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MeasurementMeasurement
The Metric System and SI UnitsThe Metric System and SI UnitsConverting UnitsConverting Units
Measuring Volume and MassMeasuring Volume and MassDensityDensity
Measuring TemperatureMeasuring Temperature
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SI UnitsSI Units
Many different systems for measuring the world around us have developed over the years.
People in the U.S. rely on the English System.
Scientists make use of SI units so that we all are speaking the same measurement language.
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Data, results and unitsData, results and unitsDataData
Measurements and observations.ResultsResults
Data obtained from an experiment.May be converted using known equations.
UnitsUnitsDefines the quantities being measured.All measurements must have units.
To communicate our results, we must use standard units
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Units are importantUnits are important
45 000 has little meaning, just a number
$45,000 has some meaning - money
$45,000/yr more meaning - person’s salary
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Measurements Measurements English units. English units.
- Still commonly used in the United States.Weight ounce, pound, tonLength inch, foot, yard, mileVolume cup, pint, quart, gallon
Not often used in scientific workNot often used in scientific work - Very confusing and difficult to keep
track of the conversions needed.
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MeasurementMeasurementEnglish units.English units. Vary in size so you must
memorize many conversion factors.
Common English measures of volumeCommon English measures of volume1 tablespoon = 3 teaspoons1 cup = 16 tablespoons1 pint = 2 cups1 quart = 2 pints1 gallon = 4 quarts1 peck = 2 gallons1 bushel = 4 pecks
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ExampleExample
How many teaspoons in a barrel of oil?1 barrel of oil = 42 gallons1 gallon = 4 quarts1 quart = 4 cups1 cup = 16 tablespoons1 tablespoon = 3 teaspoons
1 bbl x 42 x 4 x 4 x 16 x 3galbbl
qtgal
cupqt
tblcup
tsptbl
= 32 256 tsp
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Metric UnitsMetric Units One base unit for each type of measurement. Use a prefix to change the size of unit.
Some common base units.TypeType NameName SymbolSymbolMass gram gLength meter mVolume liter L Time second sEnergy joule J
MeasurementMeasurement
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Metric prefixesMetric prefixes
Changing the prefix alters the size of a unit.PrefixPrefix Symbol Symbol Factor Factor
mega M 106 1 000 000
kilo k 103 1 000
hecto h 102 100
deka da 101 10
base - 100 1
deci d 10-1 0.1
centi c 10-2 0.01
milli m 10-3 0.001
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SI unitsSI unitsSI - System InternationalSystem International
Systematic subset of the metric system.Only uses certain metric units.
Mass kilogramsLength metersTime secondsTemperature kelvinAmount moleCurrent ampere
Other SI units are derived from SI base units.
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Example. Metric conversionExample. Metric conversion
How many milligrams are in a kilogram?
1 kg = 1000 g1 g = 1000 mg
1 kg x 1000 x 1000
= 1 000 000 mg
kgg mg
g
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Converting unitsConverting units
Factor label methodFactor label method
•Regardless of conversion, keeping track of units makes thing come out right
•Must use conversion factors- The relationship between two units
•Canceling out units is a way of checking that your calculation is set up right!
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Common conversion factorsCommon conversion factorsEnglish FactorFactor
1 gallon = 4 quarts 4 qt/gal1 mile= 5280 feet 5280 ft/mile1 ton = 2000 pounds2000 lb/ton
Common English to Metric conversions FactorFactor
1 liter = 1.057 quarts 1.057 qt/L1 kilogram = 2.2 pounds 2.2 lb/kg1 meter = 1.094 yards 1.094 yd/m1 inch = 2.54 cm 2.54 cm/inch
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ExampleExampleCreatinine is a substance found in blood. If
an analysis of blood serum sample detected 0.58 mg of creatinine, how many micrograms were present?
= 10-6 = micro
0.580 mg = 580 g10-3 g1 mg( ) 1 g
10-6 g( )
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ExampleExampleA nerve impulse in the body can travel as
fast as 400 feet/second.
What is its speed in meters/min ?
Conversions Needed
1 meter = 3.3 feet1 minute = 60 seconds
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m 400 ft 1 m 60 secmin 1 sec 3.3 ft 1 min
ExampleExample
m 400 ft 1 m 60 secmin 1 sec 3.3 ft 1 min? = x x
? = x x
mmin ....Fast7273
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Measuring volumeMeasuring volume
VolumeVolume - the amount of space that an object occupies.
• The base metric unit is the liter (L)liter (L).• The common unit used in the lab is the
milliliter (mL)milliliter (mL).• One milliliter is exactly equal to one cmcm33.• The derived SISI unit for volume is the mm33
which is too large for convenient use.
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Measuring massMeasuring mass
MassMass - the quantity of matter in an object.WeightWeight - the effect of gravity on an object.
Since the Earth’s gravity is relatively constant, we can interconvert between weight and mass.
The SI unit of mass is the kilogram (kg)kilogram (kg). However, in the lab, the gram (g)gram (g) is more commonly used.
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DensityDensityDensity is property of a substance based on
its ratio of mass to volume.
Common units are g / cm3 or g / mL.
g / cm3 g / cm3
Air 0.0013 Bone 1.7 - 2.0Water 1.0 Urine 1.01 - 1.03Gold 19.3 Gasoline 0.66 - 0.69
Density = Mass
Volumecm3 = mL
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Example.Example.Density calculationDensity calculation
What is the density of 5.00 mL of a fluid if ithas a mass of 5.23 grams?
d = mass / volume d = 5.23 g / 5.00 mLd = 1.05 g / mL
What would be the mass of 1.00 liters of thissample?
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Example.Example.Density calculationDensity calculation
What would be the mass of 1.00 liters of the fluid sample?
The density was 1.05 g/mL.density = mass / volume
so mass = volume x densitymass = 1.00 L x 1000 x 1.05
= 1.05 x 103 g
mlL
gmL
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Temperature conversionTemperature conversion
Temperature - measure of heat energy.
Three common scales usedFahrenheit, Celsius and Kelvin.
oF = 32oF + (oC) X
oC = (oF - 32oF)
K = (oC + 273) X SI unit
5oC9oF
9oF5oC
1 K1oC
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Example. Example. ooF to F to ooC C
If it is 20 oF outside, what is it in oC ?
oC = (oF - 32oF) 5oC9oF
oC = (20oF - 32oF) 5oC9oF
oC = -6.7 (two significant figures in 20oF)
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