Physical and Chemical Changes Pure Substances Mixtures States of Matter

Physical and Chemical Physical and Chemical ChangesChanges

Pure SubstancesPure Substances

MixturesMixtures

States of MatterStates of Matter

What is matter? What is matter?

MatterMatter is anything that takes up space and is anything that takes up space and has mass. has mass.


The building blocks of matter are atoms and The building blocks of matter are atoms and compounds.compounds.

An An atomatom is the smallest unit of an element is the smallest unit of an element that still has all the properties of the that still has all the properties of the elementelement

An An elementelement is a pure substance that has is a pure substance that has only one type of atomsonly one type of atoms


A A compoundcompound is made of two or more types is made of two or more types of atoms that are chemically bondedof atoms that are chemically bonded

A A moleculemolecule is the smallest unit of an is the smallest unit of an element or compound that retains all the element or compound that retains all the properties of that element or compound properties of that element or compound

Matter is identified based on Matter is identified based on its propertiesits properties

PropertiesProperties

ColorColor

ShapeShape

TextureTexture

DensityDensity

Melting and boiling pointMelting and boiling point

Electrical conductivityElectrical conductivity

Heat conductivity Heat conductivity

Malleability Malleability

DuctilityDuctility

Reactivity Reactivity

Index of RefractionIndex of Refraction

FlammabilityFlammability

HardnessHardness

Vapor pressureVapor pressure


can be divided into two types;can be divided into two types;

Physical & ChemicalPhysical & Chemical

Chemical propertiesChemical properties

can not be observed and measured can not be observed and measured without changing the identity of the without changing the identity of the matter. Chemical properties are harder matter. Chemical properties are harder to observe than physical properties.to observe than physical properties.

Chemical propertiesChemical properties

Reaction with acidsReaction with acids

Reaction with bases Reaction with bases (alkalis)(alkalis)

Reaction with oxygen Reaction with oxygen (combustion)(combustion)

Ability to act as Ability to act as oxidizing agentoxidizing agent

Ability to act as Ability to act as reducing agentreducing agent

Reaction with other Reaction with other elementselements

Decomposition into Decomposition into simpler substancessimpler substances

CorrosionCorrosion

Physical propertiesPhysical properties

Can be observed and measured without Can be observed and measured without changing the identity of the matterchanging the identity of the matter

Color, density, malleability Color, density, malleability


Can beCan be intensive intensive or or extensiveextensive

Intensive propertiesIntensive properties

Are Independent (does Are Independent (does notnot depend on) of depend on) of the amount of matterthe amount of matter

ColorColor OdorOdor LusterLuster - How shiny a substance is. - How shiny a substance is. MalleabilityMalleability - The ability of a substance to be beaten into thin sheets. - The ability of a substance to be beaten into thin sheets. DuctilityDuctility - The ability of a substance to be drawn into thin wires. - The ability of a substance to be drawn into thin wires. ConductivityConductivity - The ability of a substance to allow the flow of energy or - The ability of a substance to allow the flow of energy or

electricity. electricity. HardnessHardness - How easily a substance can be scratched. - How easily a substance can be scratched. Melting/Freezing PointMelting/Freezing Point - The temperature at which the solid and liquid phases - The temperature at which the solid and liquid phases

of a substance are in equilibrium at atmospheric pressure. of a substance are in equilibrium at atmospheric pressure. Boiling PointBoiling Point - The temperature at which the vapor pressure of a liquid is - The temperature at which the vapor pressure of a liquid is

equal to the pressure on the liquid (generally atmospheric pressure). equal to the pressure on the liquid (generally atmospheric pressure). DensityDensity

ExtensiveExtensive propertiesproperties

doesdoes change with the amount of matter change with the amount of matter

Mass Mass - A measurement of the amount of matter in - A measurement of the amount of matter in a object (grams). a object (grams).

WeightWeight - A measurement of the gravitational force - A measurement of the gravitational force of attraction of the earth acting on an object. of attraction of the earth acting on an object.

VolumeVolume - A measurement of the amount of space - A measurement of the amount of space a substance occupies. a substance occupies.

LengthLength

physical changephysical change

A A physical changephysical change occurs when a substance occurs when a substance does not change into something new does not change into something new

The properties of a substance do not changeThe properties of a substance do not change

Ice melting is still waterIce melting is still water

Physical changesPhysical changes are easy to undo are easy to undo

Matter can undergo changes Matter can undergo changes

A A chemical changechemical change occurs when a occurs when a substance changes into something new. substance changes into something new. This occurs due to heating, chemical This occurs due to heating, chemical reaction, etc. reaction, etc.

