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

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.

Components of the SI System The SI system of measurement has 3 parts: base units derived units prefixes

SI: Base Units length meter m mass gram g time second s Physical Quantity Unit Name Symbol length meter m mass gram g time second s electric current ampere A temperature Kelvin K amount of substance mole mol luminous intensity candela cd

SI: Derived Units area square meter m2 volume cubic meter m3 speed Physical Quantity Unit Name Symbol area square meter m2 volume cubic meter m3 speed meter per second m/s acceleration second squared m/s2 weight, force newton N pressure pascal Pa energy, work joule J

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: 1

Prefixes Prefix Symbol Numerical Multiplier Exponential Multiplier no prefix means: 1 100 deci d 0.1 10¯1 centi c 0.01 10¯2 milli m 0.001 10¯3 micro 0.000001 10¯6 nano n 0.000000001 10¯9 pico p 0.000000000001 10¯12 femto f 0.000000000000001 10¯15 atto a 0.000000000000000001 10¯18 zepto z 0.000000000000000000001 10¯21 yocto y 0.000000000000000000000001 10¯24

“Staircase” Method

Problem: convert 114.55 cm to km

Dimensional Analysis Factor-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

Dimensional Analysis Factor-Label Method Convert 6.5 km to m

Convert 3.5 hours to seconds

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

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??)

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

Units of Energy Joule (J) = SI unit of energy Calorie (cal) 1 J = 0.2390 cal 1 cal = 4.184 J