1. chemistrySlide 1 of 48

2. 3.1Measurements and Their UncertaintyOn January 4, 2004, the Mars Exploration Rover Spirit landed on Mars. Each day of its mission, Spirit recorded measurements for analysis. In the chemistry laboratory, you must strive for accuracy and precision in your measurements. Slide 2 of 48 Copyright Pearson Prentice Hall 3. 3.1Measurements and Their Uncertainty>Using and Expressing MeasurementsUsing and Expressing Measurements How do measurements relate to science?Slide 3 of 48 Copyright Pearson Prentice Hall 4. 3.1Measurements and Their Uncertainty>Using and Expressing MeasurementsA measurement is a quantity that has both a number and a unit. Measurements are fundamental to the experimental sciences. For that reason, it is important to be able to make measurements and to decide whether a measurement is correct. Slide 4 of 48 Copyright Pearson Prentice Hall 5. 3.1Measurements and Their Uncertainty>Using and Expressing MeasurementsIn scientific notation, a given number is written as the product of two numbers: a coefficient and 10 raised to a power. The number of stars in a galaxy is an example of an estimate that should be expressed in scientific notation. Copyright Pearson Prentice HallSlide 5 of 48 6. 3.1Measurements and Their Uncertainty>Accuracy, Precision, and ErrorAccuracy, Precision, and Error How do you evaluate accuracy and precision?Slide 6 of 48 Copyright Pearson Prentice Hall 7. 3.1Measurements and Their Uncertainty>Accuracy, Precision, and ErrorAccuracy and Precision Accuracy is a measure of how close ameasurement comes to the actual or true value of whatever is measured. Precision is a measure of how close aseries of measurements are to one another.Slide 7 of 48 Copyright Pearson Prentice Hall 8. 3.1Measurements and Their Uncertainty>Accuracy, Precision, and ErrorTo evaluate the accuracy of a measurement, the measured value must be compared to the correct value. To evaluate the precision of a measurement, you must compare the values of two or more repeated measurements. Slide 8 of 48 Copyright Pearson Prentice Hall 9. 3.1Measurements and Their Uncertainty>Accuracy, Precision, and ErrorSlide 9 of 48 Copyright Pearson Prentice Hall 10. 3.1Measurements and Their Uncertainty>Accuracy, Precision, and ErrorDetermining Error The accepted value is the correct value based on reliable references. The experimental value is the value measured in the lab. The difference between the experimentalvalue and the accepted value is called the error. Slide 10 of 48 Copyright Pearson Prentice Hall 11. 3.1Measurements and Their Uncertainty>Accuracy, Precision, and ErrorThe percent error is the absolute value of the error divided by the accepted value, multiplied by 100%.Slide 11 of 48 Copyright Pearson Prentice Hall 12. 3.1Measurements and Their Uncertainty>Accuracy, Precision, and ErrorSlide 12 of 48 Copyright Pearson Prentice Hall 13. 3.1Measurements and Their Uncertainty>Accuracy, Precision, and ErrorJust because a measuring device works, you cannot assume it is accurate. The scale below has not been properly zeroed, so the reading obtained for the persons weight is inaccurate.Slide 13 of 48 Copyright Pearson Prentice Hall 14. 3.1Measurements and Their Uncertainty>Significant Figures in MeasurementsSignificant Figures in Measurements Why must measurements be reported to the correct number of significant figures?Slide 14 of 48 Copyright Pearson Prentice Hall 15. 3.1Measurements and Their Uncertainty>Significant Figures in MeasurementsSuppose you estimate a weight that is between 2.4 lb and 2.5 lb to be 2.46 lb. The first two digits (2 and 4) are known. The last digit (6) is an estimate and involves some uncertainty. All three digits convey useful information, however, and are called significant figures. The significant figures in a measurement include all of the digits that are known, plus a last digit that is estimated. Slide 15 of 48 Copyright Pearson Prentice Hall 16. 3.1Measurements and Their Uncertainty>Significant Figures in MeasurementsMeasurements must always be reported to the correct number of significant figures because calculated answers often depend on the number of significant figures in the values used in the calculation.Slide 16 of 48 Copyright Pearson Prentice Hall 17. 3.1Measurements and Their Uncertainty>Significant Figures in MeasurementsSlide 17 of 48 Copyright Pearson Prentice Hall 18. 3.1Measurements and Their Uncertainty>Significant Figures in MeasurementsInsert Illustration of a sheet of paper listing the six Insert Illustration of a sheet of paper listing the six rules for determining whether a digit in a measured rules for determining whether a digit in a measured value is significant. Redo the illustration as process value is significant. Redo the illustration as process art. Each rule should be a separate image. art. Each rule should be a separate image.Slide 18 of 48 Copyright Pearson Prentice Hall 19. Measurements and Their Uncertainty>Significant Figures in MeasurementsAnimation 2 See how the precision of a calculated result depends on the sensitivity of the measuring instruments.Slide 19 of 48 Copyright Pearson Prentice Hall 20. 3.1Measurements and Their Uncertainty>Significant Figures in MeasurementsSlide 20 of 48 Copyright Pearson Prentice Hall 21. Slide 21 of 48 Copyright Pearson Prentice Hall 22. Slide 22 of 48 Copyright Pearson Prentice Hall 23. Slide 23 of 48 Copyright Pearson Prentice Hall 24. Practice Problems for Conceptual Problem 3.1Problem Solving 3.2 Solve Problem 2 with the help of an interactive guided tutorial. Slide 24 of 48 Copyright Pearson Prentice Hall 25. 3.1Measurements and Their Uncertainty>Significant Figures in CalculationsSignificant Figures in Calculations How does the precision of a calculated answer compare to the precision of the measurements used to obtain it?Slide 25 of 48 Copyright Pearson Prentice Hall 26. 3.1Measurements and Their Uncertainty>Significant Figures in CalculationsIn general, a calculated answer cannot be more precise than the least precise measurement from which it was calculated. The calculated value must be rounded to make it consistent with the measurements from which it was calculated. Slide 26 of 48 Copyright Pearson Prentice Hall 27. 3.1Measurements and Their Uncertainty>Significant Figures in CalculationsRounding To round a number, you must first decide how many significant figures your answer should have. The answer depends on the given measurements and on the mathematical process used to arrive at the answer.Slide 27 of 48 Copyright Pearson Prentice Hall 28. SAMPLE PROBLEM 3.1Slide 28 of 48 Copyright Pearson Prentice Hall 29. SAMPLE PROBLEM 3.1Slide 29 of 48 Copyright Pearson Prentice Hall 30. SAMPLE PROBLEM 3.1Slide 30 of 48 Copyright Pearson Prentice Hall 31. SAMPLE PROBLEM 3.1Slide 31 of 48 Copyright Pearson Prentice Hall 32. Practice Problems for Sample Problem 3.1Problem Solving 3.3 Solve Problem 3 with the help of an interactive guided tutorial. Slide 32 of 48 Copyright Pearson Prentice Hall 33. 3.1Measurements and Their Uncertainty>Significant Figures in CalculationsAddition and Subtraction The answer to an addition or subtraction calculation should be rounded to the same number of decimal places (not digits) as the measurement with the least number of decimal places.Slide 33 of 48 Copyright Pearson Prentice Hall 34. SAMPLE PROBLEM 3.2Slide 34 of 48 Copyright Pearson Prentice Hall 35. SAMPLE PROBLEM 3.2Slide 35 of 48 Copyright Pearson Prentice Hall 36. SAMPLE PROBLEM 3.2Slide 36 of 48 Copyright Pearson Prentice Hall 37. SAMPLE PROBLEM 3.2Slide 37 of 48 Copyright Pearson Prentice Hall 38. Practice Problems for Sample Problem 3.2Problem Solving 3.6 Solve Problem 6 with the help of an interactive guided tutorial. Slide 38 of 48 Copyright Pearson Prentice Hall 39. 3.1Measurements and Their Uncertainty>Significant Figures in CalculationsMultiplication and Division In calculations involving multiplication anddivision, you need to round the answer to the same number of significant figures as the measurement with the least number of significant figures. The position of the decimal point has nothing to do with the rounding process when multiplying and dividing measurements.Slide 39 of 48 Copyright Pearson Prentice Hall 40. SAMPLE PROBLEM 3.3Slide 40 of 48 Copyright Pearson Prentice Hall 41. SAMPLE PROBLEM 3.3Slide 41 of 48 Copyright Pearson Prentice Hall 42. SAMPLE PROBLEM 3.3Slide 42 of 48 Copyright Pearson Prentice Hall 43. SAMPLE PROBLEM 3.3Slide 43 of 48 Copyright Pearson Prentice Hall 44. Practice Problemsfor Sample Problem 3.3Problem Solving 3.8 Solve Problem 8 with the help of an interactive guided tutorial. Slide 44 of 48 Copyright Pearson Prentice Hall 45. Section AssessmentAssess students understanding of the concepts in Section 3.1. Continue to:-or-Launch:Section QuizSlide 45 of 48 Copyright Pearson Prentice Hall 46. 3.1 Section Quiz 1. In which of the following expressions is the number on the left NOT equal to the number on the right? a. 0.00456 108 = 4.56 1011 b. 454 108 = 4.54 106 c. 842.6 104 = 8.426 106 d. 0.00452 106 = 4.52 109 Slide 46 of 48 Copyright Pearson Prentice Hall 47. 3.1 Section Quiz 2. Which set of measurements of a 2.00-g standard is the most precise? a. 2.00 g, 2.01 g, 1.98 g b. 2.10 g, 2.00 g, 2.20 g c. 2.02 g, 2.03 g, 2.04 g d. 1.50 g, 2.00 g, 2.50 gSlide 47 of 48 Copyright Pearson Prentice Hall 48. 3.1 Section Quiz 3. A student reports the volume of a liquid as 0.0130 L. How many significant figures are in this measurement? a. 2 b. 3 c. 4 d. 5 Slide 48 of 48 Copyright Pearson Prentice Hall 49. END OF SHOW