Unit ConversionsFactor Label Method

Factor Label Method

• Measurements that are made of some aspect of the universe must have a quantity and a unit.

• Many times, values are not measured in the unit that we want.

• We have to do some math to get the numbers in the form that we desire.

Dimensional AnalysisFactor Label Method

• To convert a measurement from one unit to another, multiply the known quantity and unit(s) by a conversion factor

Quantity with

xConversion

=

Quantity with

WrongUnit

Factor DesiredUnit

Conversion Factors• Conversion Factors come from equalities• Equalities yield two conversion factors:

1 ft = 12 in

OR 112

1

in

ft

Factor Label Method ExampleConvert 179,800 s to minutes•Think of the relationship(s) between the unit you are given and the desired unit.

1 min = 60 secFrom this equality, we get two conversion factors: OR

(SF) min2997When determining the amount of significant figures for our answer, we only look at measurements given by the problem. We never consider conversion factors when determining the amount of significant figures for our answer!

Kilo-

Hecto-

Deka-

Base Unit

Deci-

Centi-

Milli-

gramsliters

meters

1 kg = 1000 g

1 hg = 100 g

1 dkg = 10 g

1 g = 10 dg

1 g = 100 cg

1 g = 1000 mg

Metric Conversions