1. Factor Label
Chemistry Chapter 10

2. Base SI Units Quantity Base Unit Symbol Length Meter m Mass kilogramkg
Time
second s
Temperature
kelvin K
Amount of substance
Mole
mol

3. SI Prefixes Prefix Factor Abbr Ratio example mega 106 or 1,000,000 M
1Mg = 1x106 g
kilo
103 or 1,000 K
1Kg = 1000 g
deka 10 da
1 dag = 10 g
suffix or base = 1
meter, liter, gram
deci
or .1 d
1 g = 10 dg
centi
or .01 c
1 g = 100 cg
milli
or .001 m
1 g = 1000 mg
micro
10-6
1 g = 1x106 µg
nano
10-9 n
1 g = 1x109 ng

4. Factor-Label Method or Dimensional Analysis
The factor-label method was developed to:
Can change one set of units to another
Equalities (i.e., conversion factors) are set up in fraction form
Equalities lined up sequentially and units used on the top and bottom of neighboring fractions are alternated so that units cancel
Three steps to problems:
Step 1: State the given quantity (number and units) and unknown
Step 2: Indicate Ratio(s)
Step 3: Start with what you know

5. Example Factor Label problem
How many centimeters are in 5.00 inches?
Step 1: in = ? cm
Step 2: Indicate Ratio
1.00 in = 2.54 cm
(1.00 in) or (2.54 cm)
(2.54 cm) (1.00 in)
Step 3: Start with what you know
Must cancel units
Must show units
Box answer
(5.00 in) (2.54 cm) = 12.7 cm
(1.00 in)

6. Factor Label Examples ( ( ( ( ( ( = = 3000000 cm = ? Km 1 m = 100 cm
25 cm2 = ? m2
1 m = 100 cm 1m
100 cm ( 1m
100 cm (
25 cm2 1 ( =
.0025 m2

7. Factor Label Example ( ( ( ( = 55.0 km/hr = ? m/s 1 km = 1000m
1 hr = 60 min
1 min = 60 sec
1 min
60 sec (
55.0 km
1 hr (
1000 m
1 km (
1 hr
60 min ( =
15.3 m/sec