Chapter 3 Measurements And Their Scientific Uncertainty

1y ago
13 Views
2 Downloads
3.56 MB
13 Pages
Last View : 1d ago
Last Download : 2m ago
Upload by : Axel Lin
Transcription

Section 3.1Measurements and TheirUncertaintyChapter 3 ScientificMeasurement OBJECTIVES: Convertmeasurements toscientific notation.Click to add text12Section 3.1Measurements and TheirUncertainty Section 3.1Measurements and TheirUncertaintyOBJECTIVES: Distinguishamongaccuracy, precision, anderror of a measurement.OBJECTIVES: Determinethe number ofsignificant figures in ameasurement and in acalculated answer.3Measurements Qualitative measurements are words, suchas heavy or hot Quantitative measurements involvenumbers (quantities), and depend on:1) The reliability of the measuring instrument2) the care with which it is read this isdetermined by YOU! Scientific Notation Coefficient raised to power of 10 Reviewed earlier this semester!54Accuracy, Precision, and Error It is necessary to make good,reliable measurements in the lab Accuracy how close ameasurement is to the true value Precision how close themeasurements are to each other(reproducibility)6

Precision and AccuracyAccuracy, Precision, and Error Accepted value the correctNeitheraccuratenor precisePrecise,but notaccuratevalue based on reliablereferences Experimental value thevalue measured in the labPreciseANDaccurate78Why Is there Uncertainty?Accuracy, Precision, and ErrorMeasurements are performed withinstruments, and no instrument can read toan infinite number of decimal places Which of the balances shown has thegreatest uncertainty in measurement? Error accepted value exp. valueCan be positive or negative Percent error the absolute value ofthe error divided by the accepted value,then multiplied by 100% error % error accepted value x 100% 910Figure 3.5 Significant Figures - Page 67Significant Figures inMeasurements Significant figures in aWhich measurement is the best?What is themeasured value?measurement include all of thedigits that are known, plus onemore digit that is estimated. Measurements must be reportedto the correct number ofsignificant figures.What is themeasured value?What is themeasured value?1112

Rules for Counting SignificantFiguresRules for Counting SignificantFiguresZerosNon-zeros always count assignificant figures:Leading zeroes do not count assignificant figures:3456 has4 significant figures0.0486 has3 significant figures13Rules for Counting SignificantFigures14Rules for Counting SignificantFiguresZerosZerosTrailing zeros are significant onlyif the number contains awritten decimal point:Captive zeroes always count assignificant figures:9.300 has4 significant figures16.07 has4 significant figures15Sig Fig Practice #1Rules for Counting SignificantFiguresHow many significant figures in the following?1.0070 m 5 sig figsTwo special situations have anunlimited number of significantfigures:1. Counted itemsa)1617.10 kg 4 sig figs100,890 L 5 sig figs3.29 x 10 s 3 sig figs323 people, or 425 thumbtacksThese comefrommeasurements0.0054 cm 2 sig figs2. Exactly defined quantitiesb) 60 minutes 1 hour3,200,000 5 dogs 172 sig figsunlimitedThis is acounted value18

Significant Figures inCalculationsRounding Calculated Answers In general a calculated answer cannotbe more precise than the leastprecise measurement from which itwas calculated. Ever heard that a chain is only asstrong as the weakest link? Sometimes, calculated values need tobe rounded off. RoundingDecide how many significant figuresare needed (more on this very soon) Round to that many digits, countingfrom the left Is the next digit less than 5? Drop it. Next digit 5 or greater? Increase by 1 1920- Page 69Rounding Calculated Answers Addition and Subtraction Theanswer should berounded to the same numberof decimal places as theleast number of decimalplaces in the problem.Be sure to answer thequestion completely!21- Page 7022Rounding Calculated Answers Multiplication and Division Roundthe answer to thesame number of significantfigures as the least number ofsignificant figures in theproblem.2324

