significant measurements and SI units

Mass

• kg

• kilogram

length

• m

• metre

time

• s

• second

electrical current

• a

• ampere

temperature

• k

• kelvin

amount of subtsance 

• mol

• mole

luminous intensity 

• cd

• candela

SI derived units

made from base units

force

• N

• newton

energy

• J

• joules

temperature - SI derived unit

• ºC

• degree celsius

pressure

• Pa

• pascal

power

• w

• watt

electrical potential 

• v

• volt

non SI units used with SI units

exception for these units used in scientific literature 

time non SI units

• min - minute

• h - hour

• d - day

• a - year

volume

• litre

• L

mass

• metric tonne

• t

pressure

• standard atmosphere

• atm

length

• astronomical unit 

• au

unit names and symbol rules

• SI units represent SI values

• small letters

• unaltered in plural

• names and units are not mixed

• no abbreviations

• value must be 1+ (change unit if not)

• space between value and symbol

numerical notation

• space after groups of 3 digits

• no space if only four digits

• unit symbols only with mathematical opporations 

• use symbols throughout equation

prefixes

added to unit names to produce mulitples and submulitples

significant digits

estimated digits in a number through educated observation

significant zero

• zero trailing a non-zero number

• indicates precision

leading/placeholder zero

• zero before non-zero number

• cannot be estimated