METRIC SYSTEM
There are two reasons why the metric system is used in the lab:

The unit measurements are standardized in such a way that they will never change.

The units are based on powers of 10 which make the conversions between units simple and easier than our
English system.
There are 7 fundamental measurements:
MEASUREMENT
mass
length
temperature
time
amount of substance
electric current
luminous intensity
S.I. BASE UNIT
kilogram
meter
Kelvin
second
mole
ampere
candela
SYMBOL
kg
m
K
s
mol
A
cd
All measurements are either a fundamental measurement or a derived measurement (consist of 2 or more
fundamental measurements).
In the lab, the commonly used units are:
MEASUREMENT
mass
length
temperature
time
volume
UNIT
gram
centimeter
Celsius
second
liter
SYMBOL
g
cm
°C
s
L
The metric system uses prefixes to obtain the different magnitudes of the base units. Each prefix represents a power
of 10 and has a symbol to go along with it.
PREFIX
exa
peta
tera
giga
mega
kilo
hecto
deka
base unit
deci
centi
milli
micro
nano
pico
femto
atto
SYMBOL
E
P
T
G
M
k
h
da
d
c
m
μ
n
p
f
a
POWER
18
10
15
10
12
10
9
10
6
10
3
10
2
10
1
10
0
10
−1
10
−2
10
−3
10
−6
10
−9
10
−12
10
−15
10
−18
10
By using the symbol for the prefix and base unit, one can get the symbol for the different units.
centimeter
→
cm
milliliter
→
mL
microsecond
→
μs
megameter
→
Mm
Since each prefix represents a power of 10, by knowing what the prefix means you can convert from one metric unit to
another by just moving the decimal the right number of places in the correct direction. There are 2 basic rules to
follow in doing this:
Number of Places to Move Decimal: Find the difference between the powers of 10 for the prefixes involved.
Direction to Move Decimal: Move the decimal in such a way so that the smaller unit (lower power of 10) ends
up with the larger number.
Examples:
change 150 mL to L


change 2.56 kg to cg
−3
0
Since milli is 10 and L is the base unit it is 10 .
Therefore the difference between the two units is
3 decimal places.
Since mL is smaller than L, the decimal will move
to the left to get a smaller number for the L (thus
mL ends up the larger number).


3
−2
Since kilo is 10 and centi is 10 , the difference
between the two units is 5 decimal places.
Since cg is smaller than kg, the decimal will move
to the right so cg gets a larger number than kg
2.56 kg = 256000 cg
150 mL = 0.15 L
Some other equivalences to note:
3
1 mL = 1 cm
3
1 L = 1 dm
−10
1 Å = 10 m (Å is angstrom, a common length measurement used for extremely small particles)
1 nm = 10 Å