Intro to Chemistry_Pre-AP

8/3/2019 Intro to Chemistry_Pre-AP

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Unit 1: Introduction to

ChemistryPre- AP Chemistry

Edmond NorthHigh School

Chapters: 1 & 2


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Scientific Method / Process

The Scientific Method is asystematic approach to problemsolving.

It is generally composed of thefollowing parts:

Question

HypothesisExperimentData AnalysisConclusion


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Measurement

Measurement: A quantitative observation consisting of anumeric value and units.Three are 2 kinds of units: base and derived

Base Units: Units are mutually independent of each otherEx: 7 meters, 30 kg, 6 seconds

Derived Units: Units are obtained mathematically from baseunits

Ex: 10 cm3, 0.9 g/mL, 22 meters/second


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Metric System

The Metric System is a decimalized system of measurement based on powers of 10

Used internationally and in the scientific communityConsists of base units and prefixes

The United States,Liberia, andMyanmar (Burma)are the only threecountries who donot use the metricsystem


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Metric System - Base Units

Mass

TimeTemperature

Volume

Distance

grams (g)

meters (m)

liters (L)

Kelvin (K) seconds (s)


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Accuracy & Precision

Accuracy: the degree of agreement between thetrue value and the

measured value(bullseye)Precision: the degree of agreement amongseveral measured values(grouping)


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Accuracy & Precision

Three different groups of students measure the mass of amedal, with a known value of 5.000 grams. Evaluateeach groups data for its accuracy and precision (low or

high):

Trial 1 5.003 g

Trial 2 5.002 g

Trial 3 5.001 g

Trial 1 5.400 g

Trial 2 5.202 g

Trial 3 5.905 g

Trial 1 5.503 g

Trial 2 5.499 g

Trial 3 5.501 g

Group 2 Group 1 Group 3

Accuracy ______ Precision ______



high high

low low high

low


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Uncertainty in Measurement

All measuring instrumentshave a degree of uncertainty .The more divisions a devicehas, the more accurate themeasurement.The last digit of a measurementis always estimated (uncertain).

How would you read thevolume in this graduatedcylinder if the markingsshowed every 5 mL instead of every 1 mL?

read from thebottom of themeniscus


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If we measure the length of the paw print with adecimeter ruler, we know for a certainty that it isbetween 0 and 1 decimeters. We estimate the nextdigit:

0.3 decimetersestimated digit


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If we measure the length of the paw print with acentimeter ruler, we know for a certainty that it isbetween 3 and 4 centimeters. We estimate thenext digit:

3.5 centimetersestimated digit


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If we measure the length of the paw print with amillimeter ruler, we know for a certainty that it isbetween 34 and 35 millimeters. We estimate thenext digit:

34.5 millimetersestimated digit


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Significant Figures

Significant Figures are the digits in a measurement that are knownwith some degree of certainty are called significant figures.

The number of significant figures in a measurement = the number of digits that are known + the estimated digitThe more significant figures after the decimal, the more accurate themeasurement.

Ex: This triple beambalance shows amass of 62.41grams. There are 4

significant figures inthis measurement.


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Significant Figure Rules

There are rules forcounting significantfigures related to:

Non-zero integersZeroes

Leading zeroesCaptive zeroes

Trailing zeroes


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Non-zero integers are always significant

3456 cm has4 sig figs


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Leading zeroes are never significant

0.0 486 g has3 sig figs


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Captive zeroes are always significant

16. 07 mL has4 sig figs


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Trailing zeroes are only significant if the numbercontains a decimal

9.3 0 m has

3 sig figs 93 0 m has2 sig figs


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Significant Figures Practice

How many significant figures are in the followingmeasurements?1. 8,675,309 km ____2. 90,210 L ____3. 0.07 mg ____4. 0.2020 daL ____

5. 300.00 g ____

7

414

5


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Scientific Notation Rules

CoefficientsCoefficients must be greater than or equal to 1 and less than 10Coefficients can be positive or negativeAll numbers in the coefficient are counted as significant

Which of the following numbers are writtenincorrectly?

22 x 10 5 9.5 x 10 2 10 x 10 8

7 x 10 -3 0.3 x 10 -9 -1.00 x 10 6


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Scientific Notation RulesBases

Base is always a 10Bases are never counted as significant

ExponentsExponents are always integersExponents can be positive (big number) or negative (small number)

Ex: 1 x 103 = 1000 and 1 x 10-3 = 0.001Exponents are never counted as significant

Which of the following numbers are written incorrectly?

