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 KilogramKilogram kgkgTimeTime 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 Everyday examples

Measuring volumeMeasuring volume

Technique for measuring volumTechnique for measuring volumee

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