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Percent Error Sample Problem

Percent Error Sample Problem. A student measures the mass and volume of a substance and calculates its density as 1.40 g/mL. The correct, or accepted, value of the density is 1.30 g/mL. What is the percentage error of the student’s measurement?. Daily Inquiry: Monday, Sept. 17.

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Percent Error Sample Problem

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  1. Percent Error Sample Problem A student measures the mass and volume of a substance and calculates its density as 1.40 g/mL. The correct, or accepted, value of the density is 1.30 g/mL. What is the percentage error of the student’s measurement?

  2. Daily Inquiry:Monday, Sept. 17 • Record the length represented in the diagram below. • Record the volume of the liquid represented in the diagram below.

  3. Error in Measurement • Some error or uncertainty always exists in any measurement. • skill of the measurer • limitations of measuring instruments • When recording measurements, report all digits known for certain plus one last digit that is an estimate.

  4. Recording Measurements • Record the volume of liquid in the graduated cylinder to the correct number of digits.

  5. RULES FOR DETERMINING SIGNIFICANT FIGURES • Rule #1: Nonzero digits always count as significant figures: Examples: 438 g _____ sig fig 26.42 m _____ sig fig 1.7 cm _____ sig fig 2.653 L _____ sig fig

  6. Rule #2: Captive zeros always count as significant figures: Examples: 506 dm _____ sig fig 1005 mL _____ sig fig 900.43 kg _____ sig fig 20.006 cm _____ sig fig • Rule #3: Leading zeros do not count as significant figures: Examples: 0.8 g _____ sig fig 0.06 g _____ sig fig 0.0047 L _____ sig fig

  7. Rule #4: Trailing zeros are significant only if the number contains a decimal point: Examples: 60 g _____ sig fig 4830 km _____ sig fig 8.0 dm _____ sig fig 1.60 sec _____ sig fig 35.000 L _____ sig fig 0.002450 kg _____ sig fig

  8. RULES FOR ROUNDING NUMBERS • If the digit immediately to the right of the last significant figure you want to retain is: • Less than 5------ the last significant digit should stay the same. Example: Round 17.32 m to 3 significant figures. • Since the 2 is less than 5, you should round to __________ m

  9. 5 or greater --------- the last significant figure should increase by 1. Example: Round 42.68 g to 3 significant figures. • Since 8 is greater than 5, you should round to __________ g

  10. What Do You Think? • Determine the number of significant figures in each of the following: a. 12.045 d. 12.0 b. 0.0028 e. 0.500 c. 6500 f. 16.002070 2) Round each of the following to 2 significant figures. • 5.2836 b. 0.06382 c. 3196 3) Explain how the measurement 6.2 cm is different from 6.20 cm.

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