A cell size and scale
We are using the Chemistry Program from Flexbooks CK-12 Curriculum. It is an online textbook (although they can be downloaded). It is a secular curriuculum, so you might want to beware for subjects like Biology. Brittany is enjoying it. It isn't boring or "hard on the eyes". There are also links to various science information and experiments throughout the chapters. I've been pretty impressed.
Here are a series of Youtube videos for Chemistry done by The Home Scientist.
Try Science Bob for some experiments or science fair project ideas.
We did a science experiment last week that worked fairly well and was VERY easy. (My kind of experiment.)
You need some of these........
Then you go into a very dark room and eat them. Try chewing with your mouth open and you should be able to see some faint sparks.
Go here to find out why. (FYI, I believe this will also work with pliers instead of teeth.)