Chemistry I

Precision and Accuracy Accuracy refers to the agreement of a particular value with the true value. Precision refers to the degree of agreement among several measurements made in the same manner. Neither accurate nor precise Precise but not accurate Precise and accurate

Rules for Counting Significant Figures Nonzero integers- Every nonzero digit in a reported measurement is assumed to be significant has 4 significant figures

Rules for Counting Significant Figures Zeros Leading zeros do not count as significant figures. They act as placeholders. By writing the measurements in scientific notation, you can eliminate such place holding zeros has 3 significant figures has 2 significant figures

Rules for Counting Significant Figures Zeros Sandwiched zeros : ( zeros appearing between nonzero digits) always count as significant figures has 4 significant figures 7003 has 4 significant figures

Rules for Counting Significant Figures Zeros Trailing zeros are significant only if the number contains a decimal point. 300 meters has 1 significant figure 7000 has 1 significant figure 27,210 has Four significant figures

Zeros at the end of a number and to the right of a decimal point are always significant has Four significant figures has 4 significant figures has 4 significant figures 9000 has 1 significant figure

Sig fig Practice # 1 How many significant figures in each of the following? m ----  5 sig figs kg  4 sig figs 100,890 L --  5 sig figs 3.29 x 10^3 s --  3 sig figs cm --  2 sig figs 3,200,000  2 sig figs

Rules for significant figures in mathematical operations Multiplication and Division – Answer has the same number of significant figures as the least sig fig number in the question. Ex x 2.0 =  13 (2 significant figures)

Rules for significant figures in mathematical operations Addition and Subtraction: The answer has to be rounded to the same number of decimal places as the measurement with the least number of decimal places in the question. Ex: =  18.7 ( 3 sig figs)