131 1-31-2011
- 1. review35 mm = _______ dm _____ mm _____ km0.25 dm3 = _____ cL = ______ ccBromine heptafluoride _____N2 S3 ________________________Na2S6500000 = ________0.00344 = __________3.6 X 10-3 x 6.1 X 10-6 = _____________3.6 X 10-3 / 6.1 X 10-6 = _____________
- 2. review35 mm = 0.35 dm = 35000mm = 0.000035km0.25 dm3 (L) = 25cL = 250 cc (mL) Bromine heptafluoride__BrF7___N2 S3 dinitrogentrisulfideNa2S sodium sulfide6500000 = 6.5 X 1060.00344 = 3.44 X 10-33.6 X 10-3 x 6.1 X 10-6 = 21.96 X 10-9 = 2.2 X 10-83.6 X 10-3 / 6.1 X 10-6 = 0.59 X 103 = 5.9 X 102
- 3. Measurements are estimatesExact numbers Counted -- I have 3 sonsDefined -- 4 qt in 1 galMeasured“exactness” limited by measuring device, object and user
- 4. Significant figuresMeasured and exact numberExact:Counted 13,000 people attended the conference49 citizens attended the council meetingDefined12 in = 1 ft, 2.54 cm = 1 in 1 kg = 2.2 lb NOT defined – remember weight changes!!!MeasurementsAll are estimates – depend on precision of device
- 5. 16 oz = 1 lb, exact -- defined2.54 cm = 1 in, exaact -- defined454 g = 1 lb, measured1.6 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 conversionExact or measured??
- 6. Your reading might be 3.5 cmMeasuringEstimate anAdditional digitIf possibleIf lines are veryClose togetherMay not bePractical!!!Your reading might be 4.55 – but onA real meter stick, you probably cannotRead between the mm linesYour reading should be 3.0 cmThis means you think the realValue is between 2.9 and 3.1Not between 2 and 4!!
- 7. Counting Significant FiguresNumber 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 ZerosNumber of Significant Figures 0.008 mm 0.0156 oz 0.0042 lb 0.000262 mLComplete: Leading zeros in decimal numbers are (significant or not significant).Answers: 1,3,2,3
- 9. Sandwiched ZerosNumber of Significant Figures50.8 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 ZerosNumber of Significant Figures25,000 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. review35 mm = _______ dm _____ mm _____ km0.25 dm3 = _____ cL = ______ ccBromine heptafluoride _____N2 S3 ________________________Na2S6500000 = ________0.00344 = __________3.6 X 10-3 x 6.1 X 10-6 = _____________3.6 X 10-3 / 6.1 X 10-6 = _____________
- 12. review35 mm = 0.35 dm = 35000mm = 0.000035km0.25 dm3 (L) = 25cL = 250 cc (mL) Bromine heptafluoride__BrF7___N2 S3 dinitrogentrisulfideNa2S sodium sulfide6500000 = 6.5 X 1060.00344 = 3.44 X 10-33.6 X 10-3 x 6.1 X 10-6 = 21.96 X 10-9 = 2.2 X 10-83.6 X 10-3 / 6.1 X 10-6 = 0.59 X 103 = 5.9 X 102
- 13. Measurements are estimatesExact numbers Counted -- I have 3 sonsDefined -- 4 qt in 1 galMeasured“exactness” limited by measuring device, object and user
- 14. Significant figuresMeasured and exact numberExact:Counted 13,000 people attended the conference49 citizens attended the council meetingDefined12 in = 1 ft, 2.54 cm = 1 in 1 kg = 2.2 lb NOT defined – remember weight changes!!!MeasurementsAll are estimates – depend on precision of device
- 15. 16 oz = 1 lb, exact -- defined2.54 cm = 1 in, exaact -- defined454 g = 1 lb, measured1.6 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 conversionExact or measured??
- 16. Your reading might be 3.5 cmMeasuringEstimate anAdditional digitIf possibleIf lines are veryClose togetherMay not bePractical!!!Your reading might be 4.55 – but onA real meter stick, you probably cannotRead between the mm linesYour reading should be 3.0 cmThis means you think the realValue is between 2.9 and 3.1Not between 2 and 4!!
- 17. Counting Significant FiguresNumber 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 ZerosNumber of Significant Figures 0.008 mm 0.0156 oz 0.0042 lb 0.000262 mLComplete: Leading zeros in decimal numbers are (significant or not significant).Answers: 1,3,2,3
- 19. Sandwiched ZerosNumber of Significant Figures50.8 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 ZerosNumber of Significant Figures25,000 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. HWQuiz Wed: metrics, sci not, namingHW problems: CH 1: 9-16-24, 61, 6253 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 CheckA. 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 103C. 534,675 rounded to 3 significant figures is1) 535 2) 535,000 3) 5.35 x 105Answers: a: 2/3; b: 2/3; c: 2/3
- 23. Learning CheckIn 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 150,000Answer: #3
- 24. Learning CheckState 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 ???EXACTAnswers: a 2 b 4 c 1 d 3 e 3
- 25. Significant Numbers in CalculationsHelp you decide where to round a number from your calculator
- 26. A calculated answer cannot be more precise than the measuring tool.
- 27. A calculated answer must match the least precise measurement.
- 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 CheckIn 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) 40.7Answers: a 2, b 3Write 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) 0.041Answers: a 2, b 3, c 2