copyright©2000 by houghton mifflin company. all rights reserved. 1 foundations of chemistry a quick...

Copyright©2000 by Houghton Mifflin Company. All rights reserved.

1

Foundations of Chemistry

A quick review!


2

Steps in the Scientific Method

1.1. ObservationsObservations

quantitativequantitative

qualitativequalitative

2.2. Formulating hypothesesFormulating hypotheses

possible explanation for the observationpossible explanation for the observation

3.3. Performing experimentsPerforming experiments

gathering new information to decidegathering new information to decide

whether the hypothesis is validwhether the hypothesis is valid


3

Outcomes Over the Long-Term

Theory (Model)Theory (Model)

A set of tested hypotheses that give anA set of tested hypotheses that give an overall explanation of some overall explanation of some

natural natural phenomenon.phenomenon.

Natural LawNatural Law

The same observation applies to manyThe same observation applies to many different systemsdifferent systems

Example - Law of Conservation of Example - Law of Conservation of MassMass


4

The Fundamental Steps of the Scientific

Method


5

The Various Parts of the Scientific

Method


6

Law v. Theory

A A lawlaw summarizes what happens; summarizes what happens;

A A theorytheory (model) is an attempt to (model) is an attempt to explain explain whywhy it happens. it happens.


7

Nature of Measurement

Measurement - quantitative observation consisting of Measurement - quantitative observation consisting of 2 parts2 parts

Part 1 - numberPart 1 - number Part 2 - scale (unit)Part 2 - scale (unit)

Examples:Examples:20 grams20 grams

6.63 6.63 Joule seconds Joule seconds


8

International System(le Système International)

Based on metric system and units Based on metric system and units derived from metric system.derived from metric system.


9

The Fundamental SI Units


10

Measurement of Volume


11

Common Types of Laboratory Equipment Used to Measure Liquid Volume


12

Measurement of Volume Using a BuretThe volume is read at the bottom of the liquid curve (called the meniscus).


13

Uncertainty in Measurement

A digit that must be A digit that must be estimatedestimated is called is called uncertainuncertain. A . A measurementmeasurement always has always has some degree of uncertainty.some degree of uncertainty.


14

Precision and Accuracy

Accuracy Accuracy refers to the agreement of a refers to the agreement of a particular value with theparticular value with the true true value.value.

PrecisionPrecision refers to the degree of agreement refers to the degree of agreement among several elements of the same among several elements of the same quantity.quantity.


15

The Difference between Precision and Accuracy


16

Types of Error

Random Error Random Error (Indeterminate Error) - (Indeterminate Error) - measurement has an equal probability of measurement has an equal probability of being high or low.being high or low.

Systematic Error Systematic Error (Determinate Error) - (Determinate Error) - Occurs in the Occurs in the same directionsame direction each time (high each time (high or low), often resulting from poor technique.or low), often resulting from poor technique.


17

Rules for Counting Significant Figures - Overview

1.1. Nonzero integersNonzero integers

2.2. ZerosZeros

leading zerosleading zeros

captive zeroscaptive zeros

trailing zerostrailing zeros

3.3. Exact numbersExact numbers


18

Rules for Counting Significant Figures - Details

Nonzero integersNonzero integers always count as always count as significant figures.significant figures.

3456 3456 has has

4 4 sig figs.sig figs.


19


ZerosZerosLeading zerosLeading zeros do not count as do not count as

significant figures.significant figures.

0.04860.0486 has has

33 sig figs. sig figs.


20


ZerosZeros Captive zerosCaptive zeros always count as always count as

significant figures.significant figures.

16.07 16.07 hashas

4 4 sig figs.sig figs.


21


ZerosZeros Trailing zerosTrailing zeros are significant only are significant only

if the number contains a decimal if the number contains a decimal point.point.

9.3009.300 has has

44 sig figs. sig figs.


22


Exact numbersExact numbers have an infinite number of have an infinite number of significant figures.significant figures.

11 inch = inch = 2.54 2.54 cm, exactlycm, exactly


23

Rules for Significant Figures in Mathematical Operations

Multiplication and Division: Multiplication and Division: # sig figs in # sig figs in the result equals the number in the least the result equals the number in the least precise measurement used in the calculation.precise measurement used in the calculation.

