1. review 35 mm = _______ dm _____ mm _____ km 0.25 dm3 = _____ cL = ______ cc Bromine heptafluoride _____ N2 S3 ________________________ Na2S 6500000 = ________ 0.00344 = __________ 3.6 X 10-3 x 6.1 X 10-6 = _____________ 3.6 X 10-3 / 6.1 X 10-6 = _____________
2. review 35 mm = 0.35 dm = 35000mm = 0.000035km 0.25 dm3 (L) = 25cL = 250 cc (mL) Bromine heptafluoride__BrF7___ N2 S3 dinitrogentrisulfide Na2S sodium sulfide 6500000 = 6.5 X 106 0.00344 = 3.44 X 10-3 3.6 X 10-3 x 6.1 X 10-6 = 21.96 X 10-9 = 2.2 X 10-8 3.6 X 10-3 / 6.1 X 10-6 = 0.59 X 103 = 5.9 X 102
3. Measurements are estimates Exact numbers Counted -- I have 3 sons Defined -- 4 qt in 1 gal Measured “exactness” limited by measuring device, object and user
4. Significant figures Measured and exact number Exact: Counted 13,000 people attended the conference 49 citizens attended the council meeting Defined 12 in = 1 ft, 2.54 cm = 1 in 1 kg = 2.2 lb NOT defined – remember weight changes!!! Measurements All are estimates – depend on precision of device
5. 16 oz = 1 lb, exact -- defined 2.54 cm = 1 in, exaact -- defined 454 g = 1 lb, measured 1.6 km = 1 mi not exact (rounded off for convenience) Actual exact number: 1 mi X 5280ft/mi X 12 in/ft X 2.54 cm/in = 160934 cm or 1.609344 km this would be the EXACT conversion Exact or measured??
6. Your reading might be 3.5 cm Measuring Estimate an Additional digit If possible If lines are very Close together May not be Practical!!! Your reading might be 4.55 – but on A real meter stick, you probably cannot Read between the mm lines Your reading should be 3.0 cm This means you think the real Value is between 2.9 and 3.1 Not between 2 and 4!!
7. Counting Significant Figures Number of Significant Figures 38.15 cm 5.6 ft 65.6 lb 122.55 m Complete: All non-zero digits in a measured number are (significant or not significant). Answers: 4,2,3,5
8. Leading Zeros Number of Significant Figures 0.008 mm 0.0156 oz 0.0042 lb 0.000262 mL Complete: Leading zeros in decimal numbers are (significant or not significant). Answers: 1,3,2,3
9. Sandwiched Zeros Number of Significant Figures 50.8 mm 2001 min 0.702 lb 0.00405 m Complete: Zeros between nonzero numbers are (significant or not significant). Answers: 3,4,3,3
10. Trailing Zeros Number of Significant Figures 25,000 in. 200 yr 48,600 gal 25,005,000 g Complete: Trailing zeros in numbers without decimals are (significant or not significant) if they are serving as place holders. Answers: 2,1,3,5
11. review 35 mm = _______ dm _____ mm _____ km 0.25 dm3 = _____ cL = ______ cc Bromine heptafluoride _____ N2 S3 ________________________ Na2S 6500000 = ________ 0.00344 = __________ 3.6 X 10-3 x 6.1 X 10-6 = _____________ 3.6 X 10-3 / 6.1 X 10-6 = _____________
12. review 35 mm = 0.35 dm = 35000mm = 0.000035km 0.25 dm3 (L) = 25cL = 250 cc (mL) Bromine heptafluoride__BrF7___ N2 S3 dinitrogentrisulfide Na2S sodium sulfide 6500000 = 6.5 X 106 0.00344 = 3.44 X 10-3 3.6 X 10-3 x 6.1 X 10-6 = 21.96 X 10-9 = 2.2 X 10-8 3.6 X 10-3 / 6.1 X 10-6 = 0.59 X 103 = 5.9 X 102
13. Measurements are estimates Exact numbers Counted -- I have 3 sons Defined -- 4 qt in 1 gal Measured “exactness” limited by measuring device, object and user
14. Significant figures Measured and exact number Exact: Counted 13,000 people attended the conference 49 citizens attended the council meeting Defined 12 in = 1 ft, 2.54 cm = 1 in 1 kg = 2.2 lb NOT defined – remember weight changes!!! Measurements All are estimates – depend on precision of device
15. 16 oz = 1 lb, exact -- defined 2.54 cm = 1 in, exaact -- defined 454 g = 1 lb, measured 1.6 km = 1 mi not exact (rounded off for convenience) Actual exact number: 1 mi X 5280ft/mi X 12 in/ft X 2.54 cm/in = 160934 cm or 1.609344 km this would be the EXACT conversion Exact or measured??