4.1 x 10 -5 2.2 x 6 20 1.0 x 10 -1

7 x 10 0 0.15 x 10 -9 -7 x 10 6.3


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Scientific Notation

How to enter the number 2.5 x10 -8 into the calculator:

Enter the coefficient 2.5

Press 2nd, then EE

Enter the exponent -8

It should appear on yourscreen as 2.5E-8


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Significant Figure OperationsMultiplication & Division

Calculate raw answer Rounded answer must contain no more significant figures than themeasurement with the least number of significant figures

Example: What is the density of a bar of gold with a mass of 87.82 g anda volume of 4.55 cm 3? (Density = mass volume)

87.82 g 4.55 cm 3 = 19.301099 g/cm 3 19.3 g/cm 3

4 sig figs 3 sig figs raw answer 3 sig figs


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Significant Figure Operations

Addition & SubtractionCalculate raw answer Rounded answer can have no more digits to the right of the decimalpoint than the measurement with the least number of digits to theright of the decimal point

Example: What is the difference in length between a professional shotput throw of 23.125 meters and an amateur shot put throw of 21.2meters?

23.125 m 21.2 m = 1.925 m 1.9 m3 digits 1 digit raw 1 digit

after decimal after decimal answer after decimal


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Exact Numbers

Exact Numbers are differentfrom measurements becausethey have no uncertaintySignificant figures does notapplyExamples

Conversions (3 feet = 1 yard)Counting Numbers (20 M&Ms)


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Metric System - PrefixesPrefix Symbol Numeric Representation

tera- T 10 12 1,000,000,000,000

giga- G 10 9 1,000,000,000

mega- M 10 6 1,000,000

kilo- k 10 3 1,000hecto- h 10 2 100

deka- da 10 1 10

(base unit) (none) 10 0 1

deci- d 10 -1 0.1

centi- c 10 -2 0.01

milli- m 10 -3 0.001

micro- 10 -6 0.000001

nano- n 10 -9 0.000000001

pico- p 10 -12 0.000000000001


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Powers of Ten


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Remember

K ing H enry d ied by drinkingchocolate m ilk.

Kilo Hecto Deka Base Deci, Centi,and Milli.


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Metric Conversions

Example: How many kilograms are in 75decigrams?

Example: How centiliters are in 12 dekaliters?

Move decimal 4 places to the left: 75 dg = 0.0075 kg

Move decimal 3 places to the right: 12 daL = 12,000 cL

(start)

k h da d c m base x x


(start)


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Metric Conversions Practice

Practice metric conversions:

1. _______ dg = 4.2 hg2. _______ dam = 6,055 mm3. _______ L = 1 cL

4. _______ cK = 0.003 kK5. _______ s = 11,700,000 s


4,2000.6055

0.01

30011.7


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Metric System: Pressure

Pressure is the force over a given areaIf someone stepped on your foot, which shoe would you preferthey wore?

Pressure is measured in units of:1 Atmospheres (atm)101.3 kiloPascals (N/m 2)760 mmHg (mm of Mercury)

760 torrsPressure is measured by 2 instruments:

BarometerManometer


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Pressure Conversions

400 torr = __________ kPa400 torr 101.3kPa = 53.32kPa

760 torr

328 mmHg = __________ atm328mmHg 1atm = 0.432atm

760 mmHg

1 atm = 760 torr = 760 mmHg = 101.3 kPa


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Density

Density is the ratio of anobjects mass and volume

The formula for density is D =

m / vIn chemistry, the 2 mostcommon units of density willbe g/mL and g/cm 3

The four cubes to the right havethe same volume (1 cm 3), butdifferent masses. How does this

effect their densities?


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Density

The density of an object is an intensivephysical property , meaning it cannot bechanged no matter the quantity

A property that changes with the amount or quantity of thesubstance is an extensive property.

The density of water is 1 g/mLObjects that float < 1 g/mLObjects that sink > 1 g/mL

What happens to the density of an objectwhen it is sawed I half?


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The Mole

In the same way a dozen is worth 12,a mole is worth 6.02 x 10 23

This number is called Avogadrosnumber

Mole is abbreviated as mol

Written in expanded form, thatnumber is:602,000,000,000,000,000,000,000

The mole is a large number becauseparticles are so small, it takes manyof them make up an amount we cansee and understand

We can use it to count anything!


