Lecture3 - Chem 1P Lecture 3: Units & Numbers Chang...

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Unformatted text preview: Chem 1P Lecture 3: Units & Numbers Chang Section 1.7 Measurements: units and numbers The result of a quantitative scientifc measurement is expressed in a number and a unit Chang Section 1.7 Tools: Units of Measurement International System (SI) based on the metric system Table 1.1 Fundamental units of the SI system Physical Quantity Mass Length Time Temperature El. Current Amount of substance Name of Unit kilogram meter second kelvin ampere mole Abbreviation kg m s K A mol Chang Section 1.7 Tools: Numbers Chang Section 1.7 mass The standard SI unit of mass is kilogram (kg) In chemistry, we often use the gram (g) as the practical unit for mass 1 kg = 1000 g = 1 x 103 g length The standard SI unit of length is meter (m) The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second Chang Section 1.7 volume Volume is derived from the unit of length (length3) The SI unit for volume is cubic meter (m3) 1 cm3 = (1 x 10-2 m)3 = 1 x 10-6 m3 1 dm3 = (1 x 10-1 m)3 = 1 x 10-3 m3 The cubic decimeter is also known as liter (L) 1 L = 1 dm3 = 1000 cm3 = 1000 mL Another useful relation is: 1 mL = 1 cm3 Chang Section 1.7 density The SI unit for density is kg/m3, but g/mL is more commonly used in chemistry 1 g/mL = 1 g/cm3 = 1 kg/dm3 = 1 kg/L Chang Section 1.7 density The density of copper is 8.96 g/mL. Calculate the volume of 15 g of copper. d= m V rearrange V= V= m d 15 g 8.96 g/mL = 1.68 mL = 1.68 cm3 Chang Section 1.7 time The SI unit for time is second (s) "The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom." Frequency The SI unit for frequency is Hertz (s) 1 Hz = 1 per second = 1 s-1 8.0 kHz = 8.0 x 103 per second Chang Section 1.7 temperature Chang Section 1.7 temperature TC = TK - 273.15 TC = (TF - 32 F) T F = TC x 9 F 5 C 5 C 9 F + 32 F How much is 98.6 F in Celsius degrees? TC = (98.6 F - 32 F) 5 C 9 F = 37.0 C Chang Section 1.8 Tools: scientific notation 2010 - 2011 annual salary $24,800,000.00 = $ 2.48 x 107 $0.0012 = $ 1.2 x 10-3 Convert the following numbers into scientific notation: 6,673,870.00 = 6.67387000 x 106 0.000483100 = 4.831 x 10-4 800.008 = 8.00008 x 102 Chang Section 1.8 Mathematical operations Adding and subtracting 3.03 x 10-2 + 1.34 x 10-1 = 0.303 x 10-1 + 1.34 x 10-1 = 1.64 x 10-1 6.77 x 103 - 9.34 x 102 = 6.77 x 103 - 0.934 x 103 = 5.84 x 103 Multiplying and dividing 1.2 x 102 x 7.8 x 104 = (1.2 x 7.8) x 10(2 + 4) = 9.4 x 106 8.96 x 103 x 1.55 x 10-1 = (8.96 x 1.55) x 10(3 - 1) = 13.9 x 102 = 1.39 x 103 9.7 x 104 9.7 = x 10(4-2) = 1.5 x 102 6.3 x 102 6.3 Chang Section 1.8 WileyPlus: Metric volume, area and density WileyPlus Example How many square femtometers are present in 0.731 square attometers? Express your answer in standard scientific notation. Definitions: 1 fm = 1 x 10-15 m 1 am = 1 x 10-18 m Conversion: 1 fm = 1000 am 1 fm2 = (1000)2 am2 = 1 x 106 am2 1 am2 = 1 x 10-6 fm2 Solution: 0.731 am2 = 0.731 x 10-6 fm2 = 7.31 x 10-7 fm2 Chang Section 1.8 WileyPlus: Metric volume, area and density WileyPlus Example How many cubic kilometers are present in 7.59 microliters? Express your answer in standard scientific notation. Definitions: 1 km3 = (1000)3 m3 = 1 x 109 m3 1 L = 1 x 10-6 L = 1 x 10-6 dm3 = 1 x 10-9 m3 Conversion: 1 m3 = 1 x 109 L 1 km3 = 1 x 109 x (1 x 109 L) = 1 x 1018 L 1 L = 1 x 10-18 km3 Solution: 7.59 L = 7.59 x 10-18 km3 See you on Friday! ...
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This note was uploaded on 11/23/2010 for the course CHEM Chem 1P taught by Professor Ericpotma during the Winter '10 term at UC Irvine.

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