Chemistry play idea for preschoolers [View all]

[Victor_c3]

I'm not sure if this is too far off topic for this forum, but I'll post it anyways (and take a beating if I deserve it).

I have two daughters aged 2 and 4. I work as a chemist (although I'll admit I'm not a very good one) and yesterday my kids got their hands on some baking soda and vinegar and were having a blast just mixing it together. I've been trying to think all day of other things I could add to the mix to make it more interesting and fun for them. The idea is I'll set up a bunch of solutions outside where I don't have to worry about a mess and just let them play around and pretend to be a scientist (or a chemist) like their dad. They pull a pipette full of a solution from a beaker and add it to a test tube to see what happens.

So far for my chemicals I have:

dilute soap solution (when mixed with baking soda and vinegar it'll (hopefully) make a really massive foam mess)
beakers of colored water
baking soda
vinegar

I "borrowed" some disposable plastic supplies from work:

pipettes
50ml test tubes
10ml test tubes
100ml beakers
PH papers

Does anyone have any ideas of chemicals or labware that I could add to their little chemistry kit that I'm putting together? I don't want anything that would be toxic by any means and I'm trying to keep the equipment to things that don't break and don't cost a lot of money.

Thanks for any ideas!