Unit 3 Quiz Study Guide Precision of Physics

1. What is the density of a block of stone if it occupies 310. cm3 and has a mass of 853g? D = m/V = 853 g/310. cm3 = 2.75 g/cm3 2. Diamond has a density of 3.26 g/cm3. What is the mass of a diamond that has a volume of 0.351 cm3? m = V x D = 0.351 cm3 x 3.26 g/cm3 = 1.14 g 3. What is the volume of a sample of liquid mercury that has a mass of 76.2 g, given that the density of mercury is 13.6 g/cm3 V = m/D = 76.2 g/13.6 g/cm3 = 5.60 cm3 4. Determine the density in kg/m3, of a substance that has a mass of 84.7 g and occupies 49.6 cm3. (You will need to perform dimensional analysis to solve this problem!) 84.7 g x 10-3 kg = 0.0847 kg 49.6 cm3 x ( 1 m x 1 m x 1 m ) = 4.96 x 10-5 m3 102 cm 102 cm 102cm -5 3 D = m/V = 0.0847 kg/4.96 x10 m = 1710 kg/m3 Accuracy and Precision Indicate whether the following images are show accuracy and/or precision. 4. __ A _X_ P 5. __ A ___ P 6. _X_ A ___ P 7. _X_ A _X_ P Percent Error Calculate the indicated quantities and show all work. Round final answers to correct significant figures. 5. Pearce Perfect obtains the following measurements for the density of water: 1.03 g/mL, 1.45 g/mL, 0.640 g/mL. (a.) Calculate Pearce’s mean (average) density (1.03 + 1.45 + 0.640) /3 = 1.04 g/mL (b.) Calculate Pearce’s percent error if the actual density of water is 1.00 g/mL. Use the average from part a. (actual – measured)/actual x 100 = (1.00 – 1.04)/1.00 x 100 = 4.00% (c.) Was Pearce accurate/showing precision/neither/both? Explain. He was accurate because he had a low ` percent error, but he was not precise – his measurements were far away from each other. Evaluating Data for Accuracy and Precision According to the U.S. Mint, the mass of a U.S. quarter ($0.25) is 5.670g. Four students measured the same coin and recorded their results in Table B Table 1 – Measured Mass of U.S. Quarter 08/23/2010 Student I 5.010g 5.010g 5.011g 5.010g Avg= 5.010 g Student II 5.670g 5.589g 5.801g 5.712g Avg= 5.693 g Student III 5.673g 5.674g 5.669g 5.669g Avg= 5.671 g Student IV 5.669g 5.672g 5.671g 5.669g Avg= 5.670 g 6. Calculate the average of each data set and RECORD in the table. (Show an example calculation for one data set) (5.010 + 5.010 + 5.011 + 5.010)/4 = 5.010 g 7. Which data set (I, II, III, or IV) shows the most precision? Data Set 1 8. What information is required to determine the accuracy of any data set? The actual value (in this case, the mass of a quarter is 5.670 g) 9. Calculate the percent error for each student’s data set. (Show an example calculation for at least one data set). (5.670 – 5.010)/5.670 x 100 = 11.64% Student 1 Student 2: 4.056%, Student 3: 0.01764%, Student 4: 0.000% 10. Which data set is the most accurate? The data set of student __4__ is most accurate because ___he had the smallest percent error (0%)______ 11. Be able to define the following vocabulary words: Matter Mixture Colloid Chemical property Substance Heterogeneous Suspension Element Compound Homogeneous Solution Physical property (intensive and extensive) 12. Identify the following as elements, compounds or mixtures (what type of mixture?) a. b. c. d. i Phosphorous (P) E Air Mix - Homogeneous Sodium Hydroxide (NaOH) C A flower Mix - Heterogeneous j k e. f. g. h. Baking Soda (NaHCO3) C Cheesecake Mix - Homogeneous Silver (Ag) E Uranium (U) E l m I = Heterogeneous mixture of elements and compounds, J =compound, K = homogeneous mixture of elements, l = heterogeneous mixture of elements and compounds, m = element 13. Identify the following statements as physical or chemical properties of matter. a. Iron reacts with oxygen and forms rust – Chemical (actually a chemical change/reaction because it’s happening) b. The boiling point of water is 100 °C – Physical (intensive) c. Baking soda reacts with vinegar – Chemical d. The metal had a melting point of 95°C – Physical (intensive) e. The gas is flammable – Chemical f. Oxygen is a gas – Physical (intensive) g. Argon is not very reactive – Chemical h. Nickel has 4 isotopes – Physical (intensive) i. Nitrogen is a colorless gas – Physical (intensive) j. The silver spoons tarnished and turned dark – Chemical (actually a chemical change/reaction because it happened)