Here's a fun, quick idea, for rainy day (or sunny day) fun, that not only teaches a quick science lesson, but also uses up some of those bread clips hanging around the kitchen.
Sadly, I can't remember the book, that inspired this boredom buster, but I did find a similar, but bigger, version at PBS-Kids' Zoom site.
Basically, all that is needed is a piece of plastic lid, cut into a boat type shape, with a bread clip glued to the back, a pan, or pool of water, and a drop of soap.
We originally tried making our boats out of card stock, but found that even a heavy covering of waxy crayon would not make them water proof.
But, the plastic boats work quite nicely. When you place one in a pan of water, it sits on top of the water, until you add a drop of soap, in the hole of the bread clip, breaking the surface tension of the water, and propelling the boat across the pan.
Once the surface tension has be broken, a fresh pan of water will be needed for each race. And, don't forget to wipe the soap off the bottom of the boat, or as soon as you put it into the water, it will take off, and zoom around. Of course, that's interesting, too.
It's great to be a homeschooler.