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Rules for Determining Significant Figures AP Chemistry U01L05

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Objectives: 1.identify the number of significant figures expressed in measurements. 2.round measurements to specified numbers of significant figures. 3.express solutions to calculations with the correct number of significant figures. AP Chemistry U01L05

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Significant Figures Any quantity less than 1 must have a leading zero. AP Chemistry U01L05

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Rules for Determining Significant Figures 1.All nonzero digits are significant. Ex. measurement: 125 g – 3 significant figures Ex. measurement: 2 m – 1 significant figure AP Chemistry U01L05

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Rules for Determining Significant Figures 2.Zeros between nonzero digits are significant. Ex. measurement: 101 g – 3 significant figures Ex. Measurement: 1005 ml – 4 significant figures AP Chemistry U01L05

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Rules for Determining Significant Figures 3.For numbers -1: A zero to the left of a decimal point is not significant. This zero is referred to as a leading zero. Ex. measurement: 0.1 kg – 1 significant figure Ex. measurement: 0.25 km – 2 significant figures AP Chemistry U01L05

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Rules for Determining Significant Figures 4.AZeros To the right of a nonzero digit but to the left of an understood decimal point are not significant. Ex. measurement: 100 g – 1 significant figure Ex. measurement: 10 ml – 1 significant figure AP Chemistry U01L05

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Rules for Determining Significant Figures 4.B Zeros To the right of a nonzero digit but to the left of an expressed decimal point are significant. Ex. measurement: 100. g – 3 significant figures Ex. measurement: 10. m – 2 significant figures AP Chemistry U01L05

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Rules for Determining Significant Figures 5.For numbers -1: Zeros to the right of a decimal point and to the left of a nonzero digit are not significant. These zeros are referred to as placeholder zeros. Ex. measurement: 0.01 kg – 1 significant figure Ex. measurement: 0.001 L – 1 significant figure AP Chemistry U01L05

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Rules for Determining Significant Figures 6.All zeros to the right of a decimal point and a nonzero digit are significant. Ex. measurement: 1.0 g – 2 significant figures Ex. measurement: 1.00 g – 3 significant figures Ex. measurement: 1.000 g – 4 significant figures AP Chemistry U01L05

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Significant Figures and Calculations AP Chemistry U01L05

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Objectives: 1.express the results of calculations involving multiplication or division with the appropriate number of significant figures. 2.express the results of calculations involving multiplication or division with the appropriate number of significant figures. 3.round measurements and results of calculations to a specified number of significant figures. AP Chemistry U01L05

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Pg. 16 text AP Chemistry U01L05

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Pg. 16 text AP Chemistry U01L05

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Multiplication and Division The number of significant figures expressed in the final answer is the same as the least precise measurement used in the calculation. AP Chemistry U01L05

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Example 1 – Multiplication and Division Calculate the density of a sample of liquid substance with a mass of 5.00 g and a volume of 2.5 ml. AP Chemistry U01L05

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Addition and Subtraction The result has the same number of decimal places as the least precise measurement in the calculation. AP Chemistry U01L05

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Rules for Rounding In a series of calculations, always carry extra digits to the final result, then round the final answer. Determine at what decimal place the final answer is to be rounded. – If the digit immediately to the right is 4 or less the preceding digit stays the same. – If the digit immediately to the right is 5 or greater the preceding digit is increased by 1. AP Chemistry U01L05

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Example 1 – Addition and Subtraction Add the following masses. 30.01 g 10.0 g 20.01 g AP Chemistry U01L05

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Example 1 – Rounding Round each of the following measurements to 3 significant figures. 2.754 g/cm 3 2.757 g/cm 3 AP Chemistry U01L05

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Homework 1. Read textbook section 1.5 2. U01L05A1 pg. 34-35 #29-32, 35, 36 (33 points) AP Chemistry U01L05

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