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Measurement & Measurement & ConversionsConversions
Get ready for some math!!!!
Scientific NotationScientific NotationUsed for very large or very small
numbersAll numbers are represented by a
number between 1 and 10 multiplied by a power of 10
The number of places the decimal point has moved determines the power of 10. ◦ If the power is positive, the decimal point
will move to the ◦ If the power is negative, the decimal point
will move to the left
MeasurementMeasurementMeasurements and calculations
allow for some of the properties of substances to be determined (mass, density)
Scientific Notation is often used because measurements in chemistry can be very large or very small
Convert the following numbers Convert the following numbers to scientific notationto scientific notation
24500
356
0.000985
0.222
12200
Convert the following scientific Convert the following scientific notation numbers to regular notation numbers to regular numbersnumbers
4.2 x 103
2.15 x 10-4
3.14 x 10-6
9.22 x 105
9.57 x 102
Significant FiguresSignificant FiguresAll measured quantities are
generally reported in a way that the last digit is UNCERTAIN.
All other digits are considered SIGNIFICANT.
Rules for Sig FigsRules for Sig Figs
1. Nonzero digits are always significant.
22.6 kg has 3 significant figures453.9 m has 4 sig figs
2. Zeros between nonzero digits are significant.
20.3 kg has 3 sig figs87009 L has 5 sig figs
Rules for Sig Figs cont’dRules for Sig Figs cont’d
3. Zeros in front of nonzero digits are not significant (they simply are decimal place holders)
0.0009876 has 4 sig figs 0.0008 has 1 sig fig4. Zeros both at the end of a
number and to the right of a decimal point are significant
85.00 kg has 4 sig figs 9.0700000000 has 11 sig figs
Rules for Sig Figs cont’dRules for Sig Figs cont’d5. Zeros both at the end of a number
but to the left of a decimal point may not be significant. If a zero has not been measured or estimated, it is NOT SIGNIFICANT. A decimal point placed after zeros indicates that the zeros are significant.
2000 m has one significant figure
2000. m has four sig figs
Rules for CalculationsRules for CalculationsMultiplication or Division –
◦Final answer has the smallest # of sig figs
◦DO NOT ROUND UNTIL THE VERY END.
Addition or Subtraction – ◦Result cannot have more decimals
places than the unit with the smallest # of decimal places
Rules for CalculationsRules for CalculationsIf a calculation has both
multiplication (or division) and addition/subtraction, round after each operation.
EXACT VALUES HAVE UNLIMITED SIG FIGS
2 MOLECULES ARE 2 MOLECULES. = COUNT VALUE
SI UnitsSI Units
MeasurementMeasurement SymbolSymbol UnitUnit AbbreviationAbbreviation
LengthLength ll metermeter mm
MassMass MM kilograkilogramm
kgkg
TimeTime tt secondsecond ss
Therm. TempTherm. Temp TT kelvinkelvin KK
Amount of Amount of substancesubstance
nn molemole molmol
PrefixesPrefixes
PrefixPrefix SymbolSymbol MeaningMeaning
MegaMega MM 101066
KiloKilo KK 101033
DeciDeci DD 1010-1-1
CentiCenti CC 1010-2-2
MilliMilli MM 1010-3-3
MicroMicro 1010-6-6
Conversion in MetricsConversion in Metrics
K H D M D C M
Find the number of m in 2.35 km.
Find the number of km in Find the number of km in 756 m756 m
Conversion FactorsConversion FactorsA ratio that is derived from the
equality of two different units that can be used to convert from one unit to the other
5 dozen eggs = how many individual eggs?1 dozen = 12
individual
5 dozen x 12 individual = 60 individual eggs
1 dozen
CONVERSION FACTOR
How many g is 8503 mg?How many g is 8503 mg?
How many mm is 0.331 How many mm is 0.331 km?km?
Derived UnitsDerived UnitsUnits derived from the seven base unitsVolume= l x w x h (m3) Volume
◦ The most common used unit for volume is cm3.◦ 1cm3 = 1ml ◦ 1000cm3 = 1dm3 = 1000ml = 1L.
density◦ Density is the ratio of the mass of an object to its volume◦ Density = mass volume
Precision vs. AccuracyPrecision vs. AccuracyAccuracy- the accuracy of a
measurement is how close the measurement is to the true or actual value
Precision – is how closely several measurements made agree with one another.
Percent Error Analysis Percent Error Analysis
% Error = Measured value – Accepted Value
Accepted value