In order to improve one's mead and recipe, it may be necessary to understand what is going on during fermentation, which requires some knowledge of chemistry. Many recipes have obvious flaws that can easily be detected. Of course chemistry is not almighty and experimentations are still necessary but understanding what is going on during fermentation enables one to discard some ideas and to avoid trying things which cannot work.
This chapter is for those who have never had a chemistry class or had one so long ago that they forgot it all.
It is not easy to teach in a few pages things which take years in high school. But one follows more willingly rules that one understands. And, as far as mead making is concerned, many rules are from chemistry. So having some basic knowledge in chemistry allows one to improve the quality of the mead without making (too many) choices at random.