Transcript Significant Figures (sig. figs)

Significant Figures (sig. figs)
Rules:
 All non-zero #’s are significant
 Some zeros are significant; others are
place holders

Sig Figs
Only measurements have sig figs.
 Counted numbers are exact
 A dozen is exactly 12
 A a piece of paper is measured 11 inches
tall.
 Being able to locate, and count significant
figures is an important skill.

Atlantic-Pacific Rule
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Ask yourself: self, is there a decimal?
PACIFIC
(Present)
ATLANTIC
(Absent)
Start from LEFT
& count all #’s from
from
first nonzero
Start from RIGHT
& count all #’s
first nonzero
Practice Makes Perfect!
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How many sig figs?
PRESENT
Start from LEFT and count all #’s
from first nonzero
4.001
 0.0203
 100.

4
3
3
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ABSENT
Start from RIGHT and count all
#’s from first nonzero
4001
 503000
 100

4
3
1
Sig. Figs in Scientific Notation

All #’s (excluding x 10xx) ARE significant
How many sig. figs?:
 3.2 x 103
 3.20 x 103

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Put 0.08400 in scientific notation w/ sig. figs
Sig. Fig. Calculations
Multiplication/Division
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
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Rules:
The measurement w/ the smallest # of sig. figs
determines the # of sig. figs in answer
Let’s Practice!!!
6.221cm x 5.2cm = 32.3492 cm2
4
2
How many sig figs in final answer???
And the answer is….
32 cm2
Adding and subtracting with sig
figs
The last sig fig in a measurement is an
estimate.
 Your answer when you add or subtract can
not be better than your worst estimate.
 have to round it to the least place of the
measurement in the problem

For example
27.93 + 6.4

+
First line up the decimal places
Then do the adding
27.93
Find the estimated
6.4
numbers in the problem
34.33 This answer must be
rounded to the tenths place
Rounding rules

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look at the number behind the one you’re
rounding.
If it is 0 to 4 don’t change it
If it is 5 to 9 make it one bigger
round 45.462 to four sig figs
to three sig figs
to two sig figs
to one sig fig
I.
Significant Figures
How many significant figures does each of
the following numbers contain.
7
6
2. 9,999.900
____________
2
4. 4.7 x 10-3
____________
2
6. 84.007
1. 6.03001
____________
3. 0.00092
___________
5. 9.1 x 108
___________
4
7. 3.206
____________
9. 4.20
____________
3
8. 3.8 x 10-5
10. 42,300
2
5
____________
2
3
____________
____________
II.
Round off the following to three significant figures.
11. 0.01025
____________
12. 0.00543
____________
13. 7.013
____________
15. 0.03426
____________
16. 234.78
____________
17. 124,530
____________
III. Perform the following operations and express the result to 3 significant figures.
18. 50.05 x 2042 =
______________________
19. 9150 / 6375
=
______________________
20. 3.02 x 0.022 =
______________________
21. 0.076 / 1.23
______________________
=
22. 0.375 + 1.26 + 48.0 =
______________________
23. 8.5 - 0.62 + 0.7805 + 210.8 =
______________________
24. 2972 - 0.262 + 246 + 2.46 =
______________________