Upload
jerome-lyons
View
221
Download
0
Tags:
Embed Size (px)
Citation preview
Unit 1: Introduction to Chemistry
Chemistry 1
Edmond North High School
Chapters: 1 & 2
Scientific Method / ProcessThe Scientific Method is a systematic
approach to problem solving.It is generally composed of the
following parts:QuestionHypothesisExperimentData AnalysisConclusion
Scientific Process
Question/Hypothesis
Experiment
Data AnalysisConclusion
Observation
MeasurementMeasurement: A quantitative observation consisting
of a numeric value and units.Three are 2 kinds of units: base and derived
Base Units: Units are mutually independent of each other Ex: 7 meters, 30 kg, 6 seconds
Derived Units: Units are obtained mathematically from base units Ex: 10 cm3, 0.9 g/mL, 22 meters/second
Metric SystemThe Metric System is a decimalized system of
measurement based on powers of 10Used internationally and in the scientific communityConsists of base units and prefixes
The United States, Liberia, and Myanmar (Burma) are the only three countries who do not use the metric system
Metric System - Base Units
Mass
TimeTemperature
Volume
Distance
grams (g)
meters (m)
liters (L)
Kelvin (K)seconds (s)
Accuracy & Precision
Accuracy: the degree of agreement between the true value and the measured value (bullseye)
Precision: the degree of agreement among several measured values (grouping)
Accuracy & PrecisionThree different groups of students measure the mass
of a medal, with a known value of 5.000 grams. Evaluate each group’s 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 2Group 1 Group 3
Accuracy ______Precision ______
Accuracy ______Precision ______
Accuracy ______Precision ______
high
high
low
low high
low
Uncertainty in MeasurementAll measuring instruments have
a degree of uncertainty. The more divisions a device has, the more accurate the measurement.
The last digit of a measurement is always estimated (uncertain).
How would you read the volume in this graduated cylinder if the markings showed every 5 mL instead of every 1 mL?
read from the bottom of the meniscus
Uncertainty in MeasurementIf we measure the length of the paw print with a
decimeter ruler, we know for a certainty that it is between 0 and 1 decimeters. We estimate the next digit:
0.3 decimetersestimated digit
Uncertainty in MeasurementIf we measure the length of the paw print with a
centimeter ruler, we know for a certainty that it is between 3 and 4 centimeters. We estimate the next digit:
3.5 centimetersestimated digit
Uncertainty in MeasurementIf we measure the length of the paw print with a
millimeter ruler, we know for a certainty that it is between 34 and 35 millimeters. We estimate the next digit:
34.5 millimetersestimated digit
Significant FiguresSignificant Figures are the digits in a measurement that
are known with 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 the measurement.
Ex: This triple beam balance shows a mass of 62.41 grams. There are 4 significant figures in this measurement.
Significant Figure Rules
There are rules for counting significant figures related to:Non-zero integersZeroes
Leading zeroes Captive zeroes Trailing zeroes
Significant Figure Rules
Non-zero integers are always significant
3456 cm has
4 sig figs
Significant Figure Rules
Leading zeroes are never significant
0.0486 g has
3 sig figs
Significant Figure Rules
Captive zeroes are always significant
16.07 mL has
4 sig figs
Significant Figure Rules
Trailing zeroes are only significant if the number contains a decimal
9.30 m has
3 sig figs 930 m has
2 sig figs
Significant Figures Practice How many significant figures are in the following
measurements?
1. 8,675,309 km ____
2. 90,210 L ____
3. 0.07 mg ____
4. 0.2020 daL ____
5. 300.00 g ____
7
4
14
5
Significant Figure OperationsMultiplication & Division
Calculate “raw” answerRounded answer must contain no more significant
figures than the measurement with the least number of significant figures
Example: What is the density of a bar of gold with a mass of 87.82 g and a volume of 4.55 cm3? (Density = mass volume)
87.82 g 4.55 cm3 = 19.301099 g/cm3 19.3 g/cm3
4 sig figs 3 sig figs raw answer 3 sig figs
Significant Figure OperationsAddition & Subtraction
Calculate “raw” answerRounded answer can have no more digits to the right of
the decimal point than the measurement with the least number of digits to the right of the decimal point
Example: What is the difference in length between a professional shot put throw of 23.125 meters and an amateur shot put throw of 21.2 meters?
23.125 m 21.2 m = 1.925 m 1.9 m 3 digits 1 digit raw 1 digit
after decimal after decimal answer after decimal
Exact NumbersExact Numbers are different from
measurements because they have no uncertainty
Significant figures does not applyExamples
Conversions (3 feet = 1 yard)Counting Numbers (20 M&Ms)
Metric System - Base Units
Mass
TimeTemperature
Volume
Distance
grams (g)
meters (m)
liters (L)
Kelvin (K)seconds (s)
Metric System - PrefixesPrefix Symbol Numeric Representation
tera- T 1012 1,000,000,000,000
giga- G 109 1,000,000,000
mega- M 106 1,000,000
kilo- k 103 1,000
hecto- h 102 100
deka- da 101 10
(base unit) (none) 100 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
Powers of Ten
From Quarks to Outer Space
Metric ConversionsExample: How many kilograms are in 75 decigrams?
