Lecture_03_100311 - Lecture 3: Significant Figures Goal:...

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Lecture 3: Significant Figures Goal: Determine the number of significant figures in measured numbers and use this information to adjust calculated answers to the correct number of significant figures Outline (Timberlake Chapter 1.3-1.4): ± Measured Numbers and Significant Figures (1.3) ± Significant Figures in Calculations (1.4) Problems for Extra Practice: 1.5, 1.7, 1.9, 1.13. 1.15. 1.17, 1.19, 1.21
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Measured Numbers vs. Exact Numbers Measured numbers are obtained when you measure a quantity – Example: measure your height, weight or temperature Exact numbers are obtained by counting items or from a definition – Example: counting 24 students in the lab definition 1 kg is equal to 1000 g 1 ft is equal to 12 in. – Not measured, do not have a limit on the number of significant figures and do not affect the number of significant figures in a calculation
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. l 2 . . . . l . . . . l 3 . . . . l . . . . l 4 . . cm Reading a Meter Stick • The markings on the meter stick at the end of the blue line are read as The first digit 2 plus the second digit 2.7 • The last digit is obtained by estimating. • The end of the line might be estimated between 2.7 and 2.8 as 0.05 or 0.06, which gives a reported length of 2.75 cm or 2.76 cm.
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Known + Estimated Digits In the length reported as 2.76 cm: The digits 2 and 7 are certain ( known ). The final digit 6 was estimated ( uncertain ). All three digits (2.76) are significant , including the estimated digit.
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. l 8 . . . . l . . . . l 9 . . . . l . . . . l 10 . . cm What is the length of the red line? 1)
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This note was uploaded on 01/18/2012 for the course CHEM 120A taught by Professor Leahmiller during the Fall '11 term at University of Washington.

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Lecture_03_100311 - Lecture 3: Significant Figures Goal:...

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