Density, Temp, and Scientific Notation Wednesday, September 09, 2009 8:23 AM Density, Temperature, and Scientific Notation FYI: You may need to look up the density values for various substances in some of these questions. Your textbook is a good place to start ;) 1. Pumice is a volcanic rock that contains many trapped air bubbles. A 155-g sample is found to have a volume of 163 mL. a) What is the density of pumice? 155g/163 mL = .951 g/mL b) What is the volume of a 4.56-kg sample? c) Will pumice float or sink in water? In ethyl alcohol? Density Water = 1.00 g/mL Float in water Density Ethanol = .789 g/mL Sink in ethanol 2. A small box is filled with liquid mercury. The dimensions of the box are 3.00 cm wide, 8.50 cm long, and 6.00 cm high. What is the mass of the mercury in the box? (1.00 mL = 1 cm3) V = 3.00 cm x 8.50 cm x 6.00 cm = 153 cm 3 Density Mercury = 13.546 g/mL D = m/V --> m = DV m= 13.546 g/mL x 153 cm 3 = 2.07 x 10 3 g 3. The volume of liquid in a graduated cylinder is 14.00 mL. When a certain solid is added, the volume reads 92.45 mL. The mass of the solid is 136.5 g. What might the solid be? Volume = 92.45 mL - 14.00 mL = 78.45 mL D = 136.5g ÷ 78.45 mL = 1.740 g/mL Kerosene 0.82 g/mL Aluminum 2.70 g/mL Ice (0°C) 0.92 g/mL Magnesium 1.74 g/mL Lead 11.3 g/mL Table salt 2.16 g/mL 4. Mercury thermometers cannot be used in cold arctic climates because mercury freezes at -39°C. What is this temperature in degrees Fahrenheit? 5. Convert the following temperatures to the Kelvin or Celsius scale. a) 175 K b) 47°C c) 300 K d) -12°C ChemH HW Answers Page 1 d) -12°C 6. Express the following numbers in scientific notation. a) 423,000 4.23 x 105 b) 433.8 4.338 x 10 2 c) 0.0020 2.0 x 10-3 d) 0.00000106 1.06 x 10-6 7. Without a calculator, carry out each of the following operations. a) (1.42 x 10-10) + (0.17 x 10-10) + (1.43 x 10-9) b) (299 x 1010) + (823 x 108) + (0.75 x 1011) c) (7 x 10-5) x (8 x 10-6) d) (1.8 x 10-4) ÷ (3.0 x 10-2) Adapted from Basic Concepts of Chemistry by Leo J. Malone ChemH HW Answers Page 2

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