Measurement: Significant Figures

Significant Figures  Significant Figures (sig. figs.): the number of digits that carry meaning contributing to the precision of a measurement or calculated data.

Precision and Accuracy Low Accuracy High Precision High Accuracy Low Precision High Accuracy High Precision

Significant Figures  Significant figures, which are also called significant digits, are very important in science.  Each recorded measurement has a certain number of significant figures.  Calculations done on these measurements must follow the rules for significant figures.

Significant Figures  The significance of a digit has to do with whether it represents a true measurement or not.  Any digit that is actually measured or estimated will be considered significant.  Placeholders, or digits that have not been measured or estimated, are not considered significant.

Significant Figures  There are 5 rules to determine which zeros in a number are significant or not.

Rules for Significant Figures  Rule #1: All non-zero digits (1-9) are significant. For example: 453 number of sig figs______ number of sig figs______

Rules for Significant Figures  Rule #2: Zeros between non-zero digits are significant. For example: number of sig figs______ number of sig figs______

Rules for Significant Figures  Rule #3: Zeros to the left (“leading” zeros) of the first non-zero digit are NOT significant. For example: 1.02 number of sig figs______ 0.12 number of sig figs______ number of sig figs______ number of sig figs______

Rules for Significant Figures  Rule #4: If a number ends in zeros (“lagging” zeros) to the right of the decimal point, those zeros are significant. For example:  2number of sig figs______ 2.0 number of sig figs______ 2.00number of sig figs______ number of sig figs______ {This signifies greater precision.}

Rules for Significant Figures  Rule #5: If a number ends in zeros (“lagging” zeros), the zeros to the right are NOT significant IF there is NO decimal point present. For example: number of sig figs______ 20060number of sig figs______ 40000number of sig figs______

Sig. Figs. Practice Ex 1) Ex 2) ) ) ) ) ) ) ) ) Ex 1) (5 sig. figs.) Ex 2) (4 sig. figs) 1) (5 sig. figs.) 2) (4 sig. figs.) 3) (4 sig. figs.) 4) (5 sig. figs.) 5) (2 sig. figs.) 6) (5 sig. figs.) 7) (7 sig. figs.) 8) (6 sig. figs.)