Systems of Measurement

1
Systems of Measurement

• Why do we need a standardized system of
  measurement?
• Scientific community is global
• An international language of measurement allows
  ALL scientists to communicate

2
Metric System SI

• The first standardized system of measurement the
  Metric system
• Developed in France in 1791
• Named based on French word for measure
• based on the decimal (powers of 10)
• Systeme International d'Unites(International
  System of Units)
• Modernized version of the Metric System
• Abbreviated by the letters SI.
• Established in 1960, at the 11th General
  Conference on Weights and Measures.
• Units, definitions, and symbols were revised and
  simplified.

3
Components of the SI System

• The SI system of measurement has 3 parts
• base units
• derived units
• prefixes

4
SI Base Units
Physical Quantity Unit Name Symbol
length meter m
mass kilogram kg
time second s
electric current ampere A
temperature Kelvin K
amount of substance mole mol
luminous intensity candela cd
5
SI Derived Units
Physical Quantity Unit Name Symbol
area square meter m2
volume cubic meter m3
speed meter per second m/s
acceleration meter per second squared m/s2
weight, force newton N
pressure pascal Pa
energy, work joule J
6
Prefixes
Prefix Symbol Numerical Multiplier Exponential Multiplier
yotta Y 1,000,000,000,000,000,000,000,000 1024
zetta Z 1,000,000,000,000,000,000,000 1021
exa E 1,000,000,000,000,000,000 1018
peta P 1,000,000,000,000,000 1015
tera T 1,000,000,000,000 1012
giga G 1,000,000,000 109
mega M 1,000,000 106
kilo k 1,000 103
hecto h 100 102
deca da 10 101
no prefix means no prefix means 1 100
7
Prefixes
Prefix Symbol Numerical Multiplier Exponential Multiplier
no prefix means no prefix means 1 100
deci d 0.1 101
centi c 0.01 102
milli m 0.001 103
micro m 0.000001 106
nano n 0.000000001 109
pico p 0.000000000001 1012
femto f 0.000000000000001 1015
atto a 0.000000000000000001 1018
zepto z 0.000000000000000000001 1021
yocto y 0.000000000000000000000001 1024
8
Staircase Method
9
Problem convert 114.55 cm to km
10
Dimensional AnalysisFactor-Label Method

• Multiply by conversion factor (a fraction that
  relates the original unit and the desired unit)
• Conversion factor is always equal to 1.
• Numerator and denominator should be equivalent
  measurements.
• When measurement is multiplied by conversion
  factor, original units should cancel

11
Dimensional AnalysisFactor-Label Method

• Convert 6.5 km to m

12

• Convert 3.5 hours to seconds

13
Units of Volume

• The space occupied by matter
• Derived from length (m3)
• Non-SI Liter
• 1000 cm3 1 L 1 mL 1 cm3
• Instruments graduated cylinder, pipet, buret,
  volumetric flask

14
Units of Temperature

• Temperature a measure of how hot or cold an
  object is (the avg. kinetic energy of particles
  in matter)
• Heat flows from higher temp. to lower temp.
• Substances expand as temp. increases
  (exception??)

15

• Celsius scale
• -freezing point of water
• -boiling point of water
• Kelvin scale
• -freezing point of water
• -boiling point of water
• 0 K (absolute zero) -273.15C
• K C 273 C K - 273

16
(No Transcript)
17
Units of Energy

• Joule (J) SI unit of energy
• Calorie (cal)
• 1 J 0.2390 cal
• 1 cal 4.184 J