2.2: Measurement Systems
Lesson Objectives
The student will:
 state an advantage of using the metric system over the United States customary system.
 state the different prefixes used in the metric system.
Vocabulary
 base unit
 metric system
Introduction
Even in ancient times, humans needed measurement systems for commerce. Land ownership required measurements of length, and the sale of food and other commodities required measurements of mass. The first elementary efforts in measurement required convenient objects to be used as standards, such as the human body. Inch and foot are examples of measurement units that are based on parts of the human body. The inch is based on the width of a man’s thumb, and the foot speaks for itself. The grain is a unit of mass measurement that is based upon the mass of a single grain of wheat. Because grains of wheat are fairly consistent in mass, the quantity of meat purchased could be balanced against some number of grains of wheat on a merchant’s balance.
It should be apparent that measuring the foot of two different people would lead to different results. One way to achieve greater consistency was for everyone to use the foot of one person, such as the king, as the standard. The length of the king’s foot could be marked on pieces of wood, and everyone who needed to measure length could have a copy. Of course, this standard would change when a new king was crowned.
What were needed were objects that could be safely stored without changing over time to serve as standards of measurement. Copies of these objects could then be made and distributed so that everyone was using the exact same units of measure. This was especially important when the requirements of science necessitated accurate, reproducible measurements.
The Metric System
The metric system is an international decimalbased system of measurement. Because the metric system is a decimal system, making conversions between different units of the metric system are always done with factors of ten. To understand why this makes the metric system so useful and easy to manipulate, let’s consider the United States customary system – that is, the measurement system commonly used in the US. For instance, if you need to know how many inches are in a foot, you need to remember:
Metric Prefixes and Equivalents
The metric system uses a number of prefixes along with the base units. A base unit is one that cannot be expressed in terms of other units. The base unit of mass is the gram (g), that of length is the meter (m), and that of volume is the liter (L). Each base unit can be combined with different prefixes to define smaller and larger quantities. When the prefix “centi” is placed in front of gram, as in centigram, the unit is now
Prefix  Meaning  Symbol 

pico 

p 
nano 

n 
micro 


milli 

m 
centi 

c 
deci 

d 
kilo 

k 
Common metric units, their symbols, and their relationships to a base unit are shown below:



1.00 picogram1.00 nanosecond1.00 micrometer1.00 centimeter1.00 deciliter1.00 kilogram======1.00 pg1.00 ns1.00 μm1.00 cm1.00 dL1.00 kg======1.00×10−12 g1.00×10−9 g1.00×10−6 m1.00×10−2 m1.00×10−1 L1.00×103 g


You can express a given measurement in more than one unit. If you express a measured quantity in two different metric units, then the two measurements are metric equivalents. Common metric equivalents are shown below.
 Length:



1,000 millimeters100 centimeters10 millimeters===1 meter1 meter1 centimeter


 Mass:



1,000 milligrams1,000 grams==1 gram1 kilogram


 Volume:



1 liter=1,000 milliliters


Lesson Summary
 The metric system is an international decimalbased system of measurement.
 The metric system uses a number of prefixes along with the base units.
 The prefixes in the metric system are multiples of 10.
 A base unit is one that cannot be expressed in terms of other units
 If you express a measured quantity in two different metric units, then the two measurements are metric equivalents.
Further Reading / Supplemental Links
The following website provides more information about the metric system and measurements in chemistry.
Review Questions
Fill in the blanks in Table below.
Prefix  Meaning  Symbol 

pico 

p 
nano  ?  n 
? 


milli 

? 
centi  ?  c 
deci 

? 
? 

k 
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