Systems of Measurement Why do we need a standardized system of measurement? – Scientific community is global – An international “language” of measurement.

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 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

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 UnitsPhysical Quantity Unit Name Symbol

area square meter m2

volume cubic meter m3

speed meter persecond

m/s

accelerationmeter per

second squaredm/s2

weight, force newton N

pressure pascal Pa

energy, work joule J

PrefixesPrefix Symbol Numerical Multiplier

ExponentialMultiplier

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

PrefixesPrefix Symbol Numerical Multiplier

ExponentialMultiplier

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

Mass metric ton, t = 103 kg

Areahectare, ha = 1 hm2

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??)

Celsius scale-freezing point of water =-boiling point of water =

Kelvin scale, K (SI Base unit)-freezing point of water = -boiling point of water =

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 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

Dimensional AnalysisFactor-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?