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Significant Figures. Calculations. Significant Figure Rules. Non-zero digits are always significant. Zeros between two numbers are significant. Zeros to the left of the number are never significant Zeros to the right of a number are only significant if there is a decimal point. Questions
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Significant Figures Calculations
Significant Figure Rules • Non-zero digits are always significant. • Zeros between two numbers are significant. • Zeros to the left of the number are never significant • Zeros to the right of a number are only significant if there is a decimal point.
Questions A. 20 kg B. 0.0051 g C. 11 m D. 0.010 s E. 90.4 degrees Celsius F. 0.004 cm G. 0.089 kg H. 0.009 00 L I. 100.0 degrees Celsius J. 20 cars How Many Sig Figs? • Answers • A. 1 • B. 2 • C. 2 • D. 2 • E. 3 • F. 1 • G. 2 • H. 3 • I. 4 • J. infinite
Rounding Round 389.60 to: • 4 sig figs: • 389.6 • 3 sig figs • 390. • 2 sig figs • 390 • 1 sig fig • 400
Multiplying and Dividing • Your final answer only may contain as many sig figs as the least accurate measurement. • 0.08685 m x 28.000 m = 2431.8 m2 4 SF 5 SF need 4 sig fig = 2431.8 m2 = 2432 m2
Practice • 0.0036000 cm3 x 10.74 g/cm3 = 0.038664g 5 SF 4 SF 4 SF needed = 0.038664g = 0.03866g • 0.6717 g / 3.99 cm3 = 0.168345 g/cm3 4 SF 3 SF 3 SF needed = 0.168345 g/cm3 = 0.168 g/cm3
Adding and Subtracting • Your final answers only may contain as many decimal places (dp) as the least accurate measurement. • 7.761 g + 65.30 g + 8.000 g = 81.0619 g 3 dp 2 dp 3 dp 2 dp needed = 81.0619 g = 81.06 g
Practice • 69.705 m – 62 m = 7.705 m 3 dp 0 dp 0 dp needed = 7.705 m = 8 m • 50.0 ml + 0.385 ml = 50.385 ml 1 dp 3 dp 1 dp needed = 50.385 ml = 50.4 ml
Tricky • 6 cm x 2 cm = 12 cm2 1 SF 1 SF 1 SF needed = 12 cm2 = 10 cm2 • 24 g / 12 g = 2 g 2 SF 2 SF 2 SF needed = 2.0 g
Tricky – no decimal • 120 ml – 6 ml = 114 ml tens ones tens place needed = 114 ml = 110 ml • 7865 mg + 32 mg + 900 mg = 8797 mg ones ones hundreds hundreds needed = 8797 mg = 8800 mg