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Measurement in Science

Measurement in Science. I can: Define precision and accuracy Differentiate between precision and accuracy Identify appropriate tool of measurement Use significant figures properly Measure and convert in the metric system. Uncertainty in Measurement.

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Measurement in Science

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  1. Measurement in Science • I can: • Define precision and accuracy • Differentiate between precision and accuracy • Identify appropriate tool of measurement • Use significant figures properly • Measure and convert in the metric system

  2. Uncertainty in Measurement • Accuracy – the closeness of a measurement to the true value • Precision – the reproducibility of a series of measurements

  3. good precision good accuracy good precision bad accuracy bad precision good accuracy Precision vs. Accuracy

  4. Learning Check 1 True(1) or false (2). Measurements can have poor accuracy and poor precision good accuracy and poor precision poor accuracy and good precision good accuracy and good precision Timberlake LecturePLUS 4

  5. Learning Check AP3 True(1) or false (2). Measurements can have poor accuracy and poor precision good accuracy and poor precision poor accuracy and good precision good accuracy and good precision 1 2 1 1 Timberlake LecturePLUS 5

  6. Match the following terms 1) Accuracy 2) Precision ___ How close a measurement is to the true value. ___ How close several measurements are to each other. Can you have data that are precise, but not accurate? Why or why not? Learning Check AP1 Timberlake LecturePLUS 6

  7. Match the following terms 1) Accuracy 2) Precision _1_ Is how close a measurement is to the true value. _2_ Is how close several measurements are to each other. Yes. Data can be precise, but not come close to the true value. Solution AP1 Timberlake LecturePLUS 7

  8. Learning Check AP2 How will each of the following affect accuracy and precision? 1. A meter stick that is missing the first centimeter. 2. A scale that has a zero point that is really five pounds above zero. Timberlake LecturePLUS 8

  9. Solution AP2 How will each of the following affect accuracy and precision? 1. The shortened meter stick will produce measurements that have poor accuracy, but good precision is possible. 2. The poorly calibrated scale will give a weight that is not accurate, but good precision is possible. Timberlake LecturePLUS 9

  10. Uncertainty In Measurements 6.4 6.3 6.35

  11. Uncertainty In Measurements

  12. Significant Figures • All measurements have some degree of uncertainty (depends on instrument used) • We usually report a measurement by recording all the certain digits plus the first uncertain (or estimated) digit • These numbers are called significant figures

  13. Counting Significant Figures

  14. 640 cm3 200.0 mL 0.5200 g 1.005 kg 10000 L 20.900 cm 0.00000056 g/L 0.04002 kg/m3 790001 cm2 665.000 kg•m/s2 Group Practice Determine the number of significant figures in the following measurements:

  15. Practice Answers  your work! • 2 • 4 • 4 • 4 • 1 • 5 • 2 • 4 • 6 • 6

  16. SI Units & Metric System

  17. Metric System • meter (m) – used to measure distance • liter (L) – used to measure volume (how much space an object takes up) • gram (g) – used to measure mass (amount of matter in an object) – NOT weight! • NOTE: weight is the force gravity applies to an object

  18. PneumonicDevice: king henry’s Daughters (mary, Laura & grace) drink chocolate milk Metric Prefixes kilo- 103 (k) hecto- 102 (h) deca- 101 (D) Meter (m) Liter (L) Gram (g) deci- 10-1 (d) centi- 10-2 (c) milli- 10-3 (m) How can I remember all those prefixes?

  19. Other Metric Prefixes • Sometimes very small amounts need to be measured • micro- μ 10-6 • nano- n 10-9 • pico- p 10-12

  20. Sample Abbreviations kg 1) kilograms = cL 2) centiliters = 3) Decameters = Dm 4) m = meters 5) hm = hectometers 6) dL = deciliter

  21. Making Conversions kilo- 1000 (k) hecto- 100 (h) Meter (m) Liter (L) Gram (g) deca- 10 (D) deci- 1/10 (d) centi- 1/100 (c) milli- 1/1000 (m) • find decimal • find beginning unit and end unit. • Which direction do you move? (right OR left) • How many spaces do you move? • move decimal (according to steps #3 & #4) 6.5m = ____ cm 650

  22. 9.341g = ____ mg 7400 cm = _____ hm 1.5 kL = _____ L 15 dm = _____ m 4.9 Dg = _____ g ANSWERS 9341 mg 0.74 hm 1500 L 1.5 m 49 g Practice

  23. International System of Units (SI) • Revised metric system proposed in 1960 • Widely used in science • Based on 7 fundamental units • All other units are derived from these 7 units

  24. Fundamental SI Units

  25. Derived Units in SI • Measured in terms of one or more fundamental SI unit • Examples: • Volume m x m x m = m3 = 1000 dm3 1 dm3 = 1 L • Density Mass / volume = kg/dm3 = g/cm3 = g/mL

  26. What do these measure?

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