My wife homeschools our children, and she does the teaching. Sometimes she waits for Saturday morning to do the science experiments, so I can participate. And sometimes, because of a kids book they've read, or an idea I've had, I get to teach them some mathematical or scientific principal, or I come up with an experiment or demonstration (depending on the complexity or danger levels – sometimes, I get a bit too mythbustery for them to safely help).
The kids were reading a book which mentioned photosynthesis, and they asked how it works. I gave them the quick "the plant turns sunlight, water, CO2 into sugar, which it uses for engery." That wasn't enough for them. SO I went to the chalkboard and did a quick stoichiometry; then I got out some handy Duplo® bricks, made some water and CO2 molecules, which I put on a Duplo® base, to act as the leaf. Our hands became the sunlight, and we … disassociated … those molecules. :-) Then I rebuilt them into sugar* molecules that went deeper into the plant, and O2 molecules back into the air. They seemed to like that explanation.
*Okay, in all honesty, my first attempt produced methane. I just went for the easiest hydrocarbon, and didn't think about what it was until later. Oops, sorry plant. :-) I added a few more molecules and got something a bit more sugary, but I cannot remember now which simple sugar I produced (probably still not one from most plants, but not as unlikely as methane).
"Do you want to play a game on the chalkboard?" I asked this question after we'd read The Boy Who Loved Math for the umpteenth time, and I thought they might enjoy seeing how the sieve, which was featured in an illustration in the book, was made. I doubt much stuck, but they seemed to enjoy taking turns crossing out numbers. :-)
(I'll admit, this one was more for me. Especially after I got the kids excited about a boom, and there never was one.)
I like hydrogen. And I thought it might be interesting to separate some out from water, with the hope that I could fill two balloons (one with oxygen, one with hydrogen), and later ignite them to see which gave the more interesting burn (the potential boom). After some failed setups, I decided against separate collection; besides, putting the H2 and O2 in the same container would provide a ready source of oxygen for the combustion.
My setup: a 1L bottle filled with a saturated baking-soda-in-water solution (using table salt as the electrolyte, I was reminded in my research, has the potential for chlorine gas; not a good idea). I punched two holes near the top of the bottle, and stuck in a couple of wooden pencils with graphite exposed on both ends; I used hot glue to seal the holes. Connecting two 9V batteries in series to the graphite leads, I was able to get the tell-tale bubbles of electrolysis: success. I placed an inverted balloon in the end of the bottle, and waited; it never did inflate.
Presumably, too much was leaking out through the imperfect seals. I should probably switch to a couple test-tube-equivalents filled with water and inverted in a bucket over the graphite electrodes; that's the way most of the youtube videos I found did it. But to get some "boom", I tried removing the balloon, and bringing a lighter right to the top of the bottle, where the gas was bubbling out; I got a couple of tiny "pops", but nothing that excited the kids. Sorry.
What I'm calling variants of sudoku, whether simplificiation of or extrapolation from the original.
My daughter enjoys playing the "number game" on my phone with me; I tell her where to put the next solved number ("put a 2 between the 5 and the 6 in that grey box", etc.). I've thus started doing simpler grids on the chalkboard — with just a 4x4 grid, and one number missing from each row or column, and haven't made the logic require one-of-each-per-2x2. The other day, she asked for "1-5" instead of "1-4": since I haven't introduced her to the boxes, the fact that 5x5 cannot have the sub-boxes is irrelevant.
But the 4x4 got me thinking: just how many valid solutions of 4x4 are there? 288 (that's just two gross). If you care about the details, see my highly mathematical PseuDoKu article.
Otherwise, reload the page to see a different board.
For playable kids' sudoku, see 1sudoku.net's 4x4 and 6x6. If you'd rather avoid the ads on 1sudoku.net, try out sudoku-download.net, which has PDF's of 4x4 thru 25x25 (and even example 49x49 and 64x64
