Topic: The Metric System
Do Now: Calculate the volume of Fe.
What element is Fe?
mass of Fe(s) = 15.9 g
density of Fe(s) = 7.87 g/cm3
Measurement up to 1790:
Not a pretty picture!
Measurement requires standard
and until 1790’s
every region had own standard
Systeme International (SI)
• French Academy of Sciences created
the metric system in 1790*
– Originally, earth-based standards
– Volume & mass linked to length
– Larger & smaller multiples of each unit
related by powers of 10 = metric system
*updated every few years (particularly in
in 1960 and 1991)
Standards
• “standard: something used as comparison
for measuring”
– standard must:
• be available for everyone to use to
check measurements
• be something in nature that is same
everywhere
• never vary
What is a second?
defined in terms of electron
transitions in Cs-133
(Caesium – an element)
What is a meter?
distance light travels in vacuum
in 1/299,792,458 th of second
What is a Liter?
• defined as cube measuring
10 centimeters on each side
(1000 cm3)
10 cm
• Liter based on meter, which is
based on Earth
10 cm
What is a kilogram?
defined as mass 1 Liter water
at 4°C
Why water?
10 cm
kilogram is based on liter,
which is based on meter,
which is based on Earth
10 cm
For Water only:
Prototype kilogram
stored in vault in
France
Smaller Units
• 1/10 of a meter = decimeter (dm)
• 1/100 of a meter = centimeter (cm)
• 1/1000 of a meter = millimeter (mm)
Larger Units
• 10 meters = dekameter (dam)
• 100 meters = hectometer (hm)
• 1000 meters = kilometer (km)
Don’t copy….
where can
you find?
Prefixes in the SI System
Prefix
Symbol
Value
Power
Use
Giga
G
1,000,000,000
109
Gigabyte
Mega
M
1,000,000
106
Megamillion
Kilo
k
1,000
103
kilometer
deci
d
0.1
10-1
decimeter
centi
c
0.01
10-2
centimeter
milli
m
0.001
10-3
millimeter
micro

0.000001
10-6
micrometer
nano
n
0.000000001
10-9
nanometer
Fundamental or Base Units
• Based on object or event in nature
• The SI system has 7 fundamental units
*label on Ref table
7 Fundamental Quantities of SI
Quantity
Length
Name
Abbreviation
meter
m
kilogram
second
kg
s
Temperature
kelvin
K
Amount of
Substance
Mole
mol
Luminous
Intensity
candela
cd
Electric Current
ampere
A
Mass
Time
Derived Units
• Combinations of fundamental units
• Examples:
–
–
–
–
Speed (meters/second)
Area (Length x Width)
Volume (Length x Width x Height)
Density (Mass / Volume)
Prefixes
• prefixes can be used with all 7
fundamental units!
– Kilometer
– Milliliter
– Centigram
– Microsecond
– Nanokelvin
1790 - Jefferson
• Proposed decimal-based measurement
system for United States
• Didn’t have prefix idea and system
had too many names….and so we are
stuck using feet, inches, cups, ounces,
etc…
Kids
Have
Dropped
Dead
Converting
Metric
Ladder Method
1
2
KILO
1000
Units
3
HECTO
100
Units
DEKA
10
Units
DECI
0.1
Unit
Meters
Liters
Grams
How do you use the “ladder” method?
CENTI
0.01
Unit
MILLI
0.001
Unit
4 km = _________ m
1st – Determine your starting point.
Starting Point
2nd – Count the “jumps” to your ending point.
How many jumps does it take?
3rd – Move the decimal the same number of
jumps in the same direction.
Ending Point
4. __. __. __. = 4000 m
1
2
3