Chapter 1 Matter and Measurement. What is Chemistry? The study of all substances and the changes...

Chapter 1Chapter 1Matter and Matter and

MeasurementMeasurement

What is Chemistry?What is Chemistry?

The study of all substances and the The study of all substances and the changes that they can undergochanges that they can undergo

The CENTRAL SCIENCEThe CENTRAL SCIENCE

Why Study Chemistry?Why Study Chemistry?

Useful for other sciencesUseful for other sciences

Required course Required course Fun and ChallengingFun and Challenging

Remember:Remember:– Process of DiscoveryProcess of Discovery– Understand Concepts, NOT Single FactsUnderstand Concepts, NOT Single Facts

Scientific MethodScientific MethodObservatio

n

Question

Hypothesis

Experiment

Conclusion

Scientific MethodScientific Method

Natural Law

•Explains how nature behaves

Theory•Explains why nature behaves in a certain

way

Conclusion

Prediction Experiment

LiquidsLiquids

LiquidsLiquids

Definite Definite

Molecules Molecules

Not affected by Not affected by

SolidsSolids

SolidsSolids

Don’t Don’t

Definite Definite

Molecules Molecules

Not affected by Not affected by

GasesGases

Low Low

Density Density

Expands to Expands to

Indefinite Indefinite

Molecules move Molecules move

The Metric SystemThe Metric SystemThe International System of UnitsThe International System of Units

Standards of measurementStandards of measurementBase units (7) – Fig 1-14 p. 18Base units (7) – Fig 1-14 p. 18

1.1. MASS: MASS: 2.2. LENGTH: LENGTH: 3.3. TIME: TIME: 4.4. COUNT, QUANTITY: COUNT, QUANTITY: 5.5. TEMPERATURE: TEMPERATURE: 6.6. ELECTRIC CURRENT: ELECTRIC CURRENT: 7.7. LUMINOUS INTENSITY: LUMINOUS INTENSITY:

The Metric SystemThe Metric SystemDerived Units:Derived Units: AREA: AREA: VOLUME: VOLUME: ENERGY: ENERGY: FORCE: FORCE: PRESSURE:PRESSURE: POWER: POWER: VOLTAGE: VOLTAGE: FREQUENCY: FREQUENCY: ELECTRIC CHARGE: ELECTRIC CHARGE:

The Metric SystemThe Metric System

Metric Prefixes – make base unit larger Metric Prefixes – make base unit larger or smalleror smaller

Based on 10Based on 10

Math method vs. “Stairs”Math method vs. “Stairs”

Convert a volume of 12 microliters into Convert a volume of 12 microliters into centiliterscentiliters

Express a distance of 15 meters in Express a distance of 15 meters in kilometerskilometers

Convert 83 cm into metersConvert 83 cm into meters

Which is the longer amount of time, 1351 Which is the longer amount of time, 1351 ps or 1.2 ns?ps or 1.2 ns?

Convert 16 dL into LConvert 16 dL into L

Conversion PracticeConversion Practice

Types of MeasurementsTypes of Measurements

Mass – amount of Mass – amount of – Expressed in Expressed in – Does not Does not

Weight – Weight – – Expressed in Expressed in – Changes with Changes with

Types of MeasurementsTypes of Measurements

Volume – the amount of Volume – the amount of – – Many instruments to measureMany instruments to measure

Temperature – Temperature – – – Degrees Degrees – Degress Degress

DensityDensityCommon ratio used in Common ratio used in chemistrychemistry

Physical property of a Physical property of a substancesubstance

SI units: SI units:

SolidSolid–

LiquidLiquid–

GasGas–

Can change due to temperature and/or pressure changes

DensityDensity

1.Find the density of a piece of metal with a volume of 2.7 cm3 and a mass of 10.8 g.

2. Determine the mass of an object with a density of 0.24 g/cm3 and a volume of 2 cm3.

Uncertainty in MeasurementUncertainty in Measurement

Why are digits in measurements uncertain?Why are digits in measurements uncertain?

1.1. Instruments never completely free of flawsInstruments never completely free of flaws

2.2. Always involves estimationAlways involves estimation Choose the right instrument for the jobChoose the right instrument for the job May be estimated for you (electronic May be estimated for you (electronic

scales)scales) Scale is marked but you estimate the in-Scale is marked but you estimate the in-

betweenbetween

Uncertainty in MeasurementUncertainty in Measurement

Precision: Precision:

Accuracy: Accuracy:

Significant DigitsSignificant DigitsAll digits known with certainty plus one All digits known with certainty plus one final digit which is uncertain (or estimated)final digit which is uncertain (or estimated)

All non-zeros are All non-zeros are

A zero is significant when :A zero is significant when :– It is It is – It is It is

A zero is not significant when:A zero is not significant when:– It is It is – It is It is

Significant Digits - PRACTICESignificant Digits - PRACTICE

How many significant digits?How many significant digits?1.1. 54.2354.232.2. 23.0000523.000053.3. 0.00040.00044.4. 35000350005.5. 0.0005040.0005046.6. 45.62320045.6232007.7. 5,000,0005,000,0008.8. 4,000,000.14,000,000.1

Significant Digits - CalculationsSignificant Digits - Calculations

Addition and SubtractionAddition and Subtraction–

1.21 + 5.002 + 10. = 1.21 + 5.002 + 10. = 16.212 becomes 1616.212 becomes 16

34.5 + 12.45 + 23.0505 = 34.5 + 12.45 + 23.0505 =

186.31 + 11.1 = 186.31 + 11.1 =

12.0231 + 3.86 = 12.0231 + 3.86 =

0.100012 + 120. =0.100012 + 120. =

1200 + 12 + 15 + 0.5 =1200 + 12 + 15 + 0.5 =

Significant Digits - CalculationsSignificant Digits - Calculations

Multiplication and DivisionMultiplication and Division– The answer has as many sig figs as the The answer has as many sig figs as the

number with the fewest sig figsnumber with the fewest sig figs14.8 x 3.1 = 14.8 x 3.1 = 45.88 becomes 4645.88 becomes 46

18.2 x 3.0 =18.2 x 3.0 =

52/1.5 =52/1.5 =

321.868783 x 1 =321.868783 x 1 =

2400 x 2.123 =2400 x 2.123 =

15000/12.354 =15000/12.354 =

Scientific NotationScientific Notation

Convenient way of writing very large or Convenient way of writing very large or very small numbers and showing only very small numbers and showing only significant figuressignificant figuresNumber between 1 & 10 with a power of Number between 1 & 10 with a power of tenten5120 becomes 5.12 x 105120 becomes 5.12 x 1033

Move decimal point in original number to Move decimal point in original number to make number 1-10make number 1-10Move left = +; move right = -Move left = +; move right = -

Scientific Notation PracticeScientific Notation Practice

123,000 =123,000 =

0.000045 =0.000045 =

23.45 =23.45 =

0.0000000003 =0.0000000003 =

1,000,000 =1,000,000 =

Scientific NotationScientific Notation

Adding and subtractingAdding and subtracting

Multiply and divideMultiply and divide

3.38 x 103

Conversion FactorsConversion Factors

Enable movement between metric system and Enable movement between metric system and “English” system“English” system

See back cover of book and Appendix IIISee back cover of book and Appendix III

Common conversions you should memorizeCommon conversions you should memorize– 1 inch = 2.54 cm1 inch = 2.54 cm– 1 mile = 1.609 km1 mile = 1.609 km– 1 kg = 2.20 pounds1 kg = 2.20 pounds– 1 mL = 1 cm1 mL = 1 cm33

– 0 K = -273.15 0 K = -273.15 00CC– 00F = 1.8(F = 1.8(00C) + 32C) + 32

Dimensional AnalysisDimensional Analysis(Problem Solving)(Problem Solving)

Remember: ALWAYS use UNITS OF Remember: ALWAYS use UNITS OF MEASUREMENT in your work!!!MEASUREMENT in your work!!!

A technique of converting between unitsA technique of converting between units– Same system (metrics)Same system (metrics)– Different systems (inches to meters)Different systems (inches to meters)– Chemical equations….later chapters…Chemical equations….later chapters…

Dimensional AnalysisDimensional Analysis(Problem Solving)(Problem Solving)

Conversion Factors: ratio derived from the Conversion Factors: ratio derived from the equality between 2 different unitsequality between 2 different units

CF can be written either wayCF can be written either way

Dimensional AnalysisDimensional Analysis(Problem Solving)(Problem Solving)

The “t” methodThe “t” method

Example: How many liters are in 125.6 gallons?

Conversion Factor

How many seconds are in 4.15 hours?

Dimensional AnalysisDimensional Analysis(Problem Solving)(Problem Solving)

Dimensional AnalysisDimensional Analysis(Problem Solving)(Problem Solving)

If a student needs 1.5 mL of water, how many cups does he need?