<p>Chapter 1, cont’d: Units of Measurement</p><p>Measured quantities are associated with units!!</p><p>1. Base units in the SI system:</p><p>Mass kilogram (kg) Length meter (m) Time sec (s) Quantity mole (mol) Temperature Kelvin (K)</p><p>From the base units come derived units, e.g., Density = mass/volume Velocity = distance/time</p><p>9 Review of Exponential Notation (Appendix A1) e.g., express the following in scientific notation: 0.001453 m3 (what is this a measure of?) 33987.22 sec</p><p>SI system uses prefixes to indicate decimal fractions or multiples of units, e.g., </p><p>Kilo- k 1x103</p><p>Centi- c 1x10-2 </p><p>Milli- m 1x10-3 </p><p>Micro-  1x10-6 </p><p>Nano- n 1x10-9</p><p>LOOK OVER TABLE 1.5 (Common SI Prefixes)</p><p>10 e.g., use appropriate metric prefixes (k-, p, n, etc) to express the following measurements without an exponent:</p><p>6.5 x 10-9 m</p><p>3.5 x 103 L</p><p>6.54 x 105 s</p><p>Temperature What is temperature? Temperature scales Celsius</p><p> o 0 C= freezing point of H2O</p><p> o 100 C=boiling point of H2O (at sea level)</p><p>-What are the corresponding temps in oF?</p><p>Conversions between oC and oF</p><p> oC = 5/9(oF - 32o)</p><p> oF = 9/5(oC) + 32o</p><p>11 Kelvin scale</p><p>0 K = -273.15 oC (absolute zero)</p><p>K = oC + 273.15</p><p>Density (D) D = mass / volume</p><p>What are the base SI units of density?</p><p>More common: units of g/cm3 -Do density and weight describe the same thing? Is density an intensive property of matter or an extensive one?</p><p>Calculations using density</p><p>Find the density (g/cm3) of Hg if 1.00x102 g of this substance occupies a volume of 7.45 cm3</p><p>12 2. Uncertainty in Measurement Uncertainties always exist in measured quantities. Why?</p><p>Exact and Inexact Numbers Exact: any counted quantity; any conversion factor Inexact: any measured quantity</p><p>Precision and Accuracy precision: how closely individual measurements agree with each other</p><p> accuracy: how closely individual measurements agree with the "correct" value</p><p>Significant Figures Measured quantities are reported such that only the last digit is uncertain</p><p>13 e.g., a penny has a mass of 1.5576 g. This implies that the uncertainty in the mass of the penny is  0.0001 g.</p><p>How many significant figures are reported in the mass of the penny?</p><p>How do we determine the number of significant figures in a measured quantity? Rules to live by: all nonzero digits are significant (893 cm ; 17.57 L)</p><p> zeros between nonzero digits are significant (1.005 mol; 104 kg)</p><p> zeros to the left of the first nonzero digit are NOT significant (0.05 mol)</p><p> zeros at the end of a number AND to the right of the decimal point ARE significant (0.0200 mol; 3.0 cm)</p><p>14 OK, what about a number which ends in zeros that are not to the right of the decimal point? (120g, 11500 cm) write the number in scientific notation:</p><p> e.g., 120 g = 1.20x102 g (3 sig figs)</p><p>11500 cm = 1.1500x104 cm (5 sig figs) </p><p>Significant figures in calculations involving measured quantities The precision of the calculated result is limited by the least precise measurement!!!!! </p><p>Multiplication and division result must have no more sig figs than the measurement with the fewest sig figs e.g.: Suppose that a 1.05 g sample of a metal had a volume of 23.610 cm3. Find the density in g/cm3. </p><p>15 If the result has more than the correct number of sig figs, it must be rounded off: e.g., round 0.006543210 nm to four sig figs and report in scientific notation </p><p>In calculations with intermediate steps, retain an extra sig fig or two through the calculations and round the final result to the correct number of sig figs!</p><p> e.g.: The maximum allowable concentration of CO in urban air is 10.0 mg/m3 over an 8-hour period. At this level, what mass of CO in mg is present in a room measuring 8.0 x 12.1 x 10.1 m?</p><p>3. Dimensional Analysis/Conversions Length Given that 1 m = 1.0936 yd, and 1 inch = 2.54 cm, how many inches are in 2.5 m?</p><p>16 Convert 0.0023 mm to nm</p><p>Volume</p><p>SI unit of volume = m3</p><p>More common: cm3 (or cc) or dm3 1 liter (L) = 1000 ml = 1000 cm3 Given that 1 L = 1.057 qt, how many L is 5 gal of gasoline?</p><p>Convert 55.35 ft3 to cm3</p><p>17 The density of air is 1.19 g/L. What is the mass, in kg, of the air in a room that measures 12.5 x 15.5 x 8.0 ft?</p><p>18 Problems du Jour</p><p>Perform the following conversions: 5.0 x 10-8 m to nm</p><p>1.55 kg/m3 to g/L</p><p>5.0 pm/s to m/s</p><p>An individual suffering from high blood cholesterol has a count of 232 mg cholesterol/100 mL blood. If the total blood volume is 5.2 L, how many g of total blood cholesterol does this person contain? </p><p>19</p>