Mad Science Camp: What can you do with bottles?

If you are doing The Joy of Toys Camp, you probably are saving bottles.  What other science projects can you do with bottles?  Make a Soda Bottle Bird Feeder.  Make Ecosystems in 2-L bottles.  The systems look like this.  Let your kids use plastic bottles to flip bottles. (Here is a scientific explanation for bottle flipping.). You know how to crush Crush Cans?  You can Crush Plastic Bottles, too.  Here is Drip Drop Bottle—save all kinds of bottles.  Do you have hundreds of bottles?  Make a Plastic Bottle Greenhouse.  The issues with a plastic bottle greenhouse are bottle collection and storage.  Wash out the bottles before storing!!! Ask me how I know.   My kids have built plastic bottle greenhouses twice.  Yes, you need hundreds of bottles—the same size.