David Healy 2010
Unit Conversion and Dimensional Analysis
Frequently in Chemistry you will be provided with data describing a particular quantity in a
certain unit of measurement, and you will be required to convert it to a different unit which
measures the same quantity. This process is frequently described as Unit Conversion. As an
example, you may be given a measurement of length in centimeters which must be converted to
meters. This worksheet includes the rules and some guidelines to help you with converting,
density problems, stoichiometry problems, and concentration problems. This worksheet is not
intended to help you with reading comprehension of word problems regarding these types of
questions, just the mathematical application.
Rules
1.) Identify the given measurement.
2.) Identify the unit that the measurement must be converted to.
3.) Use conversion factors (relationship between two units) that link your given unit to your
final unit.
4.) Perform the mathematical calculations.
5.) Do not forget to apply significant figures to your final answer.
Guidelines
1.) When converting a single unit, such as converting from centimeters to meters, the given
should also be a single unit as well. It can become more difficult by starting with the
conversion factor: (100 cm / 1 m). Even if you know a dozen = 12, the relationship
cannot be applied if you do not know how many dozen you care about.
2.) When only a single unit given, it should be written over 1. For example, 56.93 cm should
be written as 56.93 cm / 1. Units lacking a number are assumed to be 1. If we were given
1.193 g / ml, we would write this as 1.193 g / 1 ml .
3.) Any relationship between two units can potentially be utilized as a conversion factor:
density relates mass and volume while molar mass relates moles and mass. Express these
conversion factors as a fraction in the dimensional analysis.
4.) A conversion factor can be written in two different ways. For example, converting
centimeters and meters, we can use the conversion factor (100 cm / 1 m) or (1 m / 100
cm). The unit you want to remove from the problem should be placed opposite of the
original. So, to convert from cm to m, cm is your given unit, and the cm should be in the
bottom to denominator out cm from the problem.