6.38 6.38 2.0 = 2.0 =

12.76 12.76 13 (2 sig figs)13 (2 sig figs)


24

Rules for Significant Figures in Mathematical Operations

Addition and Subtraction: Addition and Subtraction: # sig figs in the # sig figs in the result equals the number of decimal places result equals the number of decimal places in the least precise measurement.in the least precise measurement.

6.8 + 11.934 =6.8 + 11.934 =

22.4896 22.4896 22.5 (3 sig figs)22.5 (3 sig figs)


25

Dimensional Analysis

Proper use of “unit factors” leads to proper Proper use of “unit factors” leads to proper units in your answer.units in your answer.


26

Temperature

Celsius scale =Celsius scale =CCKelvin scale = KKelvin scale = K

Fahrenheit scale =Fahrenheit scale =FF


27

The Three Major Temperature

Scales


28

Normal Body Temperature on the Fahrenheit, Celsius,

and Kelvin Scales


29

Temperature


30

Density

Density Density is the mass of substance per unitis the mass of substance per unit

volume of the substance:volume of the substance:


31

Matter:Matter: Anything occupying Anything occupying

space and having mass.space and having mass.


32

Classification of Matter

Three States of Matter:Three States of Matter:

Solid: rigid - fixed volume and shapeSolid: rigid - fixed volume and shape

Liquid: definite volume but assumes the Liquid: definite volume but assumes the shape of its containershape of its container

Gas: no fixed volume or shape - assumes Gas: no fixed volume or shape - assumes the shape of its containerthe shape of its container


33

Types of Mixtures

Mixtures have variable composition.Mixtures have variable composition.

AA homogeneous mixturehomogeneous mixture is a solution (for is a solution (for example, vinegar)example, vinegar)

AA heterogeneous mixtureheterogeneous mixture is, to the naked is, to the naked eye, clearly not uniform (for example, a eye, clearly not uniform (for example, a bottle of ranch dressing)bottle of ranch dressing)


34

Pure Substances

Can be isolated by separation methods:Can be isolated by separation methods:

ChromatographyChromatography

FiltrationFiltration

DistillationDistillation


35

Simple Laboratory Distillation Apparatus


36

Element:Element: A substance that cannot be A substance that cannot be decomposed into simpler substances by decomposed into simpler substances by chemical means.chemical means.

Compound:Compound: A substance with a A substance with a constant composition that can be constant composition that can be broken down into elements by broken down into elements by chemical processes.chemical processes.


37

The Organization

of Matter


38

The Early History of ChemistryThe Early History of Chemistry

Before 16th CenturyAlchemy: Attempts (scientific or otherwise) to

change cheap metals into gold

17th CenturyRobert Boyle: First “chemist” to perform

quantitative experiments

18th CenturyGeorge Stahl: Phlogiston flows out of a burning

material.Joseph Priestley: Discovers oxygen gas,

“dephlogisticated air.”


39

Law of Conservation of MassLaw of Conservation of Mass

Discovered by Antoine Lavoisier

Mass is neither created nor destroyed

Combustion involves oxygen, not phlogiston


40

Other Fundamental Chemical LawsOther Fundamental Chemical Laws

A given compound always contains exactly the same proportion of elements by mass.

Carbon tetrachloride is always 1 atom carbon per 4 atoms chlorine.

Law of Definite Proportion


41

Other Fundamental Chemical LawsOther Fundamental Chemical Laws

When two elements form a series of compounds, the ratios of the masses of the second element that combine with 1 gram of the first element can always be reduced to small whole numbers.

The ratio of the masses of oxygen in H2O and H2O2 will be a small whole number (“2”).

Law of Multiple Proportions


42

Dalton’s Atomic Theory (1808)Dalton’s Atomic Theory (1808)

Each element is made up of tiny particles called atoms.

The atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways.


43

Dalton’s Atomic Theory(continued)

Dalton’s Atomic Theory(continued)

Chemical compounds are formed when atoms combine with each other. A given compound always has the same relative numbers and types of atoms.

