We recently checked out the Kids' Guide to Building Cool Stuff from the library. It's got eleven fun projects that kids can do. When my four year old pages through it he says, "Can we do that?!" for almost every one. The projects are fairly easy to do and don't require anything too fancy, but mostly they are FUN! The results of most of the activities are impressive enough that it would hold the interest of an older child but not so complex that preschoolers can't make a significant contribution to them. This book would make a great gift for those boys that are hard to buy for. The only critisim I have is that they didn't really include the scientific explanation and when you've got a four year old always wanting to know why, that comes in pretty handy!
As a surprise I made my kiddos the Fizzle Rocks from the book. To say that they loved it would be an understatement. And the only things you need are baking soda, water, food coloring, and vinegar. And surprises to hide inside.
The kids really liked it, and then when they realized there were surprises in there they LOVED it.
We've also done the balloon rocket from the book:
If you liked this post, you might want to check out our cloud experiment too!