AP ChemistryAP ChemistryOlympic High SchoolOlympic High School

Mr. DanielMr. Daniel

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The Scientific MethodThe Scientific Method

Hypothesis: a tentative explanation or prediction based on experimental observations

Law: a description of observed natural phenomena

Theory: a unifying principle that explains a body of facts and the laws based on them. A good theory can be modified to explain new information.

What is chemistry?What is chemistry?

“Science that deals with the properties, composition, and structure of substances (elements and compounds), the reactions and transformations they undergo, and the energy released or absorbed during those processes... Often called the "central science," chemistry is concerned with atoms as building blocks..., with everything in the material world, and with all living things.” Encyclopaedia Britannica, 2002.

“The study of the properties of materials and the changes that materials undergo.” Chemistry: The Central Science, Brown, LeMay, Bursten 7th ed.

Why should we study chemistry Why should we study chemistry / How does chemistry affect us?/ How does chemistry affect us?

Food science

Forensics chemistry

Drugs

Environmental chemistry: geo- and atmospheric

Materials (construction materials, clothing, paints, computer components, etc)

New energy sources

Et cetera...

Classification & Properties of MatterClassification & Properties of Matter

Matter – Anything that occupies space and has mass.

Substance – Pure matter with unique properties; it cannot be separated by physical processes.

Element – Cannot be subdivided by chemical or physical processes into simpler substances.

Atom – The smallest particle of an element that retains the characteristic chemical properties of that element.

CompoundsCompounds

Compounds – Contains more than one type of atom, but all molecules (or repeat units) are the same, e.g., water (H2O), sodium chloride (NaCl), and “fool’s gold” pyrite (FeS2).

Chemical formula – gives the ratio of atoms of each element in a compound.

Molecule – smallest discrete units that retain the composition and chemical characteristics of the compound. These groups of atoms are held together with covalent bonding

MixturesMixtures

Mixture – Have variable composition and can be separated into component parts by physical methods. Mixtures contain more than one kind of molecule, and their properties depend on the relative amount of each component present in the mixture.

Homogeneous Mixture (solution) – Uniform composition. Air: principle components include O2, N2 & CO2 Brass: solid solution of Cu and Zn

Heterogeneous Mixture – Non-uniform composition. Chocolate Chip Cookie: Chocolate, flour, water, etc Blood– red & white blood cells, plasma, etc.

Ne N2

SO3 Homogeneous Mixture

Physical PropertiesPhysical Properties

Physical Properties: Properties that can be observed and measured without changing the composition of a substance.

color, state of matter, melting and boiling points

density, solubility, electric conductivity,

malleability and ductility, viscosity, etc...

Extensive Properties: Depends on the amount of a substance present, e.g., mass and volume.Intensive Properties: Does not depend on the amount of a substance present, e.g., boiling point and density.

States of MatterStates of Matter

• Gas: volume varies with temperature & pressure; no definite shape; gas molecules are far apart.

• Solid: fixed volume; rigid shape; particles are packed closely together.

• Liquid: fixed volume; no definite shape; atoms or molecules are arranged randomly

Chemical PropertiesChemical Properties

Chemical Properties: Describe the way a substance may change or react to form other substances. Examples include:

Ethanol burns in air (reacts with oxygen in the air)

Sodium reacts vigorously with water

Corrosion of metal parts (rust)

Etc.

Chemical ChangeChemical Change

2H2(g) + O2(g) 2H2O(g)

SI (Metric) UnitsSI (Metric) Units

Measured PropertyMeasured Property Name of UnitName of Unit AbbreviationAbbreviation

MassMass kilogram (not gram!)kilogram (not gram!) kgkg

LengthLength metermeter mm

TimeTime secondsecond ss

TemperatureTemperature kelvinkelvin KK

Amount of substanceAmount of substance molemole molmol

Electric currentElectric current ampereampere AA

Table 1.2 Some SI Base Units

Metric Prefixes (Table 1.3)Metric Prefixes (Table 1.3)

PrefixPrefix AbbreviationAbbreviation MeaningMeaning ExampleExample

mega-mega- MM 101066 1 megaton = 11 megaton = 1××101066 tons tons

kilo-kilo- kk 101033 1 kilogram (kg)= 11 kilogram (kg)= 1××101033 grams grams

deci-deci- dd 1010-1-1 1 decimeter (dm) = 11 decimeter (dm) = 1××1010-1-1 m m

centi-centi- cc 1010-2-2 1 centimeter (cm) = 11 centimeter (cm) = 1××1010-2-2 m m

milli-milli- mm 1010-3-3 1 millimeter (mm) = 11 millimeter (mm) = 1××1010-3 -3 mm

micro-micro- 1010-6-6 1 micrometer (1 micrometer (m) = 1m) = 1××1010-6-6 m m

nano-nano- nn 1010-9-9 1 nanometer (nm) = 11 nanometer (nm) = 1××1010-9-9 m m

pico-pico- pp 1010-12-12 1 picometer (pm) = 11 picometer (pm) = 1××1010-12-12 m m

femto-femto- ff 1010-15-15 1 femtometer (fm) = 11 femtometer (fm) = 1××1010-15-15 m m

