Science demo ideas?

Oh, and as long as I'm on here, does anyone have ideas for science demos that are appropriate for kindergarden kids? Bossman's recruited me to do science demos at his son's school with the other first year in the lab (who, fairly enough, is not enthused about this extra work).

My current ideas: lemon as a battery, color changing "clock", glow in the dark slime, "elephant toothpaste", and colored smoke (if we can do it outside/we can scrounge up the materials).

Bossman is insistent on doing thermite. Which is super cool (hell, I absolutely still love that demo), but I am convinced we have the potential for half of our audience crying. I am secretly hoping that the department won't let him check out the stuff.

Therefore, we'll probably be doing thermite, but that leaves room for one or two more demos. Bossman has grudgingly approved lemon as a battery.

Any other ideas would be much appreciated.