3.1 Properties of Matter

3.2 Changes in Matter

3.3 Mixtures of Matter

3.4 Elements and Compounds (for treatment of simple hydrocarbons and isomers, see ppt Section 21.4 & Related – Isomers)

Chapt 3 Matter – Properties & Change

Section 3.1 Properties of Matter

• Identify the characteristics of a substance.

• Distinguish between physical and chemical properties and changes and be able to give examples of each.

• Distinguish between intensive and extensive physical properties and be able to give examples of each type.

• Differentiate among the physical states of matter; know the meaning of the term “vapor”.

Most common substances exist as solids, liquids, and gases, which have diverse physical and chemical properties.

Section 3.1 Properties of Matter

Key Concepts

• The three common states of matter are solid, liquid, and gas. Physical properties can be observed without altering a substance’s composition.

• Chemical properties describe a substance’s ability to combine with or change into one or more new substances.

• External conditions can affect both physical and chemical properties.

Substance

Matter that has a uniform and unchanging composition (aka pure substance)

• Copper (Cu – an element)• Salt (sodium chloride, NaCl)• Dionized water (H2O)

Any matter that is not a pure substance is a mixture – see section 3.3

• Tap water (has dissolved minerals)

States of MatterSolid - Definite shape and volume

Liquid - Flows, constant V, takes shape of its container

Gas - Conforms to and fills entire volume of container

Vapor – gaseous state of room temperature solid/liquid

Physical PropertiesCan be observed or measured without changing samples composition

• Density Color Luster Hardness• Conductivity Melting/boiling points

Physical Properties of Common Substances – Table 3.1

Extensive/Intensive PropertiesExtensive – dependent upon amount of substance present

MassLengthVolume

Intensive – not dependent upon amountDensityPressureTemperature

Ignore book example re: scent & spices

Chemical Property

Ability of a substance to combine with or change into one or more other substances

Properties of Cu – Table 3.2

Note distinctions between physical and chemical properties

PracticeProblem 3 page 75

Classify each of the following as [being related to] a physical or a chemical property:

chem

chem

phys

phys

phys

a. Iron and oxygen form rust

b. Iron is more dense than aluminum

c. Magnesium burns when ignited

d. Oil and water don’t mix

e. Mercury melts at 39 C

Chapt 3 Matter – Properties & Change

3.1 Properties of Matter

3.2 Changes in Matter

3.3 Mixtures of Matter

3.4 Elements and Compounds (for treatment of simple hydrocarbons and isomers, see ppt Section 21.4 & Related – Isomers)

Section 3.2 Changes in Matter

• Define physical change and list several common physical changes.

• Define chemical change and list several indications that a chemical change has taken place.

• Apply the law of conservation of mass to chemical reactions.

Matter can undergo physical and chemical changes.

Section 3.2 Changes in Matter

Key Concepts

• A physical change alters the physical properties of a substance without changing its composition. A chemical change, also known as a chemical reaction, involves a change in a substance’s composition.

• In a chemical reaction, reactants form products.

• The law of conservation of mass states that mass is neither created nor destroyed during a chemical reaction; it is conserved.

massreactants = massproducts

Physical Properties and ChangesChanges don’t alter chemical nature

Changes in shape from applied mechanical forces• Cut, bend, crumple

Phase changes• Melting, boiling, condensation, freezing• Melting and boiling points (see table 3.1)

are intensive physical properties useful in identifying a substance

Chemical ChangesIn a chemical change (reaction), reactants (R) form products (P)

R P

New Substances Created• Rusting – Iron (R) to iron oxide (P)• Fermentation – sugar (R) to

alcohol (P)• Combustion – methane (R) to CO2

(P) and H2O (P)

Evidence of Chemical Change

Rusting; properties that change include:

Color: metallic grey brownish orange

Attracted to magnet: yes no

Chemical reaction always produces a change in properties

Conservation of MassMass is neither created or destroyed in a chemical reaction; it is conserved

Mass reactants = Mass products

Lavoisier (1743-1794) credited with concept; studied thermal composition of mercury (II) oxide to mercury & oxygen

Proof of it depended on development of analytical balance capable of detecting small mass changes

Thermal Decomposition of HgO

2HgO(s) 2Hg(l) + O2(g)

Sum of masses of liquid mercury and gaseous oxygen products equal to original mass of mercury(II) oxide solid

Conservation of Mass

2HgO(s) 2Hg(l) + O2(g)

