DS got this for his birthday.
https://www.amazon.com/Learning-Resources-LER2784-Primary-Science/dp/B0035EQDTU
He just spent close to two hours mixing water/colors in the test tubes and beakers. Now I know we could do that without a science kit but there are some other experiments we are looking forward to doing too. We are just getting started and he is so excited about it!
Re: toy rave (preschool)
DS got this one and did it with my Mom several times:
https://cherryhill.learningexpresstoys.com/buy/sxp509/fizzy-foamy-science-kit-by-scientific-explorer/
And sure we could do it without the kit but I like that it is all inclusive and you toss it when you are done instead of having chemicals all over the house for experiments - and honestly I would just never do it without the kit even though I should.