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# Class Note for CHM 115 at IPFW 3

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This 20 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at Indiana University taught by a professor in Fall. Since its upload, it has received 23 views.

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Date Created: 02/06/15

Measurement and Significant Figures Section 15 Measurement 1 MACROSCOPIC 2 Microscopic Anytime we report the results of a measurement we must include NUMERICAL VALUE UNTS Scientific Notation Section 15 otoln chemistry we often deal with numbers that are extremely large or extremely small For example In a liter of water there are about 33420000000000000000000000 H20 molecules Each molecule of H20 has a mass of about 00000000000000000000000299 grams Scientific Notation General Form A X 10n Where A mantissa is always 1 and lt 10 And n exponent is any positive or negative integer Express in scientific notation How many H20 molecules are there What is the mass of one H20 molecule Scientific Notation Examples Convert the following numbers to and from scientific notation 0007804 64234 764 x 10395 968 x 103 Error Analysis Section 15 ozoWnen making measurements it is not possible to obtain the exact value for the quantity under investigation This may be due to human error or instrument imperfection Width All measurements contain error 26 27 28 Let s measure the length and m width of this piece of cardboard using a ruler with graduations every 01 cm lil ue39l Width Length Precision versus Accuracy Section 15 otolf you repeat a particular measurement you usually do not obtain precisely the same result because each measurement is subject to experimental error Precision refers to the closeness of the set of values obtained from identical measurements of a quantity Accuracy refers to closeness of a single measurement to its true value Signi cant Figures Section 15 2Most numbers that we encounter are the result of a measurement and as a result are limited in their precision 2The method for expressing the precision of a measurement is in the number of signi cant gures we report Example Using two different meter sticks with different graduations determine the number of significant figures possible with each Significant Figures Cont F Uncertainty 67 101 i Iillllllllll7 675 i 001 How many significant figures are there for each of the above measurements 67 Sig Figs 675 Sig Figs Rules for Significant Figures Cont 1 All nonzero digits ARE significant 2 Zeros between nonzero digits ARE significant 3 Zeros to the LEFT of the first nonzero digit are NEVER significant 4 Numbers WITH decimal points a If a number is greater than 1 then all zeros to the right of the decimal point ARE significant b If a number is less than 1 then ONLY zeros that occur at the end of the number or between nonzero digits ARE significant 5 Numbers WITHOUT decimal points a Trailing zeros MAY or MAY NOT be significant This ambiguity is removed by expressing the number in scientific notation b Trailing zeros ARE significant if there is a decimal point Significant Figures Examples Number SIG FIGS Number SIG FIGS 2145 cm 400020 mL 11434 kg 4000 g 60608 m 40 x103 g 000043 g 250 L 000801 g 6606 x101O 01040510 g 200 mL 9 people exact 3100 kg Rounding Section 15 otoRounding consists of dropping all nonsignificant digits in a calculation and sometimes adjusting the last digit retained Rules A If the digit is greater than 5 add 1 to the last digit to be retained and drop all digits farther to the right B If the digit is less than 5 simply drop it and all digits farther to the right C If the digit is equal to 5 then if the preceding digit is even drop the five if the preceding digit is odd round up to next even digit Rounding Examples Round the following to 3 significant figures 3352 3357 1446 1444 1445 1455 Calculations with Significant Figures Section 15 A Addition and Subtraction report the result with the same number of decimal places as that of the number with the smallest number of decimal places B Multiplication and Division the number of significant figures in the final answer is determined by the original number having the fewest significant figures Calculations with Significant Figures Cont C Logs and antilogs 10quot See Special Experiment A log 18 x10395 474 10530 50 x10396 D Exact Numbers numbers that arise when you count items or when you define a unit infinite significant figures will not limit the number of significant figures in final answer defined quantities are exact E Chain Calculations AdditionSubtraction and MultiplicationDivision in doing a calculation of two or more steps retain nonsignificant digits for intermediate answers then ROUND only the final answer Calculations with Significant Figures Examples HW Problem 153 a 871gtlt 00301 2 0056 b 071 818 c 934 x 000435 107 d 84789 84773 x 14673 HW Problem 199 561 511 b 561511 a 658 658 c 91 86X2691 d 00065 x 321 00911 SI Units Section 16 Seven Base Units of the International System of Units SI Property Unit Symbol Length meter m Mass kilogram kg Time second 5 Temperature Kelvin K Amount of Substance mole mol Electric Current ampere A Luminous Intensity candela cd Table 12 page 21 Any property we wish to measure may be expressed in terms of these seven basic units or an appropriate combination of two or more SI Units Section 16 SI PREFIXES Factor Name Symbol Factor Name Symbol 103924 yocto y 101 deka da 103921 zepto z 1 02 hecto h 103918 atto a 103 kilo k 103915 femto f 106 mega M 103912 pico p 109 giga G 10399 nano n 1012 tera T 10396 micro p 1015 peta P 10393 milli m 1018 exa E 10392 centi c 1021 zetto z 10391 deci d 1024 yotto Y Table 13 page 22 SI Units Examples HW Problem 157 Write the following measurements using the appropriate SI prefix a 589X103912s b 02010m c 2560x10399s cl 605x103m HW Problem 1103 Write each of the following in terms of the SI base unit a 107 ps b 58 pm 0 319 nm cl 153 ms Temperature Conversions Section 16 SI Base unit is Kelvin K However we are usually more familiar with Fahrenheit F and Celsius C scales K m C F 373 H 100 A 212 Water boils 363 90 194 353 80 176 343 70 158 333 60 140 323 50 122 313 40 104 303 30 86 293 20 68 Roomtemperature 283 10 50 273 0 32 Waterfreezes 263 10 14 253 20 4 243 30 22 233 40 40 v Figure 123 page 24 Temperature Conversions Section 16 KelvinCelsius K C 27315 C K 27315 CelsiusFahrenheit c 59 F 32 F 95 C 32 Temperature Conversions Examples Convert 405 F into C Convert 45 C into K

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