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KWL STRATEGY

KWL STRATEGY. K (what do you know W (what do L (what About Measurement) you want to have you know learned) about Measurement. CH. 2 Precision & Accuracy , % error, Metrics, Measurement & Significant Figures. Precision vs. Accuracy.

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KWL STRATEGY

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  1. KWL STRATEGY K (what do you know W (what do L (what About Measurement) you want to have you know learned) about Measurement

  2. CH. 2 Precision & Accuracy ,% error, Metrics, Measurement & Significant Figures

  3. Precision vs. Accuracy In the context of the scientific method, precision and accuracy have two distinctly different meanings. • The accuracy of a measurement system is the degree of closeness of measurements of a quantity to its actual (true)value. • The precision of a measurement system is the degree to which repeated measurements under unchanged conditions show the same results. See dartboard (p. 44) • A measurement system can be accurate but not precise, precise but not accurate, neither, or both.

  4. Visualizing the concept • www.yorku.ca/psycho/en/pics_en/postscript_f1.gif

  5. CALCULATING % ERROR % error = measured – accepted accepted X 100 p. 45 #1 practice problem Find the % error if a mass measurement is 17.7 grams when the correct mass is 21.2 grams.

  6. Example 2 • A liquid’s volume is measured in a beaker as 40 mL. It is then measured in a graduated cylinder as 45.5 mL. Find the % error.

  7. P. 45 # 1—2

  8. p. 60 #35—37

  9. % error problems 1. 0.9% 2. 0.4% 3. 3.5% 4. 9.3% 5. 1.7% 6. 3.7% 7. 0.3% 8. 10.4%

  10. MEASUREMENT WARM UP • 1. Based on the following data collected, comment on this person’s accuracy & precision: • ***Volume in beaker trial 1= 30.0 mL Trial 2 = 31.0 Trial 3= 31. 5 • ***Volume in cylinder = 45.5 mL • 2. Calculate % error: A student measures mass as 50.9 grams. The instructor measures 55.9 grams.

  11. 1. high precision; low accuracy • 2. 8.9%

  12. WRITING ACTIVITY--ACTIVATOR Write a paragraph to your friend explaining to him or her the difference between accuracy vs. precision. Include an example using the dartboard analogy. (refer to p. 44 if needed)

  13. QUIZ CALCULATE % ERROR FOR THE FOLLOWING: 1. A student measures the volume of a cube to be 20.5 cubic centimeters. He checks this against the correct volume which is 25 cubic centimeters. 2. A liquid’s volume is 35 mL in a graduated cylinder, while in a beaker the volume is 25 mL. 3. Comment On precision And accuracy For picture D.

  14. IPAD ACTIVITY—Introduction to Metrics http://www.brookscole.com/math_d/special_features/ext/internet_activities/matovina/metric ONLY COMPLETE 1—6 and #8 TODAY USE YOUR OWN NOTEBOOK PAPER

  15. ACTIVATOR: Why is the metric system of measurement (which uses meters, liters, grams, etc.) preferred AND easier to use rather than the English system of measurement (which uses pounds, feet, etc.)?

  16. ENGLISH SYSTEM UNITS: • 1 foot. = 12 inches • 1 pound = 16 ounces • 1 cup = 8 ounces • 1 yard = 3 feet • 1 mile = 5280 feet

  17. METRIC SYSTEM • Also known as the SI based system (International System of Measurements) • It is more preferred rather than the English system of measurements because it is based on units of 10. • Measurement systems are all based on “standards” which are physical representations for each measurement unit. • We will learn about the prefixes “Tera” through “pico”. (see chart)

  18. METRIC QUANTITIES AND WHAT UNITS THEY ARE MEASURED IN:(see p. 34 in your textbook) Mass = gram Distance = meter Volume = liters or cubic meter Time = seconds Temperature = Kelvin Amount of a substance = mole Electric current = ampere Light intensity = candela Area = square meter Energy = joule

  19. ADDING PREFIXES TO BASE UNITS • 1 KILOmeter = ________________meters • 1 CENTIgram = ______________________grams • 1 millisecond = __________________seconds

  20. THE METRIC LINE(STAIRCASE)

  21. METRIC ACRONYM • THE • GREAT • MIGHTY • king • henry • died • by • drinking • chocolate • milk • maybe • not • pasteurized

  22. TELL WHAT EACH SYMBOL STANDS FOR: mg kL Mm mm um m

  23. METRIC CONVERSIONS

  24. ACTIVATOR: 3-2-1 Name 3 basic metric units. Name 2 prefixes AND give their symbol. Name 1 thing you know about a “standard” of measurement.