Matter can undergo changesMatter can undergo changes

You can tell a chemical change has You can tell a chemical change has occurred if the properties, like density, occurred if the properties, like density, of the original substance changesof the original substance changes

Chemical changesChemical changes are usually not are usually not reversible reversible

Signs of a Signs of a chemicalchemical change change

Formation of a gasFormation of a gas

Formation of a solid (precipitate)Formation of a solid (precipitate)

Color change (Unexpected)Color change (Unexpected)

Release of light or heatRelease of light or heat

MatterMatter

Matter can be either Matter can be either

A pure substanceA pure substance

or a or a mixture of substancesmixture of substances

What is a pure substance?What is a pure substance?

A pure substance has only one type of matter in the sample

Cannot be separated into simpler Cannot be separated into simpler

substances by physical methods (physical substances by physical methods (physical

changes like sieving or centrifuging)changes like sieving or centrifuging)

Can only be changed in identity and Can only be changed in identity and

properties by chemical methodsproperties by chemical methods

Properties do not varyProperties do not vary

Characteristic of Pure SubstancesCharacteristic of Pure Substances

What is a Pure Substance?What is a Pure Substance?

CompoundsCompounds

Can be Can be decomposed decomposed into simpler into simpler

substances by substances by chemical chemical changes, changes,

always in a always in a definite ratiodefinite ratio

ElementsElements

Cannot be Cannot be decomposed decomposed into simpler into simpler

substances by substances by chemical chemical changeschanges

What is a Pure Substance?What is a Pure Substance?

CompoundsCompounds

Consists of two or Consists of two or more different more different types of atomstypes of atoms (molecules)(molecules)

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ElementsElements

Consist of only one Consist of only one kind of atom, kind of atom, Can exist as either Can exist as either atoms (e.g. argon) atoms (e.g. argon) or molecules* (e.g., or molecules* (e.g., nitrogen). nitrogen).

MoleculesMolecules

*Molecules*Molecules consist of two or more consist of two or more atoms of the same element, or atoms of the same element, or different elements, which are different elements, which are chemically bound together. Note that chemically bound together. Note that the two nitrogen atoms that make up the two nitrogen atoms that make up a nitrogen molecule move as a unit. a nitrogen molecule move as a unit. NN22

AtomsAtoms

Elements are made up of atoms, Elements are made up of atoms,

Atoms are the smallest particle that has the Atoms are the smallest particle that has the properties of the element. properties of the element.


CompoundCompound

– composed of 2 or more elements composed of 2 or more elements in a fixed ratioin a fixed ratio

– properties differ from those of properties differ from those of individual elementsindividual elements

– EXEX: table salt (NaCl): table salt (NaCl)

Sodium is a solid shiny metal which Sodium is a solid shiny metal which reacts wreacts w

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem


Law of Definite CompositionLaw of Definite Composition

– A given compound always contains the same, A given compound always contains the same, fixed ratio of elements.fixed ratio of elements.

Law of Multiple ProportionsLaw of Multiple Proportions

– Elements can combine in different ratios to Elements can combine in different ratios to form different compounds.form different compounds.



For example…For example…

Two different compounds, Two different compounds, each has a definite composition.each has a definite composition.

Carbon, C Oxygen, O Carbon monoxide, CO

Carbon, C Oxygen, O Oxygen, O Carbon dioxide, CO2


MixturesMixtures

Variable combination of 2 or more Variable combination of 2 or more pure substances.pure substances.

Heterogeneous Homogeneous


MixturesMixtures

Is a collection of pure substances simply Is a collection of pure substances simply mixed together.mixed together.

The composition is variable – can changeThe composition is variable – can changeThe properties of each pure substance The properties of each pure substance

remains intact.remains intact.

Mixtures are two or more substances that are NOT chemically combined.

Mixtures do not have constant properties

MixturesMixtures

Mixtures are two or more substances that are NOT chemically combined.

Homogeneous MixturesHomogeneous MixturesHomogeneous mixtures look the same

throughout but can be separated by physical means

(centrifuge, filtering, picking out pieces, density, boiling, magnetism etc.).

Examples: milk, salt water, sand and sugar

Have the same composition Have the same composition throughoutthroughout

Components are indistinguishableComponents are indistinguishable

May or may not scatter lightMay or may not scatter light

Examples: soda, air Examples: soda, air

Signs of a Homogeneous MixtureSigns of a Homogeneous Mixture

MixturesMixtures

SolutionSolution– homogeneoushomogeneous– very small particlesvery small particles– no Tyndall effectno Tyndall effect Tyndall Effect

– particles don’t settleparticles don’t settle– EXEX: rubbing alcohol: rubbing alcohol


SolutionsSolutions

Solutions are homogenous mixtures that do not scatter light. These mixtures are created when something is completely dissolved in pure water.

They are easily separated by distillation or evaporation.

Examples: sugar water, salt water

Suspension - a type of mixtureSuspension - a type of mixture

SuspensionSuspension– heterogeneousheterogeneous– large particleslarge particles– Tyndall effectTyndall effect– particles settleparticles settle– EXEX:: fresh-squeezed fresh-squeezed

lemonadelemonade


Heterogeneous Mixture Heterogeneous Mixture

Heterogeneous mixtures are composed of large pieces that are easily separated by physical means

(ie. density, polarity, metallic properties).

