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 3.1 Properties of Matter
Most common substances exist as solids,
liquids, and gases, which have diverse
physical and chemical properties.
• 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”.
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 Matter
Solid - 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 Properties
Can 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 Properties
Extensive – dependent upon amount of
substance present
Mass
Length
Volume
Intensive – not dependent upon amount
Density
Pressure
Temperature
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
Practice
Problem 3 page 75
Classify each of the following as [being
related to] a physical or a chemical
property:
chem
a. Iron and oxygen form rust
b. Iron is more dense than aluminum phys
c. Magnesium burns when ignited
d. Oil and water don’t mix
e. Mercury melts at 39 C
chem
phys
phys
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
Matter can undergo physical and chemical
changes.
• 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.
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 Changes
Changes 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 Changes
In 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 Mass
Mass 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
Sum of masses of liquid mercury and
gaseous oxygen products equal to original
mass of mercury(II) oxide solid
2HgO(s)  2Hg(l) + O2(g)
Conservation of Mass
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
2HgO(s)  2Hg(l) + O2(g)
Practice
Conservation of mass
Problems 5 – 9 page 78
Problems 13(a-b) page 79
Problems 50 – 55 pages 94 - 95
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 3.3 Mixtures of Matter
Most everyday matter occurs as
mixtures—combinations of two or more
substances.
Objectives
• 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).
Section 3.3 Mixtures of Matter
Objectives (cont)
• 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]
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 - Types
Heterogeneous
• 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 - Types
Homogeneous
• 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 - Types
Table 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 - Types
On 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 Solutions
Ph Solute Solvent
ase (Minor) (Major)
G
Gas
Gas
Example
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)
Solutions
The 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 Atmosphere
Solution 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 Mixtures
Take advantage of differing physical
properties
Filtration – 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 Mixtures
Sublimation (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 Crystallization
When 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 Silicon
Purification by Crystallization
Heated (melted) zone moving left to right
Simple Distillation
Separation 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)
Gasoline
vapors
Fractional
Distillation
of Crude
Oil
Condenser
Gas
Gasoline 38 oC
Kerosene 150 oC
Heating oil 260 oC
Lubricating oil
315 oC - 370 oC
Crude oil from heater
Steam
Residue (asphalt, tar)
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 - Partitioning
Solution 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
Add 2nd
Wait for
2 substances
immiscible partitioning, then
dissolved in
(insoluble)
drain off bottom
water
solvent & shake
S2
S
S
Separatory
Funnel
S1
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
A
A
A
A
A
A
BB B B B B B B
Stationary Phase
A
A
Chromatography
Important 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 up
liquid
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
Detector
Response
Chromatographic Data
time or volume
Data (chromatogram) is usually
represented as a plot of “some” detector
response as a function of either time or
volume (chromatos = color)
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)
Note: Laws of Definite Proportion & Multiple Proportion are
included just for completeness but will be actually discussed
when studying chapter 10 (The Mole)
Section 3.4 Elements and Compounds
A compound is a combination of two or
more elements.
Objectives
• 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
Section 3.4 Elements and Compounds
Objectives (cont)
• 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]
Section 3.4 Elements and Compounds
Key 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
Elements
Pure 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
Elements
Elements 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 Table
Organized 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 - Newest
Elements 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 Elements
Each 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 History
Original 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 Formula
Formed 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 Compounds
Ways 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
http://en.wikipedia.org/wiki/IUPAC_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
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 & Databases
To 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-Dfructofuranoside] 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
http://en.wikipedia.org/wiki/Chemical_abstracts
http://www.cas.org/index.html
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
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
• H2O
CAS [7647-14-5]
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 Search
http://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 Wikipedia
Most 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 Number & Chemical Name - Lipitor
CAS 134523-00-5 Atorvastatin (lowers cholesterol)
[R-(R*, R*)]-2-(4-fluorophenyl)-,-dihydroxy-5-(1methylethyl)-3-phenyl-4-[(phenylamino)carbonyl]-1Hpyrrole-1-heptanoic acid OR
(3S,5S)-7-[2-(4-fluorophenyl)-3-phenyl-4(phenylcarbamoyl)-5-propan-2-ylpyrrol-1-yl]-3,5dihydroxyheptanoic acid
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
http://en.wikipedia.org/wiki/Simplified_molecular_input_line_entry_specification
Simplified molecular input line entry
specification - form of a line notation for
describing structure of chemical molecules
using short ASCII character strings
OC(=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
IUPAC International Chemical Identifier
http://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 Identifier
http://en.wikipedia.org/wiki/International_Chemical_Identifier
Examples of what are called “Standard InChI “
strings:
Chemical Identifiers for Isoprene
Molecular 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 - Summary
Registry 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 Compounds
Cannot 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 Proportions
If 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
Copper Chloride Compounds
Compound I Compound II
Cpd % Cu % Cl Mass Ratio Ratio: cpd I ratio
Cu : Cl
to cpd II ratio
I
64.20 35.80
1.793 : 1
II
47.27 52.73 0.8964 : 1
2.000
Practice
Law of Multiple Proportions
Problems 27 - 28, page 90
Problems 77, 79 page 90
End of Chapter