The Foundations of Chemistry

the United States, all units of measure are set by the National Institute of Standards and
Technology, NIST (formerly the National Bureau of Standards, NBS). Measurements in
the scientific world are usually expressed in the units of the metric system or its mod-
ernized successor, the International System of Units (SI). The SI, adopted by the National
Bureau of Standards in 1964, is based on the seven fundamental units listed in Table 1-4.
All other units of measurement are derived from them.
In this text we shall use both metric units and SI units. Conversions between non-SI
and SI units are usually straightforward. Appendix C lists some important units of
measurement and their relationships to one another. Appendix D lists several useful
physical constants. The most frequently used of these appear on the inside back
cover.
The metric and SI systems are decimal systems, in which prefixes are used to indicate frac-
tions and multiples of ten.The same prefixes are used with all units of measurement. The
distances and masses in Table 1-5 illustrate the use of some common prefixes and the
relationships among them.

The abbreviation SI comes from the

French le Système International.

1-6 Measurements in Chemistry 17

The prefixes used in the SI and

metric systems may be thought of as

multipliers. For example, the prefix kilo-

indicates multiplication by 1000 or

103 , and milli- indicates multiplication

by 0.001 or 10^3.

TABLE 1-4 The Seven Fundamental

Units of Measurement (SI)

Physical Property Name of Unit Symbol

length meter m

mass kilogram kg

time second s

electric current ampere A

temperature kelvin K

luminous intensity candela cd

amount of substance mole mol

TABLE 1-5 Common Prefixes Used in the SI and Metric Systems

Prefix Abbreviation Meaning Example

mega- M 106 1 megameter (Mm)
1  106 m

kilo-* k 103 1 kilometer (km)
1  103 m

deci- d 10 ^1 1 decimeter (dm)
1  10 ^1 m

centi-* c 10 ^2 1 centimeter (cm)
1  10 ^2 m

milli-* m 10 ^3 1 milligram (mg)
1  10 ^3 g

micro-* † 10 ^6 1 microgram (g)
1  10 ^6 g

nano-* n 10 ^9 1 nanogram (ng)
1  10 ^9 g

pico- p 10 ^12 1 picogram (pg)
1  10 ^12 g

*These prefixes are commonly used in chemistry.
†This is the Greek letter (pronounced “mew”).

See the Saunders Interactive

General Chemistry CD-ROM,

Screen 1.16, The Metric System.