Do not have same composition Do not have same composition throughoutthroughout

Components are distinguishable – Components are distinguishable –

easy to tell that it is differenteasy to tell that it is different

Examples: fruit salad, granite Examples: fruit salad, granite

Signs of a Heterogeneous MixtureSigns of a Heterogeneous Mixture

MixturesMixtures

Examples of mixtures are Examples of mixtures are milk, milk,

wood, wood, concrete, concrete,

air, air, granite, granite, motor oil,motor oil,

chocolate, chocolate, and elephants. and elephants.

MATTER

Can it be physically separated?

Homogeneous Mixture

(solution)

Heterogeneous Mixture Compound Element

MIXTURE PURE SUBSTANCE

yes no

Can it be chemically decomposed?

noyesIs the composition uniform?

noyes


Classification of MatterClassification of Matter

Materials

HomogeneousHeterogeneous

Heterogeneousmixture

Homogeneousmixture

Substance

Element Compound Solution Mixture

Speci

fic /

Gen

eral

Order / Disorder

Smoot, Smith, Price, Chemistry A Modern Course, 1990, page 43

Elements, Compounds, and MixturesElements, Compounds, and Mixtures

(a)an element(hydrogen)

(b)a compound(water)

(c)a mixture(hydrogen and oxygen)

(d)a mixture(hydrogenand oxygen)

Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 68

hydrogenatoms hydrogen

atoms

oxygen atoms

Separating Separating MixturesMixtures

Methods of Separation:Methods of Separation:

FiltrationFiltrationSievingSievingGravity separationGravity separationDistillation and CondensationDistillation and CondensationCrystallization and EvaporationCrystallization and EvaporationFlotationFlotationMagnetic separationMagnetic separationChromatographyChromatographyCentrifugingCentrifuging

FiltrationFiltration

FiltrationFiltration

SievingSieving

Gravity separationGravity separation

DistillationDistillation

DistillationDistillation

Commercial Tequila stillCommercial Tequila still Copper alcohol stillCopper alcohol still

CrystallisationCrystallisation

CrystallizationCrystallization

CrystallisationCrystallisation

Froth FlotationFroth Flotation

Magnetic separationMagnetic separation

ChromatographyChromatography

CentrifugingCentrifuging

CentrifugingCentrifuging

•Solids•Liquids•Gases

Gas, Liquid, and SolidGas, Liquid, and Solid

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 441

Gas Liquid Solid

•Have a definite shape•Have a definite volume

Molecules are held close together and there is very little movement between them.

Kinetic Molecular Theory

SolidSolid

H2O(s) Ice


•Have an indefinite shape•Have a definite volume

Kinetic Molecular Theory:Atoms and molecules have more space between them than a solid does, but less than a gas (ie. It is more “fluid”.)

LiquidLiquid

H2O(l) Water


In a liquid• molecules are in constant motion

• there are appreciable intermolecular forces

• molecules are close together

• Liquids are almost incompressible

• Liquids do not fill the container

•Have an indefinite shape•Have an indefinite volume

Kinetic Molecular Theory:

Molecules are moving in random patterns with varying amounts of distance between the particles.

GasGas

H2O(g) Steam


Some Properties of Solids, Liquids, and GasesSome Properties of Solids, Liquids, and Gases

Property Solid Liquid Gas

Shape Has definite shape Takes the shape of Takes the shape the container of its container

Volume Has a definite volume Has a definite volume Fills the volume of the container

Arrangement of Fixed, very close Random, close Random, far apartParticles

Interactions between Very strong Strong Essentially noneparticles

Changing states requires energy in either the form of heat. Changing states may also be due to the change in pressure in a system.

Changing of StatesChanging of States

FreezingFreezing – Liquid – Liquid Solid – exothermicSolid – exothermic

MeltingMelting – Solid – Solid liquid – endothermic liquid – endothermic

EvaporationEvaporation– Liquid – Liquid gas –endothermic gas –endothermic

CondensationCondensation- Gas - Gas liquid -exothermic liquid -exothermic

Sublimation Sublimation Solid Solid gas endothermicgas endothermic

DepositionDeposition Gas Gas solid -exothermic solid -exothermic

PHASE CHANGEPHASE CHANGE

PHASE DIAGRAMSPHASE DIAGRAMS

MELTMELTMELTMELT

FREEZEFREEZEFREEZEFREEZE

SUBLIMESUBLIMESUBLIMESUBLIME

DEPOSITDEPOSITDEPOSITDEPOSIT

TRIPLETRIPLEPOINTPOINT

CRITICALCRITICALPOINTPOINT

11VAPORIZEVAPORIZEVAPORIZEVAPORIZE

CONSENSECONSENSECONSENSECONSENSE

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Physical and Chemical Changes Pure Substances Mixtures States of Matter