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The Mole

1 dozen cookies = 12 cookies1 mole of cookies = 6.02 X 10 23 cookies

1 gross cars = 144 cars1 mole of cars = 6.02 X 10 23 cars

1 ream Al particles = 500 Al particles1 mole of Al particles = 6.02 X 10 23 particles


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Mole Calculations

6.02 x 10 23 particles = 1 mole

Ex: How many particles are in 3.00 moles of N 2?3.00 mol N 2 6.02 x 10 23 particles =

1 mol N 2Ex: How many moles of Na are in 1.10 x 10 23 particles?

1.10 x 10 23 particles Na 1 mol Na =6.02 x 10 23 particles Na

1.81 x 10 24 particles

1.83 x 10 22 moles


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2 Unit Conversions

Convert the density of titanium (4.54g/mL) tokg/L.

Convert 13.2 mg/mL to g/cm 3.


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Classifying Matter


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Pure Substances

Pure substances cannot be separated by physicalmeans

Elements: cannot be chemically separated, listed on the periodic table

Compounds: can be chemically separated, made up of elements

carbon (C) sulfur (S) copper (Cu) mercury (Hg)

salt (NaCl) water (H 2O) sugar (C 6H12O6) rust (Fe 2O3)


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Pure Substances

Particle representations of Elements

Compounds


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Periodic Table

Each square on the periodictable contains:Name of Element

SymbolFirst letter is upper case, secondletter must be lower case

Atomic MassNumber (usually with a decimal)indicates the mass (g) of 1 mole of that element

Atomic Number


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Types of Elements


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Period/Series


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The Mole


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Molar Mass of Atoms

How do chemists count Avogadros number? By measuring mass (just like how they countaluminum cans for recycling)

The mass (think grams) of one mole of a substance

Atomic masses are based on the mass of carbonOne mole of carbon contains 6.02 x 1023 atoms of C

1 carbon atom is 12.011 amu

1 mole of carbon is 12.011 grams


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Molar Mass of Atoms

The mass of 1 mole (in grams)Equal to the numerical value of the average

atomic mass (get from periodic table)Examples:

1 mole of C atoms = 12.0 g

1 mole of Mg atoms = 24.3 g1 mole of Cu atoms = 63.5 g


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Practice

Find the molar mass1 mole of Au atoms =

1 mole of Sn atoms =


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Chemical Formulas

The chemical formula describes a compoundusing numbers and element symbols

Subscript s denote number of each element in a compoundEx: H

2O has 2 hydrogens and 1 oxygen

Ex: Al 2(SO 4)3 has 2 aluminums, 3 sulfurs, and 12 oxygens

Coefficients act as a scalar (also called a multiplier)Ex: 6H 2O has 12 hydrogens and 6 oxygensEx: 3Al 2(SO 4)3 has 6 aluminums, 9 sulfurs, and 36 oxygens


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Binary Ionic Compounds

A Binary Ionic Compound contains 2 elements:metal & nonmetalWhen you write a formula, you add subscripts tothe symbols for the ions until the algebraic sum of the ions charges is zero.Naming:

Name the metalDrop the end of nonmetal and add ide

Example: MgCl 2 = magnesium chloride


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Diatomic Elements

Some elements are always found as a pair(2 together)

H2, O 2, N 2, F2, Cl 2, Br 2, I2Try to remember HOF BrINCl

Example:How many atoms of O are present in 78.1 g of oxygen?

Practice:How many grams of Cl are present in 100 atoms of chlorine?

78.1 g O 2 = Xg32.0 g O 2 2(6.02 X 10 23 atoms O)


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Classifying Matter


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Mixtures

Mixtures are composed of two or more substancesthat can be separated by physical means; containselements and/or compounds

Heterogeneous Mixtures : not uniform throughoutHomogeneous Mixtures: uniform throughout

Particle representations of mixtures


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Heterogeneous Mixtures

HeterogeneousMixture: two or more

substancesphysically combined;not uniformthroughoutEx: Granite, chexmix


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Suspensions

A suspension is aheterogeneous fluidcontaining solid particles

that are sufficiently largefor sedimentation.The internal phase (solid)is dispersed throughoutthe external phase (fluid)through mechanical

Suspensions willeventually settle.