16. Your reading might be 3.5 cm Measuring Estimate an Additional digit If possible If lines are very Close together May not be Practical!!! Your reading might be 4.55 – but on A real meter stick, you probably cannot Read between the mm lines Your reading should be 3.0 cm This means you think the real Value is between 2.9 and 3.1 Not between 2 and 4!!
17. Counting Significant Figures Number of Significant Figures 38.15 cm 5.6 ft 65.6 lb 122.55 m Complete: All non-zero digits in a measured number are (significant or not significant). Answers: 4,2,3,5
18. Leading Zeros Number of Significant Figures 0.008 mm 0.0156 oz 0.0042 lb 0.000262 mL Complete: Leading zeros in decimal numbers are (significant or not significant). Answers: 1,3,2,3
19. Sandwiched Zeros Number of Significant Figures 50.8 mm 2001 min 0.702 lb 0.00405 m Complete: Zeros between nonzero numbers are (significant or not significant). Answers: 3,4,3,3
20. Trailing Zeros Number of Significant Figures 25,000 in. 200 yr 48,600 gal 25,005,000 g Complete: Trailing zeros in numbers without decimals are (significant or not significant) if they are serving as place holders. Answers: 2,1,3,5
21. HW Quiz Wed: metrics, sci not, naming HW problems: CH 1: 9-16-24, 61, 62 53 a,c (c volume displacement), 54 (density) Next class: classification of matter, chem and physical properties, (Ch3 sec 1 and Ch 5 sec 3) start conversion factors (Ch 1: sec 6,7,8) Check out mastering chemistry for problems!!
22. Learning Check A. Which answers contain 3 significant figures? 0.4760 2) 0.00476 3) 4760 B. All the zeros are significant in 1) 0.00307 2) 25.300 3) 2.050 x 103 C. 534,675 rounded to 3 significant figures is 1) 535 2) 535,000 3) 5.35 x 105 Answers: a: 2/3; b: 2/3; c: 2/3
23. Learning Check In which set(s) do both numbers contain the same number of significant figures? 1) 22.0 and 22.00 2) 400.0 and 40 3) 0.000015 and 150,000 Answer: #3
24. Learning Check State the number of significant figures in each of the following: A. 0.030 m1 2 3 B. 4.050 L 2 3 4 C. 0.0008 g 1 2 4 D. 3.00 m 1 2 3 E. 2,080,000 bees 3 5 7 29 people attended the conference ???EXACT Answers: a 2 b 4 c 1 d 3 e 3
28. Significant figures are needed for final answers from 1) adding or subtracting 2) multiplying or dividing
29. Adding and Subtracting The answer has the same number of decimal places as the measurement with the fewest decimal places. 25.2 gone decimal place + 1.34 gtwo decimal places 26.54 answer 26.5 one decimal place
30. Learning Check In each calculation, round the answer to the correct number of significant figures. A. 235.05 + 19.6 + 2.1 = 1) 256.75 2) 256.8 3) 257 B. 58.925 - 18.2 = 1) 40.725 2) 40.73 3) 40.7 Answers: a 2, b 3 Write vertically – calculators do not determine sig fig (84+ apps)
31. Multiplying and Dividing Round (or add zeros) to the calculated answer until you have the same number of significant figures as the measurement with the fewest significant figures. Or report in sci notation
32. Learning Check ? # sig fig? A. 2.19 X 4.2 = 1) 9 2) 9.2 3) 9.198 B. 4.311 ÷ 0.07 = 1)61.582) 62 3) 60 C. 2.54 X 0.0028 = 0.0105 X 0.060 1) 11.3 2) 11 3) 0.041 Answers: a 2, b 3, c 2
