Dissolving Rocks

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. 

To make dissolving "rocks", start by making a dough from baking soda, water, and food coloring.  Start with one cup baking soda and a quarter cup of water and adjust from there.  I didn't even measure the second batch.  You want it moldable but not so wet that it won't hold its shape. 

Roll your dough around some surprises.  I used some small plastic frogs I picked up in the party favor section.  When I ran out of those, I started using coins.

Allow your rocks to dry overnight.

When the rocks are hard, fill a clear bowl with vinegar (we actually mixed ours with water) and drop them in!

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:

and the water bridge:

and making butter:

The vinegar launcher is next on our list!

If you liked this post, you might want to check out our cloud experiment too!