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Homogeneous Mixtures

Homogeneous Mixture:two or more substances

physically combined;uniform throughoutKnow as a solution composed of

Solute: substance being dissolved(smaller amount)

Solvent: substance that does thedissolving (larger amount)

Examples: kool-aid, brass


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Separating a Mixture

Separating a mixture -components are separatedwithout changing their physical

identity


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Magnetism

Separates metals (such asiron) from a mixture


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Filtration

Separates solid substancesfrom liquids and solutions


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Evaporation

Separates a dissolvedsolid from its solvent


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Distillation

Separates homogeneousmixture with differentboiling points (heat

mixture and catchcondensed vapor)


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Centrifuging

Separates heavierparticles (bottom of tube)from lighter particles (top

of tube) by spinningthem at high speeds


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Chromatography

Separates substances on the basis of their differences insolubility in a solvent - different substances areattracted to paper or gel and move at different speeds


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Properties of Matter

A property is a characteristic that describe matteror how it behavesPhysical determined without a chemical change

Extensive vary with amount of matter (Ex. Mass, volume, length, area)Intensive does not vary with amount (Ex. Density, color, odor, melting point, solubility)

Chemical can only be determined by a chemical

changeEx. Flammability, reactivity with acid, stability of a compound (how easily itdecomposes)


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Changes of Matter

Physical Changes do not involve a change inchemical identity

Ex: boiling, freezing, melting, dissolving, evaporating, and crystallizing
http://images.google.com/imgres?imgurl=http://www.iamtonyang.com/0411/boiling_water.jpg&imgrefurl=http://www.tlhines.com/blog/2005_04.php&h=480&w=640&sz=82&hl=en&start=13&usg=__5ihCVULSr8HORAl9faRZZTNz2kk=&tbnid=gSv9fSHKHnBC7M:&tbnh=103&tbnw=137&prev=/images?q=boiling&gbv=2&hl=enhttp://en.wikipedia.org/wiki/Image:Sugar_2xmacro.jpghttp://images.google.com/imgres?imgurl=http://www.bu.edu/sjmag/news-cms/photos/420IceCubeEarth.jpg&imgrefurl=http://www.bu.edu/phpbin/news-cms/news/?dept=1127&id=47227&template=228&h=282&w=420&sz=117&hl=en&start=17&usg=__vT1cywjrGcqaA1nSOe47hL8Ty_M=&tbnid=JjR9Pq9psnVHFM:&tbnh=84&tbnw=125&prev=/images?q=ice+water&gbv=2&hl=en


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Changes of Matter

Chemical Changes newsubstances are formed inthe reaction

Ex: iron rusting, copperoxidizing, wood burning,silver tarnishing
http://images.google.com/imgres?imgurl=http://www.learner.org/channel/courses/essential/physicalsci/images/s4.rusty_nail.jpg&imgrefurl=http://www.learner.org/channel/courses/essential/physicalsci/session4/closer1.html&h=300&w=300&sz=34&hl=en&start=1&usg=__pHUV6xZ128_RBS1zA2664AQQ1ak=&tbnid=ZHnprrbo0b7rgM:&tbnh=116&tbnw=116&prev=/images?q=rusty+nail&gbv=2&hl=en


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Evidence for Changes of Matter

Color ChangeGas produced

without heatingPrecipitate formedNew odor develops

Large amount of heator light produced
http://images.google.com/imgres?imgurl=http://www.popsci.com/files/imagecache/photogallery_image/files/articles/salt_ss_fire2.jpg&imgrefurl=http://www.popsci.com/diy/gallery/2006-10/making-salt-hard-way&h=340&w=440&sz=31&hl=en&start=26&usg=__QWTVueELH4iukDKbJHITGgw848g=&tbnid=rF9IF9RY8XrAaM:&tbnh=98&tbnw=127&prev=/images?q=sodium+fire&start=18&gbv=2&ndsp=18&hl=en&sa=Nhttp://images.google.com/imgres?imgurl=http://www.powerlabs.org/images/ln2dem3.jpg&imgrefurl=http://www.powerlabs.org/ln2demo.htm&h=292&w=300&sz=13&hl=en&start=16&usg=__0FY2KGjpxBujASqe9iB4WddgJww=&tbnid=ErTXpg9dFXLePM:&tbnh=113&tbnw=116&prev=/images?q=gas+balloon+flask&gbv=2&hl=en


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Law of Conservation of Mass

The LCM says matter is neither created nordestroyed during a chemical change

The mass of the reactants is always the same as the mass of the products.The number of atoms of each element is always the same in the reactants and the products.


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LCM Examples

Calcium chloride and sodium sulfate combine to formcalcium sulfate and sodium chloride.

CaCl 2 + Na 2SO 4 CaSO 4 + 2NaCl

Before and After:Does the mass change?


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Heat (Thermal) Energy

Heat is a form of energy that flows between twosamples of matter because of their difference intemperature

Heat flows from hot to coldIt can be absorbed or releasedMeasured in units of calories orJoules


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The End

Be Prepared for Unit 1 Test.

Intro to Chemistry_Pre-AP

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