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Factor Label
Chemistry Chapter 10
Base SI Units
Quantity
Length
Base Unit
Meter
Mass
kilogram
kg
Time
second
s
Temperature kelvin
Amount of
substance
Mole
Symbol
m
K
mol
SI Prefixes
Prefix Factor
mega 106 or 1,000,000
Abbr Ratio example
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
10-1 or .1
d
1 g = 10 dg
centi
10-2 or .01
c
1 g = 100 cg
milli
10-3 or .001
m
1 g = 1000 mg
micro
10-6
µ
1 g = 1x106 µg
nano
10-9
n
1 g = 1x109 ng
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
Example Factor Label problem
How many centimeters are in 5.00 inches?

Step 1: 5.00 in = ? cm

Step 2: Indicate Ratio
1.00 in = 2.54 cm
(1.00 in)
(2.54 cm)

or
(2.54 cm)
(1.00 in)
Step 3: Start with what you know
(5.00 in) (2.54 cm) = 12.7 cm
1
(1.00 in)
Must cancel units
Must show units
Box answer
Factor Label Examples
3000000 cm = ? Km
1 m = 100 cm
1 km = 1000m
(
1
(
(
(
1m
100 cm
1 km
( 1000 m
(
3000000 cm
=
30 km
25 cm2 = ? m2
1 m = 100 cm
(
(
1
( 1001mcm
( 1001mcm
(
(
25 cm2
=
.0025 m2
Factor Label Example
55.0 km/hr = ? m/s
1 km = 1000m
1 hr = 60 min
1 min = 60 sec
(
1 km
(
1 hr
60 min
(
(
1 hr
(
1000 m
(
1 min
60 sec
(
(
55.0 km
=
15.3 m/sec