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Significant Figures: Precision and Accuracy in Measurement

Significant Figures: Precision and Accuracy in Measurement. Target Practice. 9 mm pistol. Was the shooter accurate? Was the shooter precise? Why or why not?. Ruger Mark II Competion Target Pistol. Was the shooter accurate? Was the shooter precise? Why or why not?.

sybill-velasquez
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Significant Figures: Precision and Accuracy in Measurement

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  1. Significant Figures: Precision and Accuracy in Measurement

  2. Target Practice

  3. 9 mm pistol

  4. Was the shooter accurate?Was the shooter precise?Why or why not?

  5. Ruger Mark II Competion Target Pistol

  6. Was the shooter accurate?Was the shooter precise?Why or why not?

  7. Chandler Sniper M40 Long Range Precision Rifle

  8. Was the shooter accurate?Was the shooter precise?Why or why not?

  9. Precise Accurate and Precise

  10. So, what do precision and accuracy mean in your labs? • Precision is how close your lab measurements are to each other • Accuracy is how close your measurements are to the correct value.

  11. How do we express accuracy in measurement? • We record the measurement according to the accuracy of the equipment used plus one estimated digit. Least accurate 76.0 mL Meniscus What is the correct reading for the cylinder on the left? 21.50 mL Answer: 73.0 mL Most accurate Estimate one digit between the lines. 6.62 mL

  12. Which balance is more accurate? Estimated digit

  13. Rules for Significant Figures

  14. Rule 1: Nonzeros are always signficant. Examples: 4.56 23 11,526 • 3 SF • 2 SF • 5 SF

  15. Zeros are the problem!! • There are 3 kinds of zeros: • CAPTURED: in the middle • PRECEDING: on the left • TRAILING: on the right

  16. Rule 2:CAPTURED zeros are ALWAYS significant. Examples: 101 200,205 7802 • 3 SF • 6 SF • 4 SF

  17. Rule 3:PRECEDING zeros are NEVER significant. Examples: 0.00101 0.200205 0.00007802 • 3 SF • 6 SF • 4 SF

  18. Rule 4:TRAILING zeros are significant WITH A DECIMAL present. Examples: 100 100. 0.5000 105.75060 • 1 SF • 3 SF • 4 SF • 8 SF Challenge: Write one hundred in 2 SF.

  19. Significant Figures in Calculations

  20. Multiplying and Dividing • Rule 5: When multiplying or dividing the answer will have the same SF as the least accurate measurement. Example: m = 9.567 g V = 10.1 mL D = m/V = 9.567g/10.1 mL = = Note the use of Given, Formula, Substitute, Solve 3 SF 0.9472277228 g/mL 0.947 g/mL

  21. Rule 6: Counted, known, and accepted values DO NOT affect significant figures. Example: (20 students)(68.18 kg avg. mass) = 1363.6 kg Round answer to 4 sig figs. = 1364 Kg Counted value has no affect Least accurate measurement

  22. Adding and Subtracting • Rule 7: When adding and subtracting, the answer is rounded to most accurate decimal place shared by all the measurements. Example: 209.7 cm 8.004 cm + 1012.39 cm 1230.094 cm Tenths column is the most accurate decimal place shared by all the measurements, so round to tenths. Final answer: 1230.1 cm

  23. Tha…tha…tha…that’s all folks! …for now…

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