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
The first standardized system of measurement: The Metric system Metric System & SI The first standardized system of measurement: The Metric system Developed in France in 1795 Named based on French word for “measure” based on powers of 10
Components of SI The SI has 3 parts: base units derived units prefixes
SI: Base Units length meter m mass kilogram kg time second s 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
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
Prefixes Prefix Symbol Numerical Multiplier Exponential Multiplier 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
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. Why do substances expand as temp. increases? (exception??)
-freezing point of water = -boiling point of water = Celsius scale -freezing point of water = -boiling point of water = Kelvin scale, K (SI Base unit) 0 K (absolute zero) = K = °C + 273.15 °C = K – 273.15
Units of Energy Joule (J) = SI unit of energy Calorie (cal) 1 J = 0.2390 cal 1 cal = 4.184 J How many calories are there in 75.5 J?
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 The speed of a skyrocket is measured and found to be 145.36 m/s. What is the rocket’s speed in km/h?