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
k h da d c m base x x
(start)
Metric Conversions Practice
Practice metric conversions:
1. _______ dg = 4.2 hg2. _______ dam = 6,055 mm3. _______ L = 1 cL4. _______ cK = 0.003 kK5. _______ s = 11,700,000 s
k h da d c m base x x
4,2000.6055
0.0130011.7
Remember
King Henry died by drinking chocolate milk.
Kilo Hecto Deka Base Deci, Centi, and Milli.
DensityDensity is the ratio of an
object’s mass and volumeThe formula for density is D =
m / vIn chemistry, the 2 most
common units of density will be g/mL and g/cm3
The four cubes to the right have the same volume (1 cm3), but different masses. How does this effect their densities?
DensityThe density of an object is an intensive physical
property, meaning it cannot be changed no matter the quantity.If the property changes with the amount of substance
present then it is an extensive property.The density of water is 1 g/mL
Objects that float < 1 g/mLObjects that sink > 1 g/mL
What happens to the density of an object when it is sawed I half?
Counting MatterWhat are some common ways we
count matter?
Dozen = 12
Ream = 500
Gross = 144
Mole = 6.02 x 1023
The MoleIn the same way a dozen is worth 12,
a mole is worth 6.02 x 1023
This number is called Avogadro’s number
Mole is abbreviated as “mol”Written in expanded form, that
number is: 602,000,000,000,000,000,000,000The mole is a large number because
particles are so small, it takes many of them make up an amount we can see and understand
We can use it to count anything!
1 dozen cookies = 12 cookies1 mole of cookies = 6.02 X 1023 cookies
1 gross cars = 144 cars1 mole of cars = 6.02 X 1023 cars
1 ream Al particles = 500 Al particles1 mole of Al particles = 6.02 X 1023 particles
The Mole
Scientific NotationScientific Notation is mathematical shorthand that
makes large and small numbers manageableIt is composed of three parts:
CoefficientBaseExponent
4.56 x 10-7Coefficient Base
Exponent
Scientific Notation RulesCoefficients
Coefficients must be greater than or equal to 1 and less than 10
Coefficients can be positive or negativeAll numbers in the coefficient are counted as significant
Which of the following numbers are written incorrectly?
22 x 105 9.5 x 102 10 x 108
7 x 10-3 0.3 x 10-9 -1.00 x 106
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 620 1.0 x 10-1
7 x 100 0.15 x 10-9 -7 x 106.3
Scientific NotationHow to enter the number 2.5 x 10-8
into the calculator:Enter the coefficient 2.5
Press 2nd, then EE
Enter the exponent -8
It should appear on your screen as 2.5E-8
Mole Calculations6.02 x 1023 particles = 1 mole
Ex: How many particles are in 3.00 moles of N2?
3.00 mol N2 6.02 x 1023 particles =
1 mol N2
Ex: How many moles of Na are in 1.10 x 1023 particles?
1.10 x 1023 particles Na 1 mol Na =
6.02 x 1023 particles Na
1.81 x 1024 particles
1.83 x 1022 moles
Classifying Matter
Pure SubstancesPure substances cannot be separated by physical means
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 (H2O) sugar (C6H12O6) rust (Fe2O3)
Pure SubstancesParticle representations of…
Elements
Compounds
Periodic TableEach square on the
periodic table contains:Name of ElementSymbol
First letter is upper case, second letter must be lower case
Atomic Mass Number (usually with a
decimal) indicates the mass (g) of 1 mole of that element
Atomic Number
Types of Elements
Groups/Familes
Period/Series
The Mole
Molar Mass of AtomsHow do chemists “count” Avogadro’s number?By measuring mass (just like how they count
aluminum 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
Molar Mass of AtomsThe 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 g 1 mole of Cu atoms = 63.5 g
PracticeFind the molar mass
1 mole of Au atoms =
1 mole of Sn atoms =
Chemical Formulas• The chemical formula describes a compound using
numbers and element symbols– Subscripts denote number of each element in a
compound• Ex: H2O has 2 hydrogens and 1 oxygen
• Ex: Al2(SO4)3 has 2 aluminums, 3 sulfurs, and 12 oxygens
– Coefficients act as a scalar (also called a multiplier)• Ex: 6H2O has 12 hydrogens and 6 oxygens
• Ex: 3Al2(SO4)3 has 6 aluminums, 9 sulfurs, and 36 oxygens
Naming Covalent CompoundsTwo words, with prefixesPrefixes tell you how many.
mono, di, tri, tetra, penta, hexa, septa, nona, decaFirst element whole name with the appropriate prefix,
except monoSecond element, -ide ending with appropriate prefix
Naming Covalent CompoundsCO2
CO CCl4
N2O4
Diflourine monoxideNitrogen trichlorideDiphosphorus pentoxide
Three Types of Ionic Compounds (Salts)We will learn how to write formulas and
nomenclature (naming system) for:Binary Salts
2 elements: a metal and a nonmetalTernary Salts
3 or more elements Includes a polyatomic ion
Salts with Multiple Oxidation Numbers Can be binary or ternary Includes a transition metal
Binary Ionic CompoundsA Binary Ionic Compound contains 2 elements: metal &
nonmetalWhen you write a formula, you add subscripts to the 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: MgCl2 = magnesium chloride
Molar Mass of CompoundsThe Molar Mass of a compound is the mass in grams
of 1 mole equal to the sum of the atomic massesExample: What is the mass of 1 mole of CaCl2?