TemperatureTemperature

Fahrenheit scale Celsius scale

water freezes 32 °F 0 °C

body temperature 98.6 °F 37 °C

water boils 212 °F 100 °C

T (°C) = 5 °C / 9 °F [ T(°F) – 32]

Kelvin scale = same size unit as Celsius, but the lowest temperature that can be achieved is absolute zero

K = °C +273 °C = K - 273

What about Volume?What about Volume?

1 m3 = 1000 dm3 (L)

= 1,000,000 cm3

1,000,000 cm3 = 1 106 cm3

Liter (L) is not a base SI unit.

It is a derived unit.

DensityDensityDensity = Mass

Volume

Units used are : g/mL (liquids), g/cm3 (solids), g/L (gases)

Precision and AccuracyPrecision and Accuracy

Significant Figures!!Significant Figures!!

Significant FigureSignificant Figure

• Significant figures are a scientist’s way of Significant figures are a scientist’s way of reporting on how accurately a measurement reporting on how accurately a measurement was made.was made.

• Accuracy depend on two things:Accuracy depend on two things:• The device used to measureThe device used to measure• The care taken by the individualThe care taken by the individual

Significant FiguresSignificant Figures

• A Significant figure is defined as including A Significant figure is defined as including all certain digits plus one estimated digit.all certain digits plus one estimated digit.

What would be the measurement of the liquid in the graduated cylinder?

Significant Figures

Which measurement is the best?

What is the measured value?

What is the measured value?

What is the measured value?

Rules for Counting Significant Rules for Counting Significant FiguresFigures

Non-zerosNon-zeros alwaysalways count as significant count as significant figuresfigures::

3456 km 3456 km hashas

44 significant figuressignificant figures

Rules for Counting Significant Rules for Counting Significant FiguresFigures

ZerosZerosLeading zerosLeading zeros nevernever count as significant count as significant

figures:figures:

0.0486 mL 0.0486 mL hashas

3 3 significant figuressignificant figures

Rules for Counting Significant Rules for Counting Significant FiguresFigures

ZerosZerosCaptive zerosCaptive zeros alwaysalways count as count as

significant figures:significant figures:

16.07 cm 16.07 cm hashas

44 significant figures significant figures

Rules for Counting Significant Rules for Counting Significant FiguresFigures

ZerosZerosTrailing zerosTrailing zeros are significant only if the number are significant only if the number

contains a contains a written decimal pointwritten decimal point::

9.300 g 9.300 g hashas9300 g 9300 g has has 9300. g 9300. g hashas

4 significant figures4 significant figures

4 significant figures4 significant figures2 significant figures2 significant figures

Rules for Counting Significant Rules for Counting Significant FiguresFigures

Two special situations have an Two special situations have an unlimitedunlimited number number of significant figures:of significant figures:

1.1. Counted itemsCounted itemsa)a) 23 people, or 425 thumbtacks23 people, or 425 thumbtacks

2.2. ExactlyExactly defined quantities defined quantitiesb)b) 60 minutes = 1 hour60 minutes = 1 hour

Significant FiguresSignificant Figures

1. Read the number from left to right and count all the digits, starting with the first digit that is NOT zero if a decimal is present.

1200

1200.

1200.0

0.00120

0.01002

2 sig figs

4 sig figs

5 sig figs

3 sig figs

4 sig figs

Significant FiguresSignificant Figures

1) In multiplication or division, the number of significant figures in the answer should be the same as that in the quantity with the fewest significant figures.

0.080 × 125 =?

0.080 × 125 = 10 → 10. or 1.0 × 102

(2) (3) (answer should have 2 sig figs)

2) When the number is rounded off, the last digit to be retained is increased by one only if the following digit is 5 or greater.

Significant FiguresSignificant Figures3) When adding or subtracting numbers, the number of

decimal places in the answer is equal to the number of decimal places in the number with the fewest digits after the decimal.

10.1 + 100.001 + 1010 =?

10.1 (10-1 place)

100.001 (10-3 place)

1010. (100 place)

1120.101 → 1120. or 1.120×103

Dimensional AnalysisDimensional Analysis

(factor label method)

Use units to guide you through calculations.

Conversion factors are fractions where the numerator and denominator are the same quantity with different units. Many conversion factors are EXACT.

1000 mm 2.54 cm 1 ft 1 lb

1 m 1 in 12 in 453.6 g