- Page 7125Sig Fig Practice #2CalculationCalculator says:Answer3.24 m x 7.0 m22.68 m100.0 g 23.7 cm34.219409283 g/cm3 4.22 g/cm3223 m20.02 cm x 2.371 cm 0.04742 cm20.05 cm2710 m 3.0 s236.6666667 m/s240 m/s1818.2 lb x 3.23 ft5872.786 lb·ft5870 lb·ft1.030 g x 2.87 mL2.9561 g/mL2.96 g/mL27Section 3.3The International System ofUnitsSig Fig Practice #3CalculationCalculator says:Answer3.24 m 7.0 m10.24 m10.2 m100.0 g - 23.73 g76.27 g76.3 g0.02 cm 2.371 cm2.391 cm2.39 cm713.1 L - 3.872 L709.228 L709.2 L1818.2 lb 3.37 lb1821.57 lb1821.6 lb2.030 mL - 1.870 mL0.16 mL0.160 mL OBJECTIVES: ListSI units ofmeasurement andcommon SI prefixes.*Note the zero that has been added.2930

Section 3.3The International System ofUnits Section 3.3The International System ofUnitsOBJECTIVES: DistinguishOBJECTIVES: Convertbetween themass and weight of anobject.between theCelsius and Kelvintemperature scales.3132International System of UnitsInternational System of Units Metric system is now revised and Measurements depend uponunits that serve as referencestandards The standards of measurementused in science are those of theMetric Systemnamed as the International Systemof Units (SI), as of 1960 It has simplicity, and is based on10 or multiples of 10 7 base units, but only fivecommonly used in chemistry: meter,kilogram, kelvin, second, and mole.3334The Fundamental SI UnitsNature of Measurements(Le Système International, SI)Physical eratureKelvinKTimeSecondsMolemolMassAmount of substance Luminous intensityCandelacdAmpereAExamples: 20 grams 6.63 x 10-34 Joule secondsNot commonly used in chemistry:Electric currentMeasurement - quantitative observationconsisting of 2 parts:parts: Part 1 number Part 2 - scale (unit)3536

LengthInternational System of Units In SI, the basic unit of length is Sometimes, non-SI units are usedLiter, Celsius, calorie Some are derived units They are made by joining other units Speed miles/hour (distance/time) Density grams/mL (mass/volume) the meter (m) Length is the distancebetween two objects measured with ruler We make use of prefixes forunits larger or smaller37SI Prefixes Page 74Common to ChemistryPrefix38VolumeUnitMeaning ExponentAbbreviation The space occupied by any sampleof matter. Calculated for a solid by multiplyingthe length x width x height; thusderived from units of redth10-2 SI unit Milli-mthousandth10Micro-millionth10-6 Everyday unit Liter (L), which is Nano-nbillionth10-3non-SI.cubic meter (m3)(Note: 1mL 1cm3)-93940The Volume Changes!Devices for Measuring LiquidVolume Volumes of a solid, liquid, or gas Graduated cylinders Pipets Burets Volumetric Flasks Syringes41will generally increase withtemperature Much more prominent for GASES Therefore, measuringinstruments are calibrated for aspecific temperature, usually 20oC, which is about roomtemperature42

Units of MassWorking with Mass Mass is a measure of the The SI unit of mass is thequantity of matter present Weight is a force thatmeasures the pull by gravity- itchanges with location Mass is constant, regardless oflocationkilogram (kg), even though amore convenient everydayunit is the gram Measuring instrument is thebalance scale4344Units of TemperatureTemperature is a measure of howwithhot or cold an object is. (Measureda thermometer.) Heat moves from the object at thehigher temperature to the object atthe lower temperature. We use two units of temperature: Celsius Kelvin named after Anders Celsius named after Lord Kelvin45- Page 7847

Section 3.3Conversion ProblemsUnits of Energy Conversions between joulesand calories can be carriedout by using the followingrelationship: OBJECTIVE: Constructconversion factorsfrom equivalentmeasurements.1 cal 4.184 J4950Section 3.3Conversion Problems Section 3.3Conversion ProblemsOBJECTIVE: ApplyOBJECTIVE: Solvethe techniques ofdimensional analysis to avariety of conversionproblems.problems by breakingthe solution into steps.51Section 3.3Conversion Problems 52Conversion factors OBJECTIVE: Convertcomplex units, usingdimensional analysis. 53A ratio of equivalent measurementsStart with two things that are the same:one meter is one hundred centimeterswrite it as an equation1 m 100 cmWe can divide on each side of theequation to come up with two ways ofwriting the number 1 54

Conversion factors1m100 cm Conversion factors100 cm100 cm1m100 cm 155Conversion factors1m100 cm1m1m 56Conversion factors1m100 cm1100 cm1m1 1100 cm1m57Conversion factors A unique way of writing the number 1In the same system they are definedquantities so they have an unlimitednumber of significant figuresEquivalence statements always havethis relationship:big # small unit small # big unit1000 mm 1 m5958Practice by writing the twopossible conversion factors forthe following: Between kilograms andgrams between feet and inches using 1.096 qt. 1.00 L60