Example problem 3.1 page 78

10.00 g HgO heated to produce 9.26 g Hg

Mass of oxygen formed in reaction?Knowns: mHgO = 10.00 g mHg = 9.26 g

Unknown: mO2 ?

mreactants = mproducts Law of Conservation of Mass

mHgO = mHg + mO2 mO2 = mHgO mHg

mO2 = 10.0 g 9.26 g = 0.74 g of oxygen

PracticeConservation of mass

Problems 5 – 9 page 78

Problems 13(a-b) page 79

Problems 50 – 55 pages 94 - 95

3.1 Properties of Matter

3.2 Changes in Matter

3.3 Mixtures of Matter

3.4 Elements and Compounds (for treatment of simple hydrocarbons and isomers, see ppt Section 21.4 & Related – Isomers)

Chapt 3 Matter – Properties & Change

Section 3.3 Mixtures of Matter

• Define and distinguish between substances and mixtures.

• Define and distinguish between homogeneous and heterogeneous mixtures and be able to give examples of each.

• Classify and give examples of the seven different types of solutions (3 possible states for the solution and 3 combinations of phases of solute and solvent for the liquid and solid phase solutions).

Most everyday matter occurs as mixtures—combinations of two or more substances.

Objectives

Section 3.3 Mixtures of Matter

• Name and describe various mixture separation techniques and identify which technique would be most appropriate for a given separation problem.

• Describe the role that mobile and stationary phases play in chromatographic separation techniques.

• Describe how affinity differences play a role in liquid-liquid and chromatographic separation techniques. [material only partially in textbook]

Objectives (cont)

Section 3.3 Mixtures of Matter

Key Concepts

• A mixture is a physical blend of two or more pure substances in any proportion.

• Solutions are homogeneous mixtures.

• Mixtures can be separated by physical means. Common separation techniques include filtration, distillation, crystallization, sublimation, and chromatography.

Matter – Classification Scheme

Mixtures

Combination of two or more pure substances in which each pure substance retains its individual chemical properties

• Composition variable• Number of possible mixtures is infinite• Most everyday matter occurs as mixture

Mixtures - TypesHeterogeneous• Not smoothly blended [may appear to be

just by looking at it but will not be at the microscopic level]

• Individual substances remain distinct Sand & water Paint, mayonnaise [heterogeneous at a

microscopic level – not all heterogeneous mixtures are readily identified as such by the naked eye]

Mixtures - TypesHomogeneous• Constant composition throughout – even

down to the microscopic level• Single phase (gas, liquid or solid)

[although heterogeneous mixtures can also be a single phase such as a water/oil emulsion]

• More commonly used term is solution Salt & water

Mixtures and Compounds Iron and Sulfur

S

Fe

Physically mixed - can be separated by physical means

React chemically - cannot be separated by physical means

Solutions - TypesTable 3.3 “Types of Solution Systems” from the textbook; table 3.3 is not completely correct

Liquid-gas example wrong – water droplets are 2nd phase (incompatible with definition of solution)

Liquid-liquid example misleading – seawater itself is a solution of a solid dissolved in liquid water, so liquid is same for both; much better example is solution formed from 2 pure liquids, such as a solution of isopropyl alcohol in water (what you get from a drugstore)

Solutions - TypesOn the next slide is an expanded (and correct) version of Table 3.3

1st column is phase of solution itself

2nd column is phase of solute – the “stuff” that is being dissolved in the solvent to form the solution

By definition there is less of the solute than there is of the solvent

3rd column is phase of solvent

Can dissolve both gas & liquid in a solid!

Types of SolutionsPhase

Solute(Minor)

Solvent(Major)

Example

G Gas Gas Air – N2, O2, Ar

L Gas Liquid Soda – CO2 /H2O

L Liquid Liquid Antifreeze – Glycol / H2O

L Solid Liquid Salt water

S Gas Solid H2 in Pd or Pt

S Liquid Solid Dental Amalgam (Hg/Ag)

S Solid Solid Brass (Cu/Zn alloy)

SolutionsThe following 3 slides are intended as examples of how common substances such as air and water can be more complicated than one might expect

You are not expected to know the actual compositions

Composition of Dry Air (Solution)

Layers of AtmosphereSolution with continuously variable composition

Horizontally homogeneous (sort of – lots of point sources of pollutants)Vertically inhomogeneous but still a solution in local region

Substances Found in Natural Waters

Any natural water (tap or bottled) is a complicated homogeneous mixture (a solution) and if dust and sand/soil particles are counted, is a heterogeneous mixture

