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Reprinted by permission of Dick Berg, University of Maryland, for use on this website.

The demonstrations contained and referenced herein are listed for the purposes of cataloging and describing physics demonstrations which should be conducted only under the direction of a trained instructional support professional or physicist. These demonstrations are not presented for the purpose of being conducted by persons unconnected to this Facility and/or persons not consulting with or being supervised by the recognized instructional support professional or physicist and his/her staff. The University is responsible only for those demonstrations carried out using its own equipment using established safety and scheduling policies, and bears no responsibility for those choosing to use this source material for their own purposes. All demonstrations described and contained herein are public domain, and can also be found in reference materials in libraries, bookstores, and electronic sources.

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The mangle wood, the iron wood and the lignum vitae are some of the few woods that are dense enough to sink in water.

The pumice rocks have a density which allows them to float in water much like an iceberg. 

The two silver balls both have the same mass, but the densities are vastly different.  One has a diameter of 2.86 cm and will sink in water, and the other has a diameter of 12.7 cm and will float very nicely.