It's really difficult to make the iodine clock reaction work when you have no balances and therefore no idea what the molarity of your solutions really are. Magnets, on the other hand, work perfectly well without balances. Nik found some magnets and a little packet of iron filings before he left on Sunday, so we're going to do magnetism for the 8th and 9th graders since it's in their curriculum (though all the pictures here are of 8th).
The kids have divided into their groups, and I give each a little box with some iron filings spread out. After a little introduction to magnets (with the help of a compass), I hand each group a bar magnet, and have them play with getting a field pattern in the filings.
When I go around and tap the box as it rests atop the magnet, the filings fall into place and the kids eyes widen. "Look, it's making a pattern!"
Now to explain the why, and how the field goes from north to south in all directions and how we can find what the field looks like by looking at the pattern in the filings.
And now a little induced magnetism to end the lesson. Iron piece = not magnetic. Iron piece + magnet = magnetic. Take off the magnet, and the filings fall off the iron piece again. It's like mag(net)ic!