Chemistry Questions HELP?

I am looking at other sources for information, but I need the information today because I have to do something with it by the end of the day.

In the end I need a paragraph for each question (there are 2) so please explain in depth but in a way that someone who is not very good at chemistry can understand.

Background info: Put water in an empty aluminumn can and than boil the water in the can ( when the water is boiling heat is also applied to the can). After the water boils put the can in cold water (about as cold as the maxiumn temperature of cold tap water from a faucet), and the can implodes and is squished. At this point the can did not break and looks no different than a regular aluminumn can except for the fact that it is squished.

Question which is the result of the lab in the background theory above: Explain why did the can implode.

Question #2

Background info: A large empty plastic soda can (costco size) is filled as much as possible with water. A dropper ( not sure what it is called but its basically a light weight plastic device which is usually used to obtain very small amounts ( a few droplets or less) of a substance is put into this large soda can with the dropper being almost filled up to its maximun capability that it can hold. The dropper is supposed to represent a diver in a body of water( maybe an ocean). The bottle with the dropper in it is than going to be squeezed. While this pressure is being exerted onto the bottle the dropper which is supposed to be representing a diver sinks down to the bottom of the bottle. When the bottle is not being squeezed the dropper stay toward the top of the inside of the plastic bottle.

Question which is the result of the background information about the very large soda bottle : Why does the dropper sink.