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 precise.

•How accurate is a:•Meterstick•Electronic balance•Graduated cylinder

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

Significant Figure Rules

1) All non-zero digits and zeros between non-zero digits are significant.

22.754007

2) Leading zeros are not significant.

0.750.000033

7

3)Zeros to the right of all non zero digits are only significant if the decimal point is shown (or if a bar is placed over the zero).780

27.000.0300

4) For values written in scientific notation, the digits in the coefficient are significant.

6.02x1023

3.00x10-6

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

•When multiplying or dividing using significant figures, the product or quotient will contain the same number of significant figures as the number with the least significant figures.What is 23.95 x 11.7?

Adding/Subtracting with Sig Figs

•When adding or subtracting with significant figures, the sum or difference has the same number of decimal places as the measurement with the least number 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