Metric System Simple & Consistent

Measurement up to 1790: not a pretty picture! standard measurement requires a recognizable standard for all but… until 1790’s every region had own standards

Standards “standard: something used as comparison for measuring” –standard must: available for everyonebe available for everyone to use be something in nature that is same everywherebe something in nature that is same everywhere never varynever vary

1585 – Simon Stevin introduced use of decimals in Europe –to allow for parts of a whole predicted universal introduction of decimal coinage, measures and weights

1670 – Gabriel Mouton based on size of earth1 st to propose decimal system of measurement based on size of earth Earth-based standard: 1  of longitude Earth is standard available to everyone! What an idea!

Systeme International (SI) based on metric system invented in 1790* –originally, earth-based standards –volume & mass linked to length –larger & smaller multiples of each unit related by powers of 10 *updated every few years (major changes in 1960 and 1991)

created 1790 – French Academy of Sciences created the metric system 3 Requirements

# 1 Basic Standard = Earth unit of length is portion of Earth's circumference

#2 Internal Consistency relatedunits for capacity (volume/space) and mass related to unit of length

#3 Ease of Use - Calculations multiplying or dividing basic units by factors of 10larger and smaller units created by multiplying or dividing basic units by factors of 10

Fundamental (Base) Units based on object/event in nature 7SI system has 7 fundamental units probably already know 4 of them any guesses as to which ones you know?

ABBREVIATIONUNITQUANTITY mmeterlength kgkilogrammass Kkelvintemperature ssecondtime cdcandela luminous intensity Aampere electric current molmole amount of substance 7 Fundamental Quantities of SI

Derived Units combinations of fundamental units examples: –speed –speed (meters/second) –area –area (length x width) –volume –volume (length x width x height) –density –density (mass / volume)

Ease of Use - Names larger & smaller multiples of same unit named by prefixes series of prefixes relating to base unit

smaller units 1/10 of meter = decimeter (dm) 1/100 of meter = centimeter (cm) 1/1000 of meter = millimeter (mm) larger units 10 meters = dekameter (dam) 100 meters = hectometer (hm) 1000 meters = kilometer (km)

UsePowerValueSymbolPrefix gigabyte ,000,000,000 Ggiga megamillion ,000,000Mmega kilometer ,000kkilo decimeter ddeci centimeter ccenti millimeter mmilli micrometer  micro nanometer nnano Prefixes in the SI System

Prefixes used for all 7 fundamental units! meter –kilometer liter –milliliter gram –centigram second –microsecond kelvin –nanokelvin

Jefferson proposed decimal-based measurement system for US cons: no prefixes & too many names

1792 – U.S. Mint produced world’s first decimal currency (one dollar = 100 cents) 100 cents in dollar 4 quarters in dollar 10 dimes in dollar 20 nickels in dollar can see how this can be confusing: -names not related to each other -no consistency with parts of dollar

What is a meter? / 1790: 1/10,000,000 th of distance from North pole to equator / 1983: distance light travels in vacuum in 1/299,792,458 th of second

Liter What is a Liter? defined as cube measuring 10 centimeters on each side (1000 cm 3 ) 10 cm liter based on meter, which is based on Earth

kilogram What is a kilogram? 10 cm defined as mass of 1 liter water at 4°C Why water Why water? kilogram is based on liter, which is based on meter, which is based on Earth

second What is a second? originally defined as 1/86,400th of average solar day defined now in terms of electron transitions in Cs- 133

Kelvin What is a Kelvin? Kelvin is defined in terms of water & absolute zero 0 K = Absolute zero bp of H 2 O = 100  C = 373 K mp of H 2 O = 0  C = 273 K

mole What is a mole? amount any substance that has as many particles as # atoms found in kg of carbon-12

kilogram prototype kilogram stored in vault in France