Transcript Significant Figures -why we use them -rules for 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?
Captive zeros
2) All zeros that are between
two non-zero digits are
significant.
How many significant figures
are in the number 28,005?
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
-6
2.00x10
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
21
1.5x10
x
13
2.07x10
6
19
1.8x10 /2.77x10
Rounding
• 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?