Slides - Unit 2

Slides - Unit 2 - Measurements & Mathematics...

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Unformatted text preview: Measurements & Mathematics Chemistry 102 Fall 2009 In the text s Chapter 1: b Sections 5-7 s Suggested Text Problems: b 13-16, 17, 18-40 (evens), 44, 48, 54-58 (evens), 62 2 Worksheets & Handouts . (on D2L) s Algebraic Methods for General Chemistry s Calculator Practice Problems s Metric System Using & Converting Units s Significant Figures Worksheet s Scientific Notation Worksheet 3 In this unit: s Accuracy & Precision s Rounding s Significant figures s Scientific notation s The metric system s Conversions, Density, Temperature 4 Accuracy how close a measurement is to the true value Precision how close a set of measurements are to each other accurate & precise precise but not accurate not accurate & not precise 1.8 5 Rounding s Count significant digits from the left side. s Round numbers. Dont truncate. s Only one digit determines the rounding. s The first digit in the number should be in the same decimal place after rounding as before rounding. Add place holding zeros if necessary. Round 0.0475 to 2 sig figs. Round 74.93 to 1 sig fig. Round 3,592.17 to 2 sig figs. Rounding answers to the correct number of significant figures 7 Rounding s The number to the right of the position you are rounding to determines how you round. b If 5 or greater, round to the next greatest number b If 4 or less, do not change 16 .93 rounded to ones place 17 = 16.9 3 rounded to tenths place 16.9 = 9 Identifying Significant Figures in Measurements Learn the following phrase: Point right, otherwise left Begin counting with the first nonzero number. If there is a decimal point present, count toward the right. If no decimal point count toward the left. After you begin counting count all non-zero digits to the end of the number. 10 How many significant figures are in each of the measurements below? Remember: Point right, otherwise left 467.24 0.006020 1250 0.00003 93,000,000 800 800. 11 Integers Ending in Zero (with no decimal point written). ? 25 ?? 8 00 ? ??? 10,34 0,000 Trailing zeros such as these may or may not be significant. It depends on whether they were measured or are just placeholders. Unfortunately you cant tell by looking. It is safest to assume they are NOT significant unless you know they are measured. 461 3 Significant Figures All nonzero numbers are significant. Significant Figures 16 401 3 Significant Figures A zero is significant when it is between nonzero digits. Significant Figures 17 A zero is significant when it is between nonzero digits. 5 Significant Figures 6 . 3 9 Significant Figures 18 3 Significant Figures 3 . 9 A zero is significant when it is between nonzero digits. Significant Figures 19 A zero is significant at the end of a number that includes a decimal point....
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This note was uploaded on 10/11/2009 for the course CHE 102 taught by Professor Maggie during the Fall '09 term at Wisc Whitewater.

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Slides - Unit 2 - Measurements & Mathematics...

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