface, Just enough friction to cause the substance to heat up and set fire.
That's what magic was meant to mean. Also matches do need a chemical reaction to ignite. It needs two chemicals and friction to cause heat and thus you have a very small torch. Just try looking up the science of matches and you'll find it to be true. But not on wikipedia. It's a terrible site.
Magic and Chemical Reactions are two very different things.
of course science is acceptable in zelda ex barnes the bomb maker, the observatory guy and the the lake hylia laboratory. there are others im sure.
True there were some that studied science. No question/argument there. But it generally wasn't accepted. Also did you see Barnes say somewhere or imply something that bomb-making was science? Nope. The Lakeside Laboratory was indeed science but the scientist that ran the place was obviously insane but knew what he was doing. And also I don't know who the observatory guy was so I can't accuratly answer that.
It doesn't make a difference if it generally wasn't accepted during those times, People still did it. No matter what they called it is still science, If I got several people to call a Poodle a Greyhound would it therefore be a Greyhound? I think not....
The Observatory guy was an old Astronomer of sorts, He had a large telescope in which you could look at objects in space with. That is science also.