-why we use them -rules for sig. figs. -operations with sig. figs Significant Figures                                                                                                                                              -why we use them -rules for sig. figs. -operations with sig. figs

What are Significant Figures? They are all the numbers in a measurement that are known with certainty plus the first digit that is uncertain.

Why use Significant Figures? Significant figures are needed in science, because the tools we use to measure are not infinitely accurate. How accurate is a: Meter stick Electronic balance Graduated cylinder

SIDENOTE: You will hear significant figures also called: Significant digits Sig figs

Significant Figure Rules 1) All non-zero digits are significant. How many significant figures are in the number 29.589?

2) All zeros that are between two non-zero digits are significant. Captive zeros 2) All zeros that are between two non-zero digits are significant. How many significant figures are in the number 28,005?

3) Zeros to the right of a non-zero count only if there is a decimal . Trailing Zeros 3) Zeros to the right of a non-zero count only if there is a decimal . How many significant figures are in the number 23,000? How many significant figures are in the number 80.0?

Leading Zeros 4) All zeros in front of non-zero digits are NOT significant (includes to the right and left of the decimal) How many significant figures are in the number 0.00025?

How many SIGNIFICANT FIGURES are in the following numbers?

83.591

5007

10.005

20 080

1 000 000

0.0012

1.007

196.0

75000.

1.52x10 22

2.00x10-6

Multiplying/Dividing with Sig Figs Answer should have the same # sig figs as the quantity with the least # of sig figs. What is 23.95 x 11.7?

Adding/Subtracting with Sig Figs Answer should have the same # of decimal places as the quantity with the least # of decimal places. What is 23.95 + 11.7?

Do the following problems with the correct number of SIGNIFICANT FIGURES.

24 x 31.8

8.4/4.2

49.1 – 8.001

81.350 + 7.35

0.0056 x 3.227

1007/33.6

20300 – 2878.6

1.005 – 3.60

76.00 x 13

1.5x1021 x 2.07x1013

1.8x106/2.77x1019

Rounding What is 44.4? What is 67.5? If the last decimal is below 5, round down If the last digit is 5 or above, round up What is 44.4? What is 67.5?