Chapter 2Chapter 2

“Matter and “Matter and Change”Change”

General ChemistryGeneral Chemistry

Section 2.1Section 2.1Properties of MatterProperties of Matter

OBJECTIVES:OBJECTIVES:IdentifyIdentify properties of properties of matter as extensive or matter as extensive or intensive.intensive.

Section 2.1Section 2.1Properties of MatterProperties of Matter

OBJECTIVES:OBJECTIVES:DefineDefine physical property, physical property, and and listlist several common several common physical properties of physical properties of substances.substances.

Section 2.1Section 2.1Properties of MatterProperties of Matter

OBJECTIVES:OBJECTIVES:DifferentiateDifferentiate among three among three states of matter.states of matter.

Section 2.1Section 2.1Properties of MatterProperties of Matter

OBJECTIVES:OBJECTIVES:DescribeDescribe a physical change. a physical change.

MatterMatterMatter is anything that: a) has Matter is anything that: a) has

mass, and b) takes up spacemass, and b) takes up spaceMass = a measure of the Mass = a measure of the

amount of material the object amount of material the object contains (don’t confuse this with contains (don’t confuse this with weight, a measure of gravity)weight, a measure of gravity)

Volume = a measure of the Volume = a measure of the space occupied by the objectspace occupied by the object

Describing MatterDescribing Matter

Properties used to describe Properties used to describe matter can be classified as:matter can be classified as:

1)1) ExtensiveExtensive – depends on the – depends on the amountamount of matter in the sample of matter in the sample

- Mass, volume, calories are - Mass, volume, calories are examplesexamples

2)2) IntensiveIntensive – depends on the – depends on the typetype of of matter, not the amount presentmatter, not the amount present

- Hardness, Density, Boiling Point- Hardness, Density, Boiling Point

Properties are…Properties are…Words that describe matter Words that describe matter

(adjectives)(adjectives)Physical PropertiesPhysical Properties- a property that - a property that

can be observed and measured can be observed and measured without changing the material’s without changing the material’s composition.composition.

Examples- color, hardness, m.p., b.p.Examples- color, hardness, m.p., b.p.Chemical PropertiesChemical Properties- a property that - a property that

can only be observed by changing the can only be observed by changing the composition of the material. composition of the material.

Examples- ability to burn, decompose, Examples- ability to burn, decompose, ferment, react with, etc.ferment, react with, etc.

States of matterStates of matter1)1) SolidSolid- matter that can not flow - matter that can not flow

(definite shape) and has definite (definite shape) and has definite volume.volume.

2)2) LiquidLiquid- definite volume but takes the - definite volume but takes the shape of its container (flows).shape of its container (flows).

3)3) GasGas- a substance without definite - a substance without definite volume or shape and can flow.volume or shape and can flow.

VaporVapor- a substance that is currently a - a substance that is currently a gas, but normally is a liquid or solid at gas, but normally is a liquid or solid at room temperature. (Which is correct: room temperature. (Which is correct: “water gas”, or “water vapor”?)“water gas”, or “water vapor”?)

States of MatterStates of Matter

Solid

Liquid

Gas

Definite Volume?

YES

YES

NO

Definite Shape?

YES

NO

NO

Result of a TemperatureIncrease?

Small Expans.

Small Expans.

Large Expans.

Will it Compress?

NO

NO

YES

44thth state: state: PlasmaPlasma - - formed at high formed at high temperatures; ionized phase of temperatures; ionized phase of

matter as found in the sunmatter as found in the sun

Three Main Phases – Three Main Phases –

Solid Liquid Gas

Melt Evaporate

CondenseFreeze

Copper Phases - SolidCopper Phases - Solid

Copper Phases - LiquidCopper Phases - Liquid

Copper Phases – Vapor (gas)Copper Phases – Vapor (gas)

Physical vs. Chemical Physical vs. Chemical ChangeChangePhysical changePhysical change will change the will change the

visible appearance, without visible appearance, without changing the composition of the changing the composition of the material.material.Boil, melt, cut, bend, split, crackBoil, melt, cut, bend, split, crackIs boiled water still water?Is boiled water still water?

Can be Can be reversiblereversible, or , or irreversibleirreversibleChemical changeChemical change - a change where - a change where

a new form of matter is formed.a new form of matter is formed.Rust, burn, decompose, fermentRust, burn, decompose, ferment

Section 2.2Section 2.2MixturesMixtures

OBJECTIVES:OBJECTIVES:CategorizeCategorize a sample of a sample of matter as a substance or a matter as a substance or a mixture.mixture.

Section 2.2Section 2.2MixturesMixtures

OBJECTIVES:OBJECTIVES:DistinguishDistinguish between between homogeneous and homogeneous and heterogeneous samples of heterogeneous samples of matter.matter.

Section 2.2Section 2.2MixturesMixtures

OBJECTIVES:OBJECTIVES:DescribeDescribe two ways that two ways that components of mixtures components of mixtures can be separated.can be separated.

MixturesMixtures Mixtures are a physical blendMixtures are a physical blend of at of at

least two substances; have variable least two substances; have variable composition. They can be either:composition. They can be either:

1)1) Heterogeneous Heterogeneous – the mixture is not – the mixture is not uniform in compositionuniform in composition

• Chocolate chip cookie, gravel, soil.Chocolate chip cookie, gravel, soil.

2)2) Homogeneous Homogeneous - same composition - same composition throughout; called “throughout; called “solutionssolutions””

• Kool-aid, air, salt waterKool-aid, air, salt water Every part keeps it’s own Every part keeps it’s own

properties.properties.

Solutions are homogeneous mixturesSolutions are homogeneous mixturesMixed molecule by molecule, thus Mixed molecule by molecule, thus

too small to see the different partstoo small to see the different partsCan occur between any state of Can occur between any state of

matter: gas in gas; liquid in gas; matter: gas in gas; liquid in gas; gas in liquid; solid in liquid; solid in gas in liquid; solid in liquid; solid in solid (alloys), etc.solid (alloys), etc.

Thus, based on the distribution of Thus, based on the distribution of their components, mixtures are their components, mixtures are called called homogeneoushomogeneous or or heterogeneousheterogeneous..

Phase?Phase?

The term “phase” is used to The term “phase” is used to describe any part of a sample describe any part of a sample with uniform composition of with uniform composition of properties.properties.

A homogeneous mixture A homogeneous mixture consists of a consists of a singlesingle phase phase

A heterogeneous mixture A heterogeneous mixture consists of consists of two or moretwo or more phases. phases.

Separating MixturesSeparating Mixtures

Some can be separated easily by Some can be separated easily by physical means: rocks and physical means: rocks and marbles, iron filings and sulfur (use marbles, iron filings and sulfur (use magnet) magnet)

Differences in physical properties Differences in physical properties can be used to separate mixtures.can be used to separate mixtures.

FiltrationFiltration - separates a solid from - separates a solid from the liquid in a heterogeneous the liquid in a heterogeneous mixture (by size) – mixture (by size) –

Separation of a MