1. CHAPTER 3: MEASUREMENT

2. ACCURACY AND PRECISION

3. Can never be exact Instrument marking can’t be fine enough Defective instrument Environmental conditions Use or read the instrument incorrectly The Limits of Measuring p. 563.6PHYSICAL SCIENCE

4. How many measurements are exactly on the scale division? Almost None!

5. 89 ABCDE A. 8.13 cm B. 8.50 cm C. 8.62 cm A. 8.13 cm B. 8.50 cm C. 8.62 cm D. 8.80 cm E. 9.00 cm D. 8.80 cm E. 9.00 cm Ruler

6. 0.70.8 ABCDE A. 0.715 g B. 0.740 g C. 0.758 g A. 0.715 g B. 0.740 g C. 0.758 g D. 0.773 g E. 0.800 g D. 0.773 g E. 0.800 g Balance

7. 34 ABCDE A. 3.15 g B. 3.40 g C. 3.58 g A. 3.15 g B. 3.40 g C. 3.58 g D. 3.73 g E. 4.00 g D. 3.73 g E. 4.00 g Balance

8. A B C D 20 30 Graduated Cylinder A. 28.5 mL B. 25.0 mL C. 24.0 mL D. 21.3 mL A. 28.5 mL B. 25.0 mL C. 24.0 mL D. 21.3 mL

9. A B C D 2 3 A. 2.9 mL B. 2.5 mL C. 2.4 mL D. 2.2 mL A. 2.9 mL B. 2.5 mL C. 2.4 mL D. 2.2 mL Graduated Cylinder

10. D C B A 20 30 Thermometer A. 24.5 °C B. 28.0 °C C. 30.0 °C D. 33.7 °C A. 24.5 °C B. 28.0 °C C. 30.0 °C D. 33.7 °C

11. A B C D Beaker A. 85 mL B. 60 mL C. 40 mL D. 23 mL A. 85 mL B. 60 mL C. 40 mL D. 23 mL 20 40 60 80

12. The accuracy of a measurement is an assessment of the measurement error The instrument and the user can also affect the accuracy Accuracy p. 573.7PHYSICAL SCIENCE

13. accurate but not precise

14. Precision is an assessment of the exactness of a measurement When measuring with a metric instrument, estimate the measurement to 1/10 of the smallest decimal subdivision on the instrument scale Precision pp. 57-583.8PHYSICAL SCIENCE

15. precise but not accurate

16. accurate and precise

17. Scientists evaluate the usefulness of their measurements by repeating them as many times as needed to see how they vary Random errors Systematic errors Repeatability p. 583.9PHYSICAL SCIENCE

18. Significant Digits Using the concept of significant digits (SD), scientists have a way to indicate the precision of their measurements pp. 59-613.10PHYSICAL SCIENCE

19. Identifying Significant Digits SD Rule 1: SDs apply only to measured data SD Rule 2: All nonzero digits in measured data are significant SD Rule 3: All zeros between nonzero digits are significant pp. 59-613.10PHYSICAL SCIENCE

20. SD Rule 4: Decimal points define significant zeros SD Rule 5: A decimal point must follow an estimated zero in the one’s place pp. 59-613.10PHYSICAL SCIENCE

21. Convert very large or small numbers into a product of a small number and a power of ten M × 10 n 1 ≤ M < 10; n is an integer Scientific Notation p. 613.11PHYSICAL SCIENCE

22. Scientific Notation and Significant Digits According to SD Rule 4B, how many SDs does the measurement 3800 mm have? 3800 mm (WRONG!) 3.80 × 10 3 mm (RIGHT!) p. 613.11PHYSICAL SCIENCE

23. Scientists have developed sophisticated methods for identifying the significant digits in calculated results Become familiar with the rules in Appendix E Math with Measurements p. 623.12PHYSICAL SCIENCE

24. Mechanical tolerance—the “wiggle room” in parts that are made to fit together Engineers express tolerance as the desired dimension plus or minus (±) Using Measurements p. 623.13PHYSICAL SCIENCE