Chemical reactions involve reorganization of the atoms - changes in the way they are bound together. The atoms themselves are not changed in a chemical reaction.


44

Representation of some of Gay-Lussac’s Experimental Results on Combining Gas Volumes


45

Representation of Combining Gases at the Molecular Level


46

Avogadro’s Hypothesis (1811)Avogadro’s Hypothesis (1811)

5 liters of oxygen

5 liters of nitrogen

Same number of particles!

At the same temperature and pressure, equal At the same temperature and pressure, equal volumes of different volumes of different gasesgases contain the same contain the same number of particles.number of particles.


47

Early Experiments to Characterize the AtomEarly Experiments to

Characterize the Atom

J. J. Thomson - postulated the existence of electrons using cathode ray tubes.

Ernest Rutherford - explained the nuclear atom, containing a dense nucleus with electrons traveling around the nucleus at a large distance.


48

Deflection of Cathode Rays by an Applied Electric Field


49

The Plum Pudding Model of the Atom


50

Diagram of the Millikan Apparatus


51

Rutherford’s Experiment on particle Bombardment of Metal Foil


52

Expected and Actual Results of Rutherford’s Experiment


53

The Modern View of Atomic Structure

The Modern View of Atomic Structure

electrons

protons: found in the nucleus, they have a positive charge equal in magnitude to the electron’s negative charge.

neutrons: found in the nucleus, virtually same mass as a proton but no charge.

The The atomatom contains: contains:


54

The Mass and Change of the Electron, Proton, and NeutronThe Mass and Change of the

Electron, Proton, and Neutron

Particle Mass (kg) Charge

Electron 9.11 10 31 1

Proton 1.67 10 27 1+

Neutron 1.67 10 27 0


55

Nuclear Atom Viewed in Cross Section


56

The Chemists’ Shorthand: Atomic Symbols

The Chemists’ Shorthand: Atomic Symbols

K Element Symbol39

19

Mass number

Atomic number


57

Two Isotopes of Sodium


58

Chemical BondsChemical Bonds

The forces that hold atoms together in compounds. Covalent bonds result from atoms sharing electrons.

Molecule: a collection of covalently-bonded atoms.


59

Two Isotopes of Sodium


60

The Structural Formula for Methane


61

Sodium Chloride


62

The Chemists’ Shorthand:Formulas

The Chemists’ Shorthand:Formulas

Chemical Formula:

Symbols = types of atoms

Subscripts = relative numbers of atoms

CO2

Structural Formula:

Individual bonds are shown by lines.

O=C=O


63

IonsIons

Cation: A positive ion

Mg2+, NH4+

Anion: A negative ion

Cl, SO42

Ionic Bonding: Force of attraction between oppositely charged ions.


64

Periodic TablePeriodic TableElements classified by:

properties

atomic number

Groups (vertical)

1A = alkali metals

2A = alkaline earth metals

7A = halogens

8A = noble gases

Periods (horizontal)


65

The Periodic Table


66

Naming CompoundsNaming Compounds

1. Cation first, then anion

2. Monatomic cation = name of the element

Ca2+ = calcium ion

3. Monatomic anion = root + -ide

Cl = chloride

CaCl2 = calcium chloride

Binary Ionic Compounds:Binary Ionic Compounds:


67

Naming Compounds(continued)


metal forms more than one cation

use Roman numeral in name

PbCl2

Pb2+ is cation

PbCl2 = lead (II) chloride

Binary Ionic Compounds (Type II):Binary Ionic Compounds (Type II):


68

Common Cations and Anions


69



Compounds between two nonmetals

First element in the formula is named first.

Second element is named as if it were an anion.

Use prefixes

Never use mono-

P2O5 = diphosphorus pentoxide

Binary compounds (Type III):Binary compounds (Type III):


70

Flowchart for Naming Binary Compounds

copyright©2000 by houghton mifflin company. all rights reserved. 1 foundations of chemistry a quick...

Documents

houghton mifflin company

metric system

scientific method1

liquid volumecopyright2000

theorya law

fundamental steps

degree of uncertainty

degree of agreement