1 mole Ca x 40.1 g/mol = 40.1 g Ca2 moles Cl x 35.5 g/mol = + 71.0 g Cl
111.1 g/mol CaCl2
Practice
Prozac, C17H18F3NO, is a widely used anti-depressant that inhibits the uptake of serotonin by the brain. Find its molar mass.
Calculations with Molar Mass Examples
How many grams are in 2 moles of Cu?2 moles of Cu = Xg1 mole of Cu 63.546 g of Cu
How many moles are in 100 g of H2O?
100 g of H2O = Xg
18.015 g of H2O 1 mole of H2O
Practice
The artificial sweetener aspartame (C14H18N2O5), commonly known as Nutra-Sweet, is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?
Calculations with Particles/Mass
ExamplesHow many grams of CO2 are present in 3 particles of
CO2?
3 particles of CO2 = Xg
6.02 x 1023 particles of CO2 44.009 g of CO2
How many particles are present in 12.0 grams of NaCl?
12.0 g of NaCl = X particles
58.443 g of NaCl 6.02 x 1023 particles of NaCl
PracticeDiabetics do not properly
regulate insulin, which tells the body to take up glucose from the blood. What is the mass of 1.20 x 1024 molecules of glucose (C6H12O6)?
Diatomic ElementsSome elements are always found as a pair (2 together)
H2, O2, N2, F2, Cl2, Br2, I2
Try 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 O2 = Xg 32.0 g O2 2(6.02 X 1023 atoms O)
Classifying Matter
MixturesMixtures are composed of two or more substances
that can be separated by physical means; contains elements and/or compoundsHeterogeneous Mixtures: not uniform throughoutHomogeneous Mixtures: uniform throughout
Particle representations of mixtures…
Heterogeneous MixturesHeterogeneous Mixture:
two or more substances physically combined; not uniform throughout
Ex: Granite, chex mix
SuspensionsA suspension is a
heterogeneous fluid containing solid particles that are sufficiently large for sedimentation.
The internal phase (solid) is dispersed throughout the external phase (fluid) through mechanicalSuspensions will
eventually settle.
ColloidsColloids are suspensions of particles larger than
individual ions or molecules, but too small to be settled out by gravity.
ColloidsThe Tyndall Effect is
scattering of light particles used to determine whether something is a solution or suspension
Click image to play clip
Homogeneous MixturesHomogeneous Mixture:
two or more substances physically combined; uniform throughoutKnow as a solution
composed of… Solute: substance being
dissolved (smaller amount) Solvent: substance that
does the dissolving (larger amount)
Examples: kool-aid, brass
Separating a MixtureSeparating a mixture -
components are separated without changing their physical identityManual SeparationMagnetismFiltrationEvaporationDistillationCentrifugingChromatography
Manual Separation
DecantingSeparates two liquids of
different densities Sifting
Separates two solids of different particle size
by pouringSorting
Separates two solids by picking
MagnetismSeparates metals (such as
iron) from a mixture
FiltrationSeparates solid
substances from liquids and solutions
EvaporationSeparates a dissolved
solid from its solvent
DistillationSeparates homogeneous
mixture with different boiling points (heat mixture and catch condensed vapor)
CentrifugingSeparates heavier particles
(bottom of tube) from lighter particles (top of tube) by spinning them at high speeds
ChromatographySeparates substances on the basis of their
differences in solubility in a solvent - different substances are attracted to paper or gel and move at different speeds
Properties of MatterA property is a characteristic that describe matter or
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 change Ex. Flammability, reactivity with acid, stability of a
compound (how easily it decomposes)
EnergyEnergy is the ability to do workHeat: Energy used to cause the temperature of an
object to rise.Temperature - measure of the average kinetic energy
of the particlesWe measure temperature with a thermometer.
Heat (Thermal) EnergyHeat is a form of energy that flows between two
samples of matter because of their difference in temperatureHeat flows from hot to coldIt can be absorbed or releasedMeasured in units of calories orJoules
Changes of MatterPhysical Changes – do not involve a change in chemical
identityEx: boiling, freezing, melting, dissolving, evaporating, and
crystallizing
Changes of MatterChemical Changes –
new substances are formed in the reactionEx: iron rusting, copper
oxidizing, wood burning, silver tarnishing
Evidence for Changes of Matter
Color ChangeGas produced without
heatingPrecipitate formedNew odor developsLarge amount of heat or
light produced
The End of Unit 1.
Be Prepared for Test.