  25. 3 ways for measuring volume: 1. liquids—graduated cylinder (measures in mL) 2. rectangular shaped solids- use a ruler for length x width x height (measured in cubic cm or cm3 or cc) • Irregular shaped solids—water displacement ***VOLUME—the amount of space something takes up

  26. YOU TRY: 25 mL = ___________________cc (cm3) 25 cc = ________________________L

  27. METRIC HANDOUT • 1—12, 15, 16

  28. SUMMARIZER: Describe how you would take the volume of a glass of water, a rectangular block, and a marble. Also, tell what units that you would use to measure each.

  29. WRITING ASSIGNMENT: • (1-2 paragraphs) • Discuss the differences between area & volume. Include in your discussion: ways they are measured, units which they are measured in, and tools used to measure them. Also, remember the different methods for measuring volume.

  30. Warm up % ERROR/METRICS • 1. A lab tech measures the boiling point of water to be 99.5 C. The true boiling pt of water is 100.0 C. Calculate the % error. (SHOW WORK!!) • 2. 0.0075 g = ______________________ng • 3. 3400 kg = ____________________Mg • 4. 258 daL = _______________________mL • 5. 534 L = __________________cm3

  31. 99.5 – 100.0 x 100 = 0.5% 100.0 • 7 500 000 ng • 3.4 Mg • 2 580 000 mL • 534 000 cc (mL)

  32. ACTIVATOR In a paragraph, describe how mass, volume, length, and temperature are measured.

  33. LAB—UNCERTAINTY OF MEASUREMENT PART III #8 SHOW WORK FOR % ERROR Accepted values: Bottle = 7.095 grams Clamp = 75.069 grams Domino = 5.371 grams Stopper = 7.090 grams

  34. METRIC WARMUP • GIVE THE SYMBOL FOR EACH UNIT: • 1. Micrometer 4. Megameter • 2. Meter 5. millimeter • 3. Kiloliter • WHAT QUANTITY DO THESE UNITS MEASURE? • 7. meter 10. gram • 8. cc 11. Cm3 • 9. liter 12. Square meter • PERFORM THESE METRIC CONVERSIONS: • 13. 2.67 ng = _______________pg • 14. 34000 m = ______________Mm • 15. 50 cc =_______________mL • 16. 3 L = __________________cm3

  35. CONVERSIONS INVOLVING EXPONENTS • This is done when BOTH units have the SAME exponent (squared to squared or cubed to cubed) • Ex: 100 cm2 = _______________m2 cm to m is normally 2 spaces left, so multiply this 2 spaces x the exponent of 2 = total of 4 spaces left Ex: 0.0075 Mm3 = ________________km3 Mm to km is normally 3 spaces right, so multiply by exponent of 3 = 9 spaces right

  36. FINAL METRIC WARMUP • 1. 55 cc = ______L • 2. 0.00035 Mm = _________m • 3. 675 dL =____________kL • 4. What do millimeters measure? • 5. What do kilograms measure? • 6. What do liters measure? • 7. What do cubic millimeters measure? • 8. What do square centimeters measure? • 9. Which is larger: 250 cc or 0.5 L? • 10. Find the area of a box measuring 5 cm by 8 cm. • 11. Does millimake the base unit larger or smaller? • 12. Find the volume of a rock that’s dropped in 25 mL of water and the level then rises to 38 mL.

  37. 1. 0.055 L • 2. 350 m • 3. 0.0675 kL • 4. length • 5. mass • 6. volume • 7. volume • 8. area • 9. 0.25 L or 0.5 L • 10. 5 cm x 8 cm = 40 cm2 • 11. smaller • 12. 38 – 25 = 13 mL

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