HOW to make a container float then sink then float back up?

Question

How tocreate a container that when you put it on water it will float for a while then it will start sinking and finally it will float back up?HOW?

Answer 1

you just described a sub.

you never said how big this "container" could be......

Answer 2

here is one in a sealed environment

http://www.sciencebob.com/experiments/ca...

and here is a video that explains the properties pretty well.

http://www.videojug.com/film/how-to-make...

And here is the old baking soda powered subs

http://www.starmagic.com/3D3A2D02.html

The soda will start to dissolve in the water as it sinks, it will react with the water and release carbon dioxide, which will build up and float the sub back to the top. When it gets to the surface it will "burp" out the gas and start to sink again.