The Metric System Simple & Consistent

Measurement up to 1790: Not a pretty picture! standardMeasurement requires a standard and until about the 1790’s every region had it’s own standard

Standards “A standard is something that is used as a comparison for measuring” available for everyone –The standard must be available for everyone to use to check measurements a standard should be something in nature that is the same all over the earth –means a standard should be something in nature that is the same all over the earth never vary –The standard must never vary

1585 – Simon Stevin Introduced the use of decimals in mathematics in Europe Predicted the universal introduction of decimal coinage, measures and weights

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

Systeme International (SI) Based on the 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 in 1960

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

Basic Standard = Earth 1.The unit of length was to be a portion of the Earth's circumference

Internal Consistency related 2.Units for capacity (volume or space) and mass related to the unit of length

Ease of Use - Calculations multiplying or dividing the basic units by factors of 10 3.Larger and smaller units are created by multiplying or dividing the basic units by factors of 10

Fundamental or Base Units Based on object or event in nature 7The SI system has 7 fundamental units You already know 4. What are they?

AbbreviationNameQuantity 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 Many, many derived units Examples: –Speed or meters/second –Area or Length X Width –Volume or Length X Width X Height –Density or Mass / Volume

Ease of Use - Names prefixes Larger & smaller multiples of each unit named by a series of prefixes relating them to the base unit

Smaller & Larger Units 1/10 of a meter = decimeter (dm) 1/100 of a meter = centimeter (cm) 1/1000 of a meter = millimeter (mm) 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 The prefixes can be used with all 7 fundamental units! meter –Kilometer liter –Milliliter gram –Centigram second –Microsecond kelvin –Nanokelvin

Jefferson Proposed a decimal-based measurement system for the United States Didn’t come up with the prefix idea and his system had too many names

1792 – U.S. Mint Produced world’s first decimal currency (one dollar = 100 cents)

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

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

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

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

What is a kelvin? The 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

What is a mole? amount of substance which has as many elementary particles as there are atoms in kilogram of carbon-12

Prototype kilogram in France