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Science TAKS: Bell Ringers Prepared for the Scurry-Rosser High School Science Department Objective 4, I.07A Investigate and identify properties of fluids including density, viscosity, and buoyancy. Important Definitions • Buoyancy - The force that causes objects to float. According to the principle of Archimedes, when a solid is placed in a fluid (a liquid or a gas), it is subject to an upward force equal in magnitude to the weight of the fluid it has displaced. • Density - A measure of the quantity of some physical property (usually mass) per unit length, area, or volume (usually volume). – Mass density is a measure of the mass of a substance per unit volume. Most substances (especially gases such as air) increase in density as their pressure is increases or as their temperature decreases. – Energy density is a measure of the amount of energy (often in the form of electromagnetic radiation) per unit volume in a region of space or some material. – Population density is the number of individuals, such as inhabitants or housing units, per unit of area. • Viscosity - The resistance of a substance to flow. – For example, water has a lower viscosity than molasses and flows more easily. #1) A block of maple wood with a volume of 405 cubic centimeters and a density of .67 g/cm3 is sawed in half. The density of the two smaller blocks is now A. one-fourth the original density B. one-half the original density C. two times the original density D. the same as the original density State Average: 31% correct #2) This pipette is filled with a 20% NaOH solution. The solution is at 20oC and has a density of 1.23 g/mL. According to this information, what is the mass of this NaOH solution? F. 3.88 g G. 15.7 g H. 23.9 g J. 24.6 g State Average: 53% correct #3) Swimmers find that they can float more easily in the ocean than in a freshwater pond. The most likely reason for this phenomenon is that the A. viscosity of pond water is greater than that of ocean water. B. density of ocean water is higher than that of pond water. C. temperature of pond water is lower than that of ocean water. D. mass of ocean water is greater than that of pond water. State Average: 53% correct #4) A sample of an element has a volume of 78.0 mL and a density of 1.85 g/mL. What is the mass in grams of the sample? Record and bubble in your answer to the nearest tenth on the answer document. ___ ___ ___ . ___ ___ ___ State Average: 56% correct Use the information below and your knowledge of science to answer questions #42-44 • Soap-Making Project Materials: • 125 mL cooking oil • Safety goggles • Stirring rod • 100 mL H2O • Apron • 10 g NaOH • 500 mL beaker Procedure: • Measure and add 100 mL of H2O to 125 mL of cooking oil and mix thoroughly. • Carefully and slowly add 10 g of NaOH while stirring constantly. • Stir until a thick paste forms. • Pour the paste into a mold and let it sit for two days. • Remove the solid bar from the mold. Caution: Keep this soap away from the face and eyes because traces of NaOH may still be present on the soap bar. Use this soap for washing floors and tools only. #5) A bar of soap produced by this soapmaking process normally sinks to the bottom of a container of water. Which of these processes could cause the bar of soap to float in water? A. Making grooves in the surface of the thick paste. B. Adding air bubbles to the thick paste. C. Letting the thick paste sit for four days. D. Chilling the mold filled with the thick paste. State Average: Tested Oct-2005 TAKS Question Set Answers • • • • • #1 #2 #3 #4 #5 D C B 144.3 g B