Separating MixturesTake advantage of differing physical propertiesFiltration – heterogeneous mixture• Solid from liquid

Distillation – typically liquid-liquid solutions; also solid-liquid (salt water)

• Depends upon difference in boiling points• Most volatile (lower bp) material removed 1st

Crystallization – liquid-solid solutions• Remove enough solvent so solubility of solute

exceeded – very high purity crystals possible

Separating MixturesSublimation (Phase change process in which solid changes directly into vapor) – can use in separation of solids if only one sublimates [extremely limited in actual practice]

Chromatography – separates components of mixture (mobile phase) based on ability of each component to travel across surface of another material (stationary phase) [this is most widely used separation technique in chemistry]

Filtration Good for Solid/Liquid Separations

Selective CrystallizationWhen KNO3(s) crystallized from aqueous solution of KNO3 containing CuSO4

(blue) as an impurity, CuSO4 remains in solution

KNO3 (white) crystallized from hot, saturated solution is virtually pure

Zone Refining of SiliconPurification by Crystallization

Heated (melted) zone moving left to right

Simple DistillationSeparation technique based on differences in boiling points (BPs) of substances involved – physical process, not chemical

Distillation often synonymous with “simple” distillation; single evaporation followed by condensation of vapors

Simple distillation - works well when BPs differ by ≥ 25 C (rule of thumb)

Batch technique (single filling of apparatus)

Gas

Gasoline 38 oC

Kerosene 150 oCHeating oil 260 oC

Lubricating oil 315 oC - 370 oC

Crude oil from heater

SteamResidue (asphalt, tar)

CondenserGasoline vapors

Fractional Distillation of Crude

Oil

Separating Mixtures

Forces exist between molecules

Details of molecular shape, size, and charge influence magnitude of force between any 2 molecules

For example, there are strong forces between oppositely charged molecules (ions)

Separating Mixtures

Forces between certain types of molecules are stronger than than for other types of molecules

• Ones with stronger forces said to have an affinity for each other

Can use affinity differences as basis for a separation technique

Separating Mixtures - PartitioningSolution with A & B dissolved in water

If A has higher affinity for another solvent than B does, can exploit to separate A & B

If water & 2nd solvent in contact, A will tend to concentrate in 2nd solvent

A & B said to partition between the 2 solvents – basis for liquid-liquid extraction process

Liquid-Liquid Extraction

2 substances dissolved in

water

Separatory Funnel

S

S2

S1

Wait for partitioning, then drain off bottom

S

Add 2nd immiscible (insoluble)

solvent & shake

Chromatography

Can exploit affinity differences in different way by using chromatography

Key to technique is mobile (moving) phase and a stationary phase

Molecules separate out on basis of their affinity for stationary phase

Stationary Phase

A

B

A

B

A

B

A

B

A

B

A

B

A

B

A

B

ChromatographyImportant and widely used technique

Many types: (m)=mobile (s)=stationary• VPC vapor phase – gas (m)/liquid (s)• LPC liquid phase – liquid(m)/solid(s)• Paper – liquid(m)/paper(s)• HPLC – high pressure LPC• IEC – ion exchange – ions (m)/resin(s)

Lots of others, often coupled with other types of instruments

Paper chromatography of ink(a) Line of mixture to be separated placed at one end of sheet of porous paper

Paper chromatography of ink(b) The paper acts as wick to draw upliquid

Paper chromatography of ink(c) Component with weakest attraction (least affinity) for paper travels faster than components that cling to paper (have high affinity for paper)

Column Chromatography

Gas Chromatography

Chromatographic Data

Data (chromatogram) is usually represented as a plot of “some” detector response as a function of either time or volume (chromatos = color)

Dete

cto

rR

esp

on

se

time or volume

3.1 Properties of Matter

3.2 Changes in Matter

3.3 Mixtures of Matter

3.4 Elements and Compounds (for treatment of simple hydrocarbons and isomers, see ppt Section 21.4 & Related – Isomers)Note: Laws of Definite Proportion & Multiple Proportion are included just for completeness but will be actually discussed when studying chapter 10 (The Mole)

Chapt 3 Matter – Properties & Change

Section 3.4 Elements and Compounds

• Define and distinguish between elements and compounds and recognize that a compound’s properties can be very different from the properties of its constituent elements.

• Identify a method for separating a compound into elements.• Classify a given material as a mixture or a pure substance

and to further classify it as homogeneous or heterogeneous mixture or as an element or as a compound. Should also be able to give an example of each category

• Describe the organization of elements in the periodic table.• Identify the number of currently recognized elements and

the number of naturally occuring elements

A compound is a combination of two or more elements.

Objectives

Section 3.4 Elements and Compounds

• Name the two most abundant elements in the universe and the five most abundant elements in the Earth’s crust, atmosphere and oceans (both sets in order of relative abundance). [Material not entirely in book]

• Distinguish between common & systematic chemical names.

• Name and describe the commonly used chemical identifiers

• Explain the value of a CAS registry number (or other comparable chemical identifiers) in finding information on existing compounds. [Material not in book]

• Identify the SMILES and InChI strings as chemical identifiers that are based on chemical structure and describe the advantages of these identifiers. [Material not in book]

Objectives (cont)

Section 3.4 Elements and CompoundsKey Concepts

• Elements cannot be broken down into simpler substances.

• Elements are organized in the periodic table of the elements.

• Compounds are chemical combinations of two or more elements and their properties differ from the properties of their component elements.

• Chemical registry numbers and other chemical identifiers help avoid some problems with complicated chemical names and make it easier to find information about compounds. In some cases, they provide a way to look for information based on the compound’s structure.

Matter – Classification Scheme

ElementsPure substance that can’t be separated into simpler substances by physical or chemical means

92 naturally occurring elements (Tc, # 43, only in trace amounts - unstable) – remaining elements must be synthesized

ElementsElements have name and chemical symbol

Named elements have 1 or 2 letter symbol with only 1st letter capitalized (C, Au, Pt)

Unnamed or undiscovered elements given 3 letter placeholder (temporary) symbol (Uut, Uuo) and latin or latin/greek name for its atomic number

Uuo = Ununoctium = latin for 118 + “ium”

Elements – Periodic TableOrganized into periodic table of elements (see end of book or pages 178-9) ordered by atomic number (number of protons in nucleus); currently 114 named elements

Columns (vertical) = groups or families

Elements in same group tend to have similar chemical and physical properties

Rows (horizontal) = periods

Table “periodic” because pattern of variation of properties repeats in each period

Elements - NewestElements with atomic numbers 114 and 116 officially named 5/2012 as Flerovium (Fl) and Livermorium (Lv), respectively. Copernicium (Cn), atomic number 112 officially named 2/2010.

Elements 113, 115, 117 (newest – April 2010), 118 have claimed to have been made, but evidence not yet convincing enough for official recognition by IUPAC

Official current total = 114 elements

Periodic Table of ElementsEach box shows atomic number and the element’s symbol

Newest elements Fl & Lv; remainder claimed to have been made but have not been officially recognized as existing

Periodic Table – Basic HistoryOriginal form of table published by Russian chemist Dmitri Mendeleev in 1869

Based on similar properties and ordered by element masses

Has since been refined – see chapter 6 (The Periodic Table and Periodic Law)

Elements - Abundance

Hydrogen most abundant and helium second most abundant elements in universe (H estimated to make up ~ 75% of mass of universe)

Statistics for elemental abundance on Earth focused on composition of Earth’s crust, its oceans and its atmosphere

Top five elements in order: O Si Al Fe Ca

Compound and Chemical FormulaFormed from 2 or more elements that are combined chemically (bonded to one another)

• Exception: S8 (1 element compound)

Simple compounds clearly and uniquely Identified by chemical formula - created from chemical symbols of elements and subscripts indicating number of atoms of that element

• H2O NaCl CH4 CaSO4

Overview – Identifying CompoundsWays of identifying a compound include:

1. Chemical formula

2. Chemical name

a. Common name

b. Systematic Name

3. Chemical structure (drawing)

4. Other (to be described)

Will use the term “chemical identifier” to refer to any of the above choices

Chemical Formula and Isomers

As compounds become more complex (especially organic ones), the chemical formula does not uniquely represent a single compound

Isomers – different compounds which have same chemical formula

Details are in PowerPoint presentation “Chapt 21 – Hydrocarbons [selected]” which covers simple alkanes and isomers of alkanes and other organic compounds

Systematic vs Common Names

Common names (water, aspirin) convey little to no chemical information

Elaborate rules exist for assigning names to chemical substances on basis of their structures – called systematic names

Systematic (rule-based) names uniquely identify given substance; rule definitions = system of chemical nomenclature

Chemical Nomenclature

Developed and kept up to date under auspices of International Union of Pure and Applied Chemistry (IUPAC), which publishes official (systematic) rules for naming organic and inorganic compounds

Primary aim - provide methodology for assigning descriptors (names and formulas) to chemical species so that they can be identified without ambiguity

http://en.wikipedia.org/wiki/IUPAC_nomenclature

Compound Names

Given substance may have several common or trivial names; ordinary cane sugar, for example, is more formally known as "sucrose“

Formal, systematic name for sucrose is α-D-glucopyranosyl-(1,2)-β-D-fructofuranoside

Compound Names - Drawbacks

Problems associated with names:

1. They aren’t necessarily unique; can be multiple ways of naming a given compound using the official rules of chemical nomenclature

2. For even moderately complicated compounds, can be difficult to figure out the correct name

3. Long, complex names are difficult to use in a search engine

Chemical Information & DatabasesTo find information about a substance from formal chemical database or from a less structured source of information (Google), need to be able to identify the substance using some sort of chemical identifier

Identifier could be common chemical name (table sugar, sucrose), a systematic chemical name [α-D-glucopyranosyl-(1,2)-β-D-fructofuranoside] or some alternate chemical identifier (like using SS number in place of person’s name to obtain data about a person)

Chemical Databases & Identifiers

Indexing of structure, composition and properties of new & existing compounds done by several organizations

To get around problem of complicated and multiple names for a substance, major databases of chemicals use chemical registry numbers, accession numbers or other chemical identifiers not based on name; some of these chemical identifiers are based directly on molecular structure

Chemical Databases & Identifiers

Chemical Abstracts Service (CAS) Registry Numbers are most commonly encountered chemical identifier for compounds (especially in US); also known as CAS RNs or CAS Numbers

Other registries and their associated chemical identifiers exist and offer alternatives / advantages to CAS numbers

Use of structure-based identifiers has accelerated over past 5 – 10 years

Compounds & CAS Registry Numbers

Number itself has no inherent chemical significance but provides an unambiguous, unique way to identify a chemical substance or molecular structure when there are many possible systematic, generic, proprietary, or trivial names

http://www.cas.org/index.htmlhttp://en.wikipedia.org/wiki/Chemical_abstracts

Compounds & CAS Registry Numbers

CAS number can contain up to 10 digits, divided by hyphens into 3 parts

Right most digit is a check digit used to verify the validity and uniqueness of number

Examples:• NaCl CAS [7647-14-5]• H2O CAS [7732-18-5]

Using CAS Number or Name

Many online databases will accept a CAS numbers as a search term

Wolframalpha (computational knowledge engine) accepts CAS numbers to provide extensive compound information – see example on left side of following slide

Right hand side of slide shows result from entering a compound name (benzoic acid); CAS number shown as part of output

http://www.wolframalpha.com/

Compounds from Wolfram Searchhttp://www.wolframalpha.com/input/?i=benzoic+acid

Other Registry Numbers and IDs

Wolframalpha and many other sources return a list of “chemical identifiers” – alternate ways that compound is indexed or described; benzoic acid identifiers:

Other IDs for Benzoic Acid - Wolframalpha

Other IDs for Benzoic Acid - Wikipedia

First hit from Google search on benzoic acid is Wikipedia article

Chemical IDs Listed by WikipediaMost important / widely used (not specific to a particular database)

CAS number – Chemical Abstracts Service Registry Number

InChI - textual identifier (text string) for chemical substances that represents chemical structures

SMILES – similar to InChI

CAS 134523-00-5 Atorvastatin (lowers cholesterol)

[R-(R*, R*)]-2-(4-fluorophenyl)-,-dihydroxy-5-(1-methylethyl)-3-phenyl-4-[(phenylamino)carbonyl]-1H-pyrrole-1-heptanoic acid OR

(3S,5S)-7-[2-(4-fluorophenyl)-3-phenyl-4-(phenylcarbamoyl)-5-propan-2-ylpyrrol-1-yl]-3,5-dihydroxyheptanoic acid

CAS Number & Chemical Name - Lipitor

Structure-Based Chemical Identifiers

Most direct is to draw compound’s structure (various ways of doing this)

Alternative is to encode connectivity (what’s connected to what) of atoms within a molecule into a text string

Two main string based IDs:

SMILES and InChI (IN chee)

SMILES

Simplified molecular input line entry specification - form of a line notation for describing structure of chemical molecules using short ASCII character stringsOC(=O)C(N)CC1=CC=C(O)C=C1 is an example of a SMILES string

