Chemistry Conversions
Dimensional Analysis and the Metric
System of Measurements
SI Prefixes
Prefix
Abbreviation
Exponential
Multiplier
Meaning
Example using length
Kilo-
k
103
1000
1 kilometer (km) = 1000
m
Hecto-
h
102
100
1 hectometer (hm) = 100
m
Deka-
da
101
10
1 dekameter (dam) = 10
m
100
1
1 meter (m)
Deci-
d
10-1
1/10
1 decimeter (dm) = 0.1
m
Centi-
c
10-2
1/100
1 centimeter (cm) = 0.01
m
Milli-
m
10-3
1/1000
1 millimeter (mm) =
0.001 m
Converting From One Unit to Another
• We will convert A LOT!
• Uses a technique called Factor Label Method
• Cancels out units and does the math for you!!
Factor-Label Method for Conversions
• Mathematics used Numbers, rather than Quantities
• Chemistry uses these same Numbers along with the
value’s Units
• A Number is useless without its unit
• Units give the Number an actual meaning
Conversion Factors
• A conversion Factor is needed to go from one unit
to another
• You must first know how much of one thing is of
another before making any conversions
• We all know 1 foot is made up of 12 inches
SO…
• The conversion factor needed to go from feet
to inches or from inches to feet is
1 foot / 12 inches
or
12 inches / 1 foot,
Some Conversion Factors
1 mile = 1.61 Kilometers
1 inch = 2.54 centimeters
1 gallon = 3.71 Liters
• Lets Convert:
157 lbs to kilograms
Conversion Factor We May Want To Know:
1 pound = 0.454 Kilograms
Conversions
1 pound = 0.454 Kg
157 lb
0.454 kg
1 lb
The “Heart” of the problem
is where the conversion
actually takes place. This is
where your conversion factor
does its work.
Conversions
1 pound = 0.454 Kg
157 lb
0.454 kg
1 lb
( 157 * 0.454 ) / 1 = 71.27
= 71.3 kg
So yes, with the proper units 157 lb does equal 71.3 kg, but without
units the values are not the same, as we do not know the correct
representation numbers.
Units
• Units are everything. They give any value an actual
meaning and interpretation.
• Always carry your units through, rewriting them
until you reach a final value, or you will be lost.
Converting with English Units
Question:
Convert 15.41 yards to inches:
Conversion Factors:
• 1 yard = 3 feet
• 1 foot = 12 inches
Converting with Metric Units
Convert 15.41 yards to inches:
15.41 yd
Conversion Factors:
• 1 yard = 3 feet
• 1 foot = 12 inches
Converting with Metric Units
Convert 15.41 yards to inches:
15.41 yd
3 ft
1 yd
Conversion Factors:
• 1 yard = 3 feet
• 1 foot = 12 inches
Converting with Metric Units
Convert 15.41 yards to inches:
15.41 yd
3 ft
1 yd
Conversion Factors:
• 1 yard = 3 feet
• 1 foot = 12 inches
12 in.
1 ft
Converting with Metric Units
Convert 15.41 yards to inches:
15.41 yd
3 ft
1 yd
12 in.
1 ft
= (15.41 * 3 * 12) / 1
15.41 yards = 554.8 inches
Metric System
Common Metric Prefixes:
Prefix
Abbreviation
Value (Base Unit)
Kilometer
km
1000
Hectometer
hm
100
Dekameter
dam
10
Base Unit (meter)
meter
1
Centimeter
cm
0.01
Millimeter
mm
0.001
Micrometer
µm
0.000001
Converting with Metric Units
Question:
Convert 0.248 km to centimeters:
Conversion Factors:
• 1 Kilometer = 1000 meters
• 1 meter = 100 centimeters
Prefix
Abbreviation
Value (Base Unit)
Kilometer
km
1000
Hectometer
hm
100
Dekameter
dam
10
Base Unit (meter)
meter
1
Centimeter
cm
0.01
Millimeter
mm
0.001
Micrometer
µm
0.000001
Converting with Metric Units
Covert 0.248 km to centimeters:
0.248 km
Conversion Factors:
• 1 Kilometer = 1000 meters
• 1 meter = 100 centimeters
Converting with Metric Units
Covert 0.248 km to centimeters:
0.248 km
1000 m
1 km
Conversion Factors:
• 1 Kilometer = 1000 meters
• 1 meter = 100 centimeters
Converting with Metric Units
Convert 0.248 km to centimeters:
0.248 km
1000 m
1 km
100 cm
1m
Conversion Factors:
• 1 Kilometer = 1000 meters
• 1 meter = 100 centimeters
Converting with Metric Units
Convert 0.248 km to centimeters:
0.248 km
1000 m
1 km
100 cm
1m
= (0.248 * 1000 * 100) / 1
= 24,800 centimeters
Much Easier!
Calculations: Metric Vs. American
System?
Prefix
Abbreviation
Value (Base Unit)
Kilometer
km
1000
Hectometer
hm
100
Dekameter
dam
10
Base Unit (meter)
meter
1
Centimeter
cm
0.01
Millimeter
mm
0.001
Micrometer
µm
0.000001
Just count the zeros and move the decimal
spot to the left or the right.