Why do we need to know significant figures? We as scientists
need to measure things as we perform experiments. Instruments have
different degrees of precision We measure to the last known
calibration, and estimate the unknown.
Slide 3
Significant = replaceable A number is significant because it
can be replaced by another number in a measurement
Slide 4
The Rules
Slide 5
Significant Figures The Rules 1. Nonzero numbers 1 9 are always
significant. Examples: 1 meter 1 sig fig 92 liters 2 sig figs 34578
grams 5 sig figs
Slide 6
Significant Figures The Rules 2. Imbedded zeros (zeros between
nonzero numbers) are always significant. Examples: 202 cm3 sig figs
10509 mL5 sig figs 2039 kg4 sig figs 90009 g5 sig figs
Slide 7
Significant Figures The Rules 3. Leading zeros are never
significant. 4. Trailing zeros after a nonzero number after the
decimal are significant. Examples: 0.00000540 g3 sig figs 0.3700
mm4 sig figs 0.00101 L3 sig figs
Slide 8
Significant Figures The Rules 5. Trailing zeros before the
decimal are significant only if the decimal point is specified.
Examples: 100. dg3 sig figs 100 dg1 sig fig 8900 km 2 sig figs
8900. km4 sig figs
Slide 9
Exact Numbers An exact number is a number that cannot be
changed. (Cannot be halved or split up) Ex. 2 atoms, 1 proton, a
hundred dollar bill We include most conversion factors as exact
numbers Ex. 1m = 100 cm When you work with exact numbers, you
consider them to have infinite sig figs. (You dont have to worry
about them!)
Slide 10
RECAP #1 Leading Zeros Imbedded Zero 0.00770800 Nonzero numbers
Trailing Zeros after the decimal
Slide 11
6 significant figures
Slide 12
RECAP #2 Leading Zeros Imbedded Zero (none) 22060 Nonzero
numbers Trailing zero with no decimal
Slide 13
4 significant figures
Slide 14
Lets Practice!
Slide 15
56 meters 2 sig figs Rule 1
Slide 16
20 grams 1 sig fig Rule 1, 5
Slide 17
303.0 mL 4 sig figs Rule 1, 2, 4
Slide 18
200 dollars 1 sig fig Rule 1, 5
Slide 19
207 donkeys 3 sig figs Rule 1,2
Slide 20
0.7900 grams 4 sig figs Rule 1,3,4
Slide 21
0.0096070 m 5 sig figs Rule 1,2,3,4
Slide 22
102000 km 3 sig figs Rule 1,2,5
Slide 23
1.10 x 10 2 hm 3 sig figs Rule 1, 4
Slide 24
2.2 x 10 34 atoms 2 sig figs Rule 1
Slide 25
Rounding Numbers If you have to round and the number you are
looking to round is less than 5, dont round. Example: 214 round to
2 s.f. Answer = 210
Slide 26
Rounding Numbers If you have to round and the number you are
looking to round is 5 or greater, round up. Example: 215 round to 2
s.f. Answer = 220