I only have two 'light' examples. So you definitely learn something, but it's more fun than anything else. They're not on gog though so you'll have to set up each through dosbox.
Quarky & Quaysoo's Turbo Science - It's more of a general science educational game more or less starting at the senior level of primary school. It covers a bit of chemistry and electricity. But it's an incredibly cool game in its own right.
LGR did a video on it.
Island of Dr Brain - A much bigger game than Turbo Science from the same time that also covers a wider range of subjects : mechanics, music, language, art, math. As for chemistry, biology, electronics and genetics : apart from biology, there is a puzzle related to each. And each puzzle has I think 3 versions, depending on difficulty. The electronics puzzle comes in the form of a logic gate puzzle, and it's most difficult version is a real head scratcher!
For all of the subjects tested in the game's puzzles, a light treatment is given in the game manual which is almost like a small textbook that's fun to read. The manual can still be downloaded. Check it out:
http://www.sierrahelp.com/Documents/Misc/The_Island_of_Dr_Brain_-_EncycloAlmanacTionaryOgraphy.pdf It's completely readable, but for some reason not very high quality. I've searched before but couldn't find a high quality version online.
Btw. I often hear that its precursor Castle of Dr Brain is the better game of the two.