This video displays a very interesting experiment or magic trick involving the concepts of density and buoyancy. You will need an empty plastic bottle with its label removed, some water, and a ketchup packet. Using the concepts of pressure and density, this video demonstrates an interesting experiment which can also double as an interesting party trick; by squeezing a full water bottle, you can cause the ketchup packet to rise and sink in the bottle at your whim. This video is an interesting how-to for people who would like to learn some science as well as some "magic" for entertainment.
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