Density - Experiment 2 Revision 2.1 Density Determinations...

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Experiment 2 Revision 2.1 Density Determinations To learn about intensive physical properties. To learn how to measure the density of substances. To learn how to characterize a substance using its density. To learn different methods for measuring volume. In this laboratory exercise, we will determine the densities of a Leaded Brass Alloy and a series of aqueous Table Sugar (C 12 H 22 O 11 ) solutions. The density of an aqueous Table Sugar solution of unknown composition will also be measured. This measurement can then be compared with the measured densities of the Table Sugar solutions of known composition to elucidate the Weight Percentage Table Sugar in the unknown sample. Substances can be categorized according to whether they are heterogeneous, a solution, compound or elemental. Regardless of the substance's nature, it can be characterized by its various physical properties; mass, volume, color, density, etc. Physical properties of substances are themselves sub-categorized according to whether they are intensive or extensive . Extensive physical properties depend on the amount of substance being considered, whereas intensive physical properties do not. Some examples are: Extensive Intensive Mass Density Volume Color Surface Area Melting Point Boiling Point Vapor Pressure Surface Tension Conductivity Intensive properties are particularly important because every pure substance has its own unique set of intensive properties which distinguish it from all other substances. And, even if the substance is not pure, its intensive physical properties can be useful in characterizing it. As an example, two metals which have a very similar appearance can be distinguished by considering their intensive physical properties: Cadmium Chromium color: silver white color: steel gray melting pt: 320.9 o C melting pt: 1890 o C boiling pt: 765 o C boiling pt: 2482 o C density: 8.642 g/cm 3 density: 7.20 g/cm 3 conductivity: 1.38x10 5 cm -1 Ω -1 conductivity: 7.74x10 4 cm -1 Ω -1
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A substance’s density is a particularly important intensive physical property of that substance. The density of a substance, or object, is defined as the ratio of its mass to volume: density = mass volume (Eq. 1) In effect, the density is a measure of the substance’s compactness. This property is important because it is extremely sensitive to the substance's environmental conditions and its composition. This is illustrated by looking at the variation in the density of Water with temperature and the variation in the density of Fuming Sulfuric Acid, Sulfuric Acid (H 2 SO 4 ) infused with Sulfur Trioxide (SO 3 ), with composition: Water Temperature [ o C] Density [g/mL] 0 0.99987 3.98 * 1.00000 10 0.99973 20 25 * 0.99823 0.99704 30 0.99567 40 0.99224 50 0.98807 60 0.98324 70 0.97781 80 0.97183 90 0.96534 100 0.95838 Fuming Sulfuric Acid % H 2 SO 4 Density [g/mL] 100 1.839 95 1.862 90 1.880 85 1.899 80 1.915 75 1.934 70 1.952 As can be noted from the above data, Water has a maximum density of 1.00000 g/mL at 3.98
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This note was uploaded on 11/06/2008 for the course CHEM 121 l taught by Professor Na during the Spring '08 term at John Brown.

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Density - Experiment 2 Revision 2.1 Density Determinations...

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