Significant Figures(1)

# Significant Figures(1) - SIGNIFICANT FIGURES There is some...

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SIGNIFICANT FIGURES There is some uncertainty in every measured quantity. Every reported result should reflect the precision of the measurement. Significant figures are important in lab because they tell us how precisely we know a quantity and how well we can reproduce a laboratory measurement. (The term “accuracy” is used to refer to how closely a value measured in the laboratory is to the “true” value.) Consider two densities, 0.8 g/mL and 0.826 g/mL. The 0.826 g/mL number is more precise. The last digit on the right a lways indicates the “uncertain” or “doubtful” digit because we do not know what the digit directly to its right is. Here are the rules for determining the number of significant figures: a) Nonzero digits are always significant. b) Zeroes may or may not be significant, depending on where they are in the number. (1) zeroes between other nonzero digits are always significant (2) zeroes to the left of the first nonzero digit are never significant (3) zeroes to the right of the last nonzero digit to the right of the decimal point are significant (4) zeroes to the right of the last nonzero digit, not in a decimal, may or may not be significant; use exponential notation for a precise expression of sig. figs. Table 1.

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## This note was uploaded on 10/04/2010 for the course CHEM 145 taught by Professor Prezhdo during the Fall '08 term at University of Washington.

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Significant Figures(1) - SIGNIFICANT FIGURES There is some...

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