MeasurementMeasurement
How much? How long? How many?How much? How long? How many?
Exact and inexact numbersExact and inexact numbers
Exact number:Exact number: A number with no uncertainty itA number with no uncertainty it A dozen donuts, seven students, etc.A dozen donuts, seven students, etc.
Inexact number:Inexact number: A number that has a degree of A number that has a degree of
uncertainty in it; results anytime a uncertainty in it; results anytime a measurement is mademeasurement is made
Height of student; temperature of Height of student; temperature of studentstudent
Precision and AccuracyPrecision and Accuracy
Accuracy:Accuracy: How close a measured value is to How close a measured value is to
the actual (true) valuethe actual (true) value Precision:Precision:
How close the measured values How close the measured values are to each otherare to each other
Testing our knowledgeTesting our knowledge
How accurate?How accurate? Low accuracyLow accuracy
How Precise?How Precise? High precisionHigh precision
Testing our knowledgeTesting our knowledge
How accurate?How accurate? High accuracyHigh accuracy
How Precise?How Precise? Low precisionLow precision
Testing our knowledgeTesting our knowledge
How accurate?How accurate? High accuracyHigh accuracy
How Precise?How Precise? High precisionHigh precision
Systems of MeasurementSystems of Measurement
English:English: Commonly used in commerce and Commonly used in commerce and
homeshomes Inch, foot, pound, quart, and gallonInch, foot, pound, quart, and gallon
Metric systemMetric system Used worldwideUsed worldwide
SI systemSI system Revised in 1960 with improved unitsRevised in 1960 with improved units SI stands for “French Systeme SI stands for “French Systeme
International d’Unites”International d’Unites” Used by scientistsUsed by scientists
SI SystemSI System The Seven Base Units in the SI system:The Seven Base Units in the SI system:
Base quantityBase quantity Unit NameUnit Name Unit Unit AbbreviationAbbreviation
LengthLength MeterMeter mmMassMass gramgram ggTimeTime SecondSecond ssTemperatureTemperature kelvinkelvin KKAmount of Amount of substancesubstance
molemole mm
Electric currentElectric current ampereampere AALuminous intensityLuminous intensity candelacandela cdcd
Metric system prefixesMetric system prefixes
Common Common prefixesprefixes
For example,For example, 100 cm = 1 m100 cm = 1 m 1,000 mg = 1 gm1,000 mg = 1 gm
KiloKilo kk 1,0001,000
DeciDeci dd 1/101/10
CentiCenti cc 1/1001/100
MilliMilli mm 1/1,0001/1,000
LengthLength
Meter is the SI base unit of Meter is the SI base unit of lengthlength 1 meter=1.05 yards1 meter=1.05 yards A dime is about 1 mm thickA dime is about 1 mm thick
Or…1/1000 of a mOr…1/1000 of a m Your little finger is about 1 cm Your little finger is about 1 cm
acrossacross Or…1/100 of a mOr…1/100 of a m
Mass vs. WeightMass vs. Weight
MassMass A measure of the total quantity of A measure of the total quantity of
matter in an objectmatter in an object WeightWeight
A measure of the force exerted on A measure of the force exerted on an object by gravitational forcesan object by gravitational forces
If you weigh 60 kg on Earth, will If you weigh 60 kg on Earth, will you weigh more or less on the you weigh more or less on the moon? Why? moon? Why?
Mass vs. WeightMass vs. Weight How much does this astronaut How much does this astronaut
floating in space weigh?floating in space weigh?
What is the astronaut’s mass?
MassMass
Kilogram is the SI unit for massKilogram is the SI unit for mass Note that the prefixes are added Note that the prefixes are added
to gram not kilogram, i.e., to gram not kilogram, i.e., centigram, milligram, etc.centigram, milligram, etc.
10 pennies weigh about 1 gram10 pennies weigh about 1 gram 1 gram is 1/1,000 kilogram1 gram is 1/1,000 kilogram
Aspirin commonly is 325 mgAspirin commonly is 325 mg 1 milligram = 1/1000 gram1 milligram = 1/1000 gram
Area and volumeArea and volume
Area: measure of extent of a Area: measure of extent of a surfacesurface For a square, length vs widthFor a square, length vs width
Square feet, ftSquare feet, ft22
Square cm, cmSquare cm, cm22
Volume: measure of the amount Volume: measure of the amount of space occupied by an objectof space occupied by an object For a cube, side x side x sideFor a cube, side x side x side
Cubic feet, ftCubic feet, ft33
Cubic cm, cmCubic cm, cm33
VolumeVolume
Cubic meter (mCubic meter (m33) is the SI ) is the SI system base unit for volumesystem base unit for volume A mA m33 is too large to be used in the is too large to be used in the
chemistry lab, so cmchemistry lab, so cm33 is much is much more commonmore common
1 cubic cm (cm1 cubic cm (cm33 )= 1 milliliter (ml) )= 1 milliliter (ml) 1 liter is a volume equivalent to 1 liter is a volume equivalent to
that of a cube that isthat of a cube that is 10 cm x 10 cm x 10 cm or 1,000 cm10 cm x 10 cm x 10 cm or 1,000 cm33
SI UnitsSI Units
The best way to understand SI The best way to understand SI units is to use them in everyday units is to use them in everyday lifelife
Everyday examples
Measuring volumeMeasuring volume
Technique for measuring volume
TemperatureTemperature A measure of the hotness or A measure of the hotness or
coldness of an objectcoldness of an object Three scales:Three scales:
KelvinKelvin after William Kelvin (1824-1907)after William Kelvin (1824-1907) Does not use degree symbolDoes not use degree symbol
CelsiusCelsius After Anders Celsius (1701-1744)After Anders Celsius (1701-1744) Most commonly used in scienceMost commonly used in science
Three scalesThree scales KelvinKelvin
after British mathematician and physicist, after British mathematician and physicist, William Kelvin (1824-1907)William Kelvin (1824-1907)
Does not use degree symbolDoes not use degree symbol No negative numbersNo negative numbers
CelsiusCelsius after Swedish astronomer, Anders Celsius after Swedish astronomer, Anders Celsius
(1701-1744)(1701-1744) Most commonly used in scienceMost commonly used in science
FahrenheitFahrenheit After German physicist, Gabriel Fahrenheit After German physicist, Gabriel Fahrenheit
(1686-1736)(1686-1736) Based on the temperature of a salt-ice mixture Based on the temperature of a salt-ice mixture
as 0as 0°F°F and the boiling point of mercury at 600 and the boiling point of mercury at 600°F°F
Common temperaturesCommon temperatures
Freezing point of waterFreezing point of water 00°C=32°F=273.15 K°C=32°F=273.15 K
Room temperatureRoom temperature 2222°C=72°F=295 K°C=72°F=295 K
Boiling point of waterBoiling point of water 100100°C=212°F=373 K°C=212°F=373 K