chemistry - measurements

probably wont contain all the notes/lab questions

motto to remember measurements

• king

• henry

• died

• unexpectedly

• drinking

• chocolate

• milk

actual measurements for motto

• KILOmeters

• HECTOmeters

• DECAmeter

• unit (mL, L,…)

• DECImeters

• CENTImeters

• MILImeters

accuracy

evaluation of how close a measurement is to the acceptable value of the measurement

precision

evaluates how exactly a measurement is made

SigFig Rule #1

SigFigs only apply to measured data

• not counted #s, pure #s, or fractions like 60 secs/1 min

SigFig Rule #2

all NONZERO digits are significant

• 112.54 - 5 sigfigs

rule #3

all ZEROs between NONZEROS digits are significant (sandwiched)

• 10.6 - 3 sigfigs

rule #4

decimal points define Significant 0s

if a decimal point is present, all zeros to the ____ of the last nonzero digits are significant

right

when are zeros not significant

• no decimal present

• no zeros to the LEFT of the FIRST nonzero digit

  • .050 - 2 sigfigs

if a decimal is not present, the trailing zeros are _____

not significant

rule #5

a decimal must follow and estimated zero in ones place

• if estimated value of measurement is 0 in ones place, it’s impossible tot tell precision

when adding/subtracting sigfigs, determine the least amount of ____

decimal places, give answer in least amount of given decimal places

• 12.3456 + 3.8 = 16.1456 = 16.1

when multiplying/dividing sig figs, determine SMALLEst # of ____

sigfigs, give answer in same lowest amount of sigfigs

• 34.6 × 2 = 69.2 = 70

• 46.9000 / 3.3 = 14.2121 = 14

quantitive data

numerical data

• discrete (counting)

• continuous (measurement)

qualitive data

descriptive data based on observations (words)

• involves 5 senses

metric prefixes

what do sigfigs do

help scientist determine precision of instrument

Things we measure when we measure

• amount of matter

• mass

• volume

• density

weight is measured in ____

newtons

1 lb is = ___ N (newtons)

4.4482216 N

mass is the measure of the amount of ___ in a substance

matter (g/kg)

volume is the amount of ___ an object occupies

space (mL/L)

what is density measuring?

• the amount of mass per volume (kg/m squared or g/cm squared)

• density = mass/volume

water displacement (volume measuring method)

• place object in graduated cylinder with marked volume

• add object and read the change in volume with object and subtract to find the volume of the object