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Significant Figures. Significant Figures. Significant Figures Notes – Physical Science 1. Significant figures apply to measured values. They are significant to the measurement NOT to the number.
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Significant Figures • Significant Figures Notes – Physical Science • 1. Significant figures apply to measured values. They are significant to the measurement NOT to the number. • 2. The number of significant figures is determined by the resolution of the instrument used to make the measurement. • The last digit in a measured number is always the “estimated” digit.
Rules for Counting Significant Figures • Non-zero numbers are ALWAYS significant. Example: 312cm and 0.546mm both have ______ significant figures 3
Sig. Fig. Rules - continued • Leading Zeros are NEVER significant. Example: 0.000047pm has _____ significant figures. consider this number in scientific notation: 4.7 x 10-5 How many significant figures? 2
Sig. Fig. Rules - continued • Captured Zeros, zeros between two non zero numbers, are ALWAYS significant. Example: Both 4,005km and 40.05dm contain ______ significant figures. 4
Sig. Fig. Rules - continued • Trailing Zeros are only significant if they are present with a decimal place. Example: 120mL has _____ sig. figs. 120.0mL has _____ sig. figs. Which number was measured with the more accurate volumetric measuring device? 2 4
Sig. Fig. Rules - continued • Significant figures DO NOT APPLY to “counted” or “exact” numbers or definitions. Examples: 1 inch = 2.54 cm has NO sig. Fig. 14 pencils has NO sig figs. You do not use these numbers to determine the number of sig figs in your answer
Significant Figures Rules Summary • Non-zero numbers – Always Significant • Captured zeros – Always Significant • Leading zeros – Never Significant • Trailing zeros – Only with a decimal • Counted numbers – does not apply • Numeric Definitions – does not apply
Rounding Rules • Rule 1 - if the remainder beyond the last digit to be reported is less than 5, drop the numbers past the last digit. Example: Rounding to one decimal place, the number 5.3467 becomes 5.3. • Rule 2 - if the remainder is equal or greater than 5, increase the final digit by 1. Example: The number 5.798 becomes 5.8 if rounding to 2 digits. 4.025 becomes 4.03 if rounding to 3 digits.
Multiplying/Dividing with Significant Figures: • The answer will have the same number of sig figs as the number with the least sig. figs in the calculation. • Example: 30 x 5.1 = _______ BUT: 30 has only ____ sig fig so the answer can only have _____ sig fig. The correct answer is _____ 153 1 1 200
Adding/Subtracting with Significant Figures • The answer will have the same number of decimal places as the number with the least decimal places in the calculation. Example: 331.34 + 3.2 = ___________ BUT 3.2 has only one decimal place so the rounded answer is ______ 334.54 334.5
Practice – How many significant figures? None • 46 marbles • 3.02 x 102 cm • 0.003407 in. • 230 mL • 2.4cm x 3.21cm • 5.66mL + 1.234mL • 6.02 x 1023 atoms 3 4 2 2 3 None