Determining Densities

Abstract:: Students will use two different methods to determine the densities of a variety of materials and objects. The first method involves direct measurement of the volumes of objects that have simple geometric shapes, while the second uses the water displacement method to determine the volumes of irregularly-shaped objects. After the densities are determined, students will create x-y scatter graphs of mass versus volume, and these graphs will reveal that objects with densities less than water (floaters) lie above the graph's diagonal, and those with densities greater than water (sinkers) lie below the diagonal.

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Floaters and Sinkers: Curricular Unit

Abstract:: This curricular unit introduces students to the important concept of density. The focus is on the more easily understood densities of solids, but students can also explore the densities of liquids and gases. Students devise methods to determine the densities of solid objects, including the method of water displacement to determine volumes of irregularly-shaped objects. By comparing densities of various solids to the density of water, and by considering the behavior of different solids when placed in water, students conclude that ordinarily, objects with densities greater than water will sink, while those with densities less than water will float. Students then explore the principle of buoyancy, and through further experimentation arrive at Archimedes' principle, which states that a floating object displaces a mass of water equal to its own mass. They may also be surprised to discover that a floating object displaces more water than a sinking object of the same volume.

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Abstract:: This lesson introduces students to the important concept of density. The focus is on the more easily understood densities of solids, but students can also explore the densities of liquids and gases. Students devise methods to determine the densities of solid objects, including the method of water displacement to determine volumes of irregularly-shaped objects. By comparing densities of various solids to the density of water, and by considering the behavior of different solids when placed in water, students conclude that ordinarily, objects with densities greater than water will sink, while those with densities less than water will float. Density is an important material property for engineers to understand.