You could try plating a penny. Here’s a good writeup from Paul at ChemBark.
Puppy dissection.
I meant poppy dissection. Have the kids pull apart flowers. Had a class of 7 year olds enthralled with that for a good hour or so. Gave them sheets with the names and functions of the parts and then had them take apart the flower and try to identify each part.
Or you could go all the way and do poopy dissection. 
Oh, now that’s a good one… 10 year olds like the macabre, and pulling a tiny skellington from poop will go down brilliantly
Skeleton and pellets aren’t poop, before someone says something.
:smack: I did know that, once upon a time. Thanks for the reminder.
Still, fun times.
A fluorescent black light would be best, either a tube light that comes with its own fixture or a CFL.
You know, I never thought about what made it work. I just remember it being awesome 
Illustrate a runaway atomic reaction by building a big cage with wooden frame and chicken wire walls. Line the floor of the cage with mouse traps that have been set and have ping pong balls sitting on top. Then, set the whole thing off by tossing a ball into the cage. Mousetraps start going off and their balls start triggering multiple other mousetraps. Soon the whole thing is roaring and filled with flying balls, until the population of still-set mousetraps is depleted.
Lots of work, but a real crowd pleaser.
It’s really only good if they have a clear understanding of atomic theory, with is too much to ask of 10 year olds. So it just becomes a neat thing to do, but not science.
When doing solubility experiments with 10-11 year olds, I hate getting asked why some things dissolve in water and some don’t because there’s no really good kid friendly answer as far as I can tell. They lack anything other than rudimentary knowledge of atoms and molecules, and have no knowledge of dissociation and ions, so I end up telling them that some molecules can split into two in water and some can’t, but I hate it as an explanation but figure that their secondary school chemistry teacher can correct me when they get there.
My science teacher did it in the 1970s for a classroom of 12 year olds, though, and it wowed us…
From Straight Doper Bil Beaty, Kelvin’s Thunderstorm