Comments?
What do they do if someone moves in?
If you counted everyone in Pekin, would you come up with 33,900
Significant Figures or “Sig Figs”
Whose more important, me or you?
1 0
Significant Figures or “Sig Figs”
DO NOT mean a number is important or not
DOES indicate the precision of a number
Odometer on your car
The 1st calculation of the
Everest’s
height was done in 1852 by
Radhanath Sikdar
He calculated
He reported
--> 29,000 ft
--> 29,002 ft. WHY?
Latest Measurement is 29,028 ft.
See Sig Fig cards
Look at the examples and come up with 3
rules for when a number is significant or not
1.) Any number 1-9 is always significant
2.)
3.)
4.)
Come up with 3 more on a piece of paper with your
groups name on it to turn in
The Rules
1.) Non-zero numbers are always significant
1, 2, 3, 4, 5, 6, 7, 8, 9
and so is a zero with a line over it (it does not mean repeating in
this class)
Examples
12 ft
2 sig figs
.4512 cL
4 sig figs
32.2 mm
3 sig figs
140 ms
3 sig figs
The Rules
2.) 0’s between Sig Figs are always
significant.
Examples
302 s
3 sig figs
4.0552 kL
5 sig figs
300.2 cm3
4 sig figs
1,000,000,001 mg
50500 mg
10 sig figs
5 sig figs
The Rules
3.) 0’s to the left of all non-zero numbers
are never significant
These zeros don’t
mean anything
Examples
0035 mi
2 sig figs
.000898 g
3 sig figs
00.000003 L 1 sig figs
These zeros are
just place holders
The Rules
4.) 0’s to the right of all non-zero numbers are
only significant if they are to the right of a
decimal. ( or if they are between 2 sig figs)
Examples
These zeros are
just placeholders
35,000 in
2 sig figs
0.050 kg
2 sig figs
600.000 s
6 sig figs
780.0 cm
4 sig figs
The Rules
5.) Measurements done by counting have infinite Sig Figs
(Infinite Precision). So do numbers that are considered perfect by
definition.
Examples
counted
By
definition
4 apples
Number of people in the class room
12 inches = 1 foot
water freezes at 0oC
1 inch = 2.54 cm
HOW MANY SIG FIGS
120 mm
6306 g
.008909 L
1.0050 dm
HOW MANY SIG FIGS
00.005000 cs
360,000 mL
890.00 kg
10000 ms
The Guess #
is the furthest SIG FIG to the right
654 ft
.005 s
8,500 s
40.00 s
Find the Guess
120 mm
6306 g
.008909 L
1.0050 dm
HOW MANY SIG FIGS
00.005000 cs
360,000 mL
890.00 kg
10000 ms
The easy stuff - Sig Figs with scientific notation
exponent
2.4 x105
base
coefficient
All numbers in the coefficient are significant. Ignore everything else
2.4 x105
5 x109
2 Sig Figs
1 Sig Figs
1.00005 x101
6 Sig Figs
Rounding to # of Sig Figs
Find the left most SIG FIG. (biggest 10’s place)
Count to the right the number of sig figs to keep.
If the number to the right is 0-4 round “down”
If the number to the right is 5- 9 round up
Round the following
52.38
49.56
round to 3 SFs
round to 2 SFs
round to 1 SF
round to 3 SF
round to 2 SF
round to 1 SF
Round the following
.00070008
50095
round to 4 SFs
round to 3 SFs
round to 2 SFs
round to 1 SFs
round to 4 SFs
round to 3 SFs
round to 2 SFs
round to 1 SFs