SMILES strings can be imported by most molecule editors for conversion back into 2D drawings or 3D models of molecules

http://en.wikipedia.org/wiki/Simplified_molecular_input_line_entry_specification

IUPAC International Chemical Identifierhttp://en.wikipedia.org/wiki/International_Chemical_Identifier

InChI - textual identifier for chemical substances, designed to provide standard and human-readable way to encode molecular information & to facilitate database searches for such information

XML-based text coding system for chemical structure; codes are unique and capable of representing detailed and nuanced features of chemical structures for robust chemical structure representation

IUPAC International Chemical Identifierhttp://en.wikipedia.org/wiki/International_Chemical_Identifier

Examples of what are called “Standard InChI “ strings:

Chemical Identifiers for IsopreneMolecular formula: C5H8

Systematic names:

2-Methylbutadiene;

2-Methyl-1,3-butadiene

Common names:

Isoprene; Isopentadiene

CAS RN: 78-79-5

SMILES: C=CC(C)=C; C(C)=CC=C;

C(C=C)C=C; C=C(C=C)C

InChI: 1/C5H8/c1-4-5(2)3/h4H,1-2H2,3H3

Advantages of Structure-Based IDs

CAS RNs and similar registry numbers for other databases can only be used for existing compounds that have been registered by that database

Stucture-based IDs (InChI, SMILES) can encode compounds that might not exist

In addition, they allow for powerful structure-based searches such as “find existing compounds that have structures similar to my target compound”

Compound Identification - Summary

Chemical formula (NaCl, C3H8) OK for small compounds but not for larger organics – many, many compounds have same formula (isomers)

Common and formal chemical names (sodium chloride, propane) OK for small compounds but difficult for non-specialists to determine correct name for larger ones unless use computer and input structure

Compound Identification - SummaryRegistry numbers (CAS, etc.) good way to access information about existing compounds from chemical databases

InChI Chemical ID provides means to generate searchable ID from structure

SMILES Similar to InChI – encodes structure in text string

Structural formulas (easiest to digest)

Decomposing CompoundsCannot break down into components by physical means, but sometimes can by chemical means – requires input of energy because compound is more stable than its separate component elements

Electrolysis considered to be an example of a chemical process (doesn’t involve chemicals but does cause chemical change) that breaks down a compound – most common example is water electrolysis

Separating Water into Hydrogen and Oxygen Using Electrolysis

Separating Water into Hydrogen and Oxygen Using Electrolysis

Compounds

Properties can be quite different than component elements

See following slide on reaction of Na metal with chlorine gas to form NaCl

Some Properties of Sodium, Chlorine, and Sodium Chloride

Remainder of this section will be treated when doing chapter 10 (The

Mole)

Law of Definite Proportions

Regardless of amount, compound composed of same elements in same proportion by mass statement that compound’s formula doesn’t change with amount of compound present

• H2O = formula for water no matter how much water you have – proportions always same, mole ratio same, mass ratios same

Law of Definite (or Constant) Proportion

(or Composition)Both sources of

calcium carbonate (CaCO3) have same

% composition

Law of Definite Proportions

Focus here is % composition from some chemical analysis

% by mass = 100 mass element mass compound

Law of Definite Proportions% by mass = 100 mass element mass compound

Analysis of 20.00 g & 500.0 g samples same have same composition

Practice

Mass % & Law of Definite Proportions

Problems 19 - 23, page 88

Problem 29, page 90

Problems 72(a-b), 74 – 76 page 95

Problems 78, 80 page 96

Law of Multiple ProportionsIf elements form >1 compound, those compounds will have compositions that are small, whole-number multiples of each other

Focus: ratio of mass ratios = integer

Water vs Hydrogen Peroxide

H2O (O:H 16:2) vs H2O2 (O:H 32:2)• Ratio of Mass ratios

O:H (H2O2) / O:H (H2O) = 2:1

Atomic Basis of Law of Multiple Proportions

Ratio of number of atoms within each compound is integer ratio of mass ratios of compounds must be same integer

Law of Multiple Proportions

Compound I Compound II

Copper Chloride Compounds

Cpd % Cu % Cl Mass Ratio

Cu : Cl

Ratio: cpd I ratio to cpd II ratio

I 64.20 35.80 1.793 : 12.000

II 47.27 52.73 0.8964 : 1

Practice

Law of Multiple Proportions

Problems 27 - 28, page 90

Problems 77, 79 page 90

End of Chapter