Passage V

Students performed the following experiments to determine the density of common plastics.Experiment 1

A dry 100 mL graduated cylinder was placed on an electronic balance and tared (the balance was reset to 0.000 g). H₂O was added to the graduated cylinder until a certain mass was obtained. Ethanol was added to the graduated cylinder until the volume of liquid was 50.0 mL. The density of the liquid was then calculated. The procedure was repeated with different amounts of ethanol and H₂O (see Table 1).

Experiment 2

A known mass of potassium iodide (KI) was dissolved in a known mass of H₂O. A dry 100 mL graduated cylinder was placed on the balance and tared. The solution was added to the graduated cylinder until the volume was 50.0 mL. The density of the liquid was then calculated. The procedure was repeated with different amounts of KI and H₂O (see Table 2).

Experiment 3

A solid plastic bead was placed at the bottom of a sample of each of Liquids 1-10 from Experiments 1 and 2. If the bead stayed at the bottom, “S” was recorded in Table 3. If the bead rose, “R” was recorded in Table 3. The procedure was repeated for various plastics.