My teachers rarely ever set homework for science. I think they knew that notes are important, and there usually isn't that much homework they can possibly set you.
That being said, when they did set homework it was always with good reason. Occasionally, it was just cause the teacher was too slow, which is also potentially impacted on by an unsettled period 6 class or something. But usually, in the instance that they actually bothered to set homework it was because the concepts taught were more difficult to understand. More skills in the science courses actually had to be used for this question, than just memorisation.
If your teacher is setting you homework on random questions and not checking them, then provided you include (or incorporate) what would've been homework into your notes then that's probably fair enough. But if a teacher either gives you a hand-in question that they'll mark, or they give you questions on largely skill-based concepts, then I'd say do them.
Final decision is your own though. And never forget time management; it's always hard, but you need to juggle between what you have to do. Especially stuff like assessment tasks.