Whalley, E. Dymond, J. Padua, A. Saville, G. Brielles, J. Login: Guest. View in A-Z Index. Measurements in Liquids. Measurements in Gases. Malbrunot, P. References Wood, R. Related content in other products Begell House Inc.
Repeat the measurements at least twice to obtain additional values to calculate an average density. The results are shown in this table. The average measured density was 0. To determine the density of an irregular solid in pellet form, add approximately 40 mL of water to a clean and dry mL graduated cylinder.
Record the exact volume. Place the cylinder on an analytical balance and tare. Add approximately 10 pellets, and record the new volume after the addition. Weigh the cylinder, water, and pellets.
The mass is only the pellets, as the rest have been tared. Make at least two additional sets of mass and volume measurements to calculate an average value of the density. The density for zinc was measured for three different samples. It was found to be 6. Note that, since the measurements were made in a graduated cylinder, which is less precise than a volumetric flask, the density has lower degree of precision.
Let's now look at several different applications of density to different field of scientific research. Density is useful for identifying or validating pure materials, such as elements or other species of known purity.
For example, because gold has a higher density than many other cheaper metals, calculating the density of a gold coin is a quick and inexpensive way to test for its purity. If the density does not match that of gold, the coin is not pure. Here, a gold coin was found to have a mass of Density measurements can also be used to identify an unknown substance if a list of possible reference densities is available, and can be used to distinguish between metals similar in appearance.
In this example, the scientist is trying to identify two samples of shiny silver metal, which could be either aluminum or zinc. While the two samples have the same mass, their volumes are considerably different. The densities were determined to be 2. Finally, differences in density are useful for separating components of a complex mixture. In a method called density gradient centrifugation, decreasing concentrations of sucrose or polymers are layered to create a gradient.
The sample is then added on top. This mixture is then subjected to centrifugation — the spinning of the mixture at high speed to generate a "centrifugal force" that will lead to the formation of a concentration gradient of the molecule.
Components of the mixture will migrate to a point along this gradient with which its density is comparable. In this example, a specific type of lipid droplets, or small drops of fat molecules, was isolated from cells.
A homogenized mixture was first obtained by breaking the cells open. You've just watched JoVE's introduction the determination of the density of a liquid and a solid. You should now understand mass, volume, and density, as well as having a good idea of how to measure these quantities. Table 1 lists results for the determination of the density of ethanol using a mL volumetric flask.
Densities were calculated by dividing the measured mass by The mean measured density was 0. Table 2 lists results for the determination of the density of a sample of zinc metal using a mL graduated cylinder and the liquid displacement method. Note that the measured densities are constant within experimental error for both substances. Table 2 , in particular, demonstrates that density is independent of the amount of substance studied.
Table 1. Results for the determination of the density of ethanol using a mL volumetric flask. Table 2. Results for the determination of the density of a sample of zinc metal using a mL graduated cylinder and the liquid displacement method. Density is a characteristic intensive property of a substance. Thus, density measurements can be used to identify an unknown pure substance if a list of possible reference densities is available.
For example, density can be used to distinguish between metals similar in outward appearance Figure 2. In contexts where very low or very high mass is desirable, density is a critical material property. Materials engineers carefully consider the density of materials for construction in these contexts. For example, the bodies of some lightweight laptop computers are made of aluminum, one of the least dense metals. Lightweight tennis rackets contain titanium, another low-density metal.
Figure 2: Equivalent masses of aluminum Al and zinc Zn metal. The zinc metal occupies a much smaller volume due to its higher density. General Chemistry. Determining the Density of a Solid and Liquid. Try the instrument selector. Contact Sign in. Start Menu. Sign in. Menu Products. Products Menu. Product category.
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