What are they good for?What are they good for?n We can multiply by a conversion factor tochange the units .n Problem: 13 inches is how many yards?n Known: 36 inches 1 yard.n 1 yard 136 inchesn 13 inches x1 yard 0.36 yards36 inchesWe can multiply by the number one creatively to change the units.Question: 13 inches is how manyyards?We know that 36 inches 1 yard.13 inches x1 yard 36 inches6162Conversion factorsCalled conversion factorsbecause they allow us toconvert units. really just multiplying byone, in a creative way. 63Dimensional Analysis Converting Between UnitsDimensional Analysis provides analternative approach to problem solving,instead of with an equation or algebra.A ruler is 12.0 inches long. How long isit in cm? ( 1 inch 2.54 cm)How long is this in meters?A race is 10.0 km long. How far is this inmiles, if: 1 mile 1760 yards1 meter 1.094 yards65 Problems in which measurements withone unit are converted to an equivalentmeasurement with another unit areeasily solved using dimensionalanalysisSample: Express 750 dg in grams.Many complex problems are bestsolved by breaking the problem intomanageable parts.66

- Page 86Section 3.4Density OBJECTIVES: Calculatethe density of amaterial from experimentaldata.69DensitySection 3.4Density 70 Which is heavier- a pound of leador a pound of feathers? Most people will answer lead, butthe weight is exactly the same They are normally thinking aboutequal volumes of the two The relationship here betweenmass and volume is called DensityOBJECTIVES: Describehow densityvaries with temperature.7172

Density- Page 90Note temperature and density units The formula for density is:massvolume Common units are: g/mL, orpossibly g/cm3, (or g/L for gas) Density is a physical property, anddoes not depend upon sample sizeDensity 7374Density and WaterDensity and Temperature Water is an important exception to What happens to the density as thetemperature of an object increases? Mass remains the same Most substances increase in volumeas temperature increases Thus, density generally decreasesas the temperature increasesthe previous statement. Over certain temperatures, thevolume of water increases as thetemperature decreases (Do youwant your water pipes to freeze inthe winter?) Does ice float in liquid water? Why?7576- Page 92- Page 917778

2. Exactly defined quantities b) 60 minutes 1 hour 18 Sig Fig Practice #1 How many significant figures in the following? 1.0070 m 5 sig figs 17.10 kg 4 sig figs 100,890 L 5 sig figs 3.29 x 103 s 3 sig figs 0.0054 cm 2 sig figs 3,200,000 2 sig figs 5 dogs unlimited These come f

Related Documents:

Part One: Heir of Ash Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Chapter 25 Chapter 26 Chapter 27 Chapter 28 Chapter 29 Chapter 30 .

TO KILL A MOCKINGBIRD. Contents Dedication Epigraph Part One Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Part Two Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18. Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Chapter 25 Chapter 26

DEDICATION PART ONE Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 PART TWO Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 .

About the husband’s secret. Dedication Epigraph Pandora Monday Chapter One Chapter Two Chapter Three Chapter Four Chapter Five Tuesday Chapter Six Chapter Seven. Chapter Eight Chapter Nine Chapter Ten Chapter Eleven Chapter Twelve Chapter Thirteen Chapter Fourteen Chapter Fifteen Chapter Sixteen Chapter Seventeen Chapter Eighteen

18.4 35 18.5 35 I Solutions to Applying the Concepts Questions II Answers to End-of-chapter Conceptual Questions Chapter 1 37 Chapter 2 38 Chapter 3 39 Chapter 4 40 Chapter 5 43 Chapter 6 45 Chapter 7 46 Chapter 8 47 Chapter 9 50 Chapter 10 52 Chapter 11 55 Chapter 12 56 Chapter 13 57 Chapter 14 61 Chapter 15 62 Chapter 16 63 Chapter 17 65 .

HUNTER. Special thanks to Kate Cary. Contents Cover Title Page Prologue Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter

Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 . Within was a room as familiar to her as her home back in Oparium. A large desk was situated i

The Hunger Games Book 2 Suzanne Collins Table of Contents PART 1 – THE SPARK Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8. Chapter 9 PART 2 – THE QUELL Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapt