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Measurement

Measurement. Accuracy & Precision. Accuracy. How close a measurement is to the actual value. Precision. How close a series of measurements are to each other. Significant figures. We get sig figs from the idea that we can only be a precise as our least precise measurement.

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Measurement

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  1. Measurement Accuracy & Precision

  2. Accuracy • How close a measurement is to the actual value

  3. Precision How close a series of measurements are to each other

  4. Significant figures • We get sig figs from the idea that we can only be a precise as our least precise measurement. • Basically, sig figs tell us how Exact our numbers are!

  5. Rules for identifying sig figs Ex) 23.45 (4 SF’s) Ex) 2002 (4 SF’s) Ex) 12.002 (5 SF’s) Ex) 1200 (2 sig figs) • All NON-zero digits are significant • All zeros between 2 non-zero digits are significant • Zeroes to left of understood decimal point are NOT SIGNIFICANT!

  6. Sig figs (cont) • 200. (3 SF’s) • 12320. (5 SF’s) • 0.00045 (2 SF’s) • 0.01 (1 SF) 4. All zeros to the left of a expressed decimal point are significant if number is greater than 1 5. All zeros to right of a decimal point, but left of non-zero digit are NOT SIGNIFICANT! (if number is less than 1)

  7. Sig figs (cont) • 0.0300 (3 SF’s) • 0.02000 (4 SF’s) 6. All zeros to right of decimal and right of non zero digit are significant

  8. Sig figs (cont) Ex) 5.334 X 103 (4 SF’s) Ex) 3.00 X 10-5 (3 SF’s) 7. All digits expressed in front of power of 10 in Scientific Notation are significant.

  9. Identifying Practice • 5.550 g • 100 hs • 3450 dg • 0.000023404 cg • 7.650 mm • 400. L • 230.00 das • 3.45 X 1012 kg • 9.240 X 10-2 cs 4 1 3 5 4 3 5 3 4

  10. Identifying Extra Practice • 7.00 • 0.001 • 400 • 21004004 • .00340 • 4.56 X 104 • 1200. • 2300.01 3 1 1 8 3 3 4 6

  11. Rounding For each of the following numbers, round to 3 sig figs • 1.5587 m • .0037421 cm • 1367 dg • 128,522 kL • 1.6683 106 mm 1.56 m .00374 cm 1370 dg 129000 kL 1.67 X 106 mm

  12. Rounding Extra Practice • 4500 cs (1) • 39020 dg (3) • 0.004530 mm (2) • 0.000897 kg (2) • 450.0069 g (5) • 12890 hg (2) • 0.00045682 ms (1) • 129.95 kL (4) 5000 cs 39000 dg 0.0045 mm 0.00090 kg 450.01 g 13000 hg 0.0005 ms 130.0 kL

  13. S.F. Multiplication/Division • Ex:) 5.33 X 1.2 = 6.396 * Answer can only have 2 S.F.’s, so the answer must be rounded to 6.4 • Answer can only have the same quantity of sig figs as the least significant number used in the calculation

  14. Multiplication/Division Practice Complete the following: • 38 g  22.4 g • 48.3 mm / 12.0 mm • 3.47 cm / 40 cm • 428.3 mL  2.4 mL 850 g 4.03 mm 0.09 cm 1000 mL

  15. Addition & Subtraction 2 D.P. FOCUS ON DECIMAL PLACES!! The answer can only have the same number of decimal places as the number used to obtain it with the fewest decimal places • 35.09 + 0.2350 35.3250 (Answer can only have 2 D.P) In sig figs= 35.33 4 D.P.

  16. Problems • 22.3 cm + 3.45 cm • 7.2 s + 15 s • 6.0 kg – 5.34 kg • 48 m – 0.0025 m 25.8 cm 22 s 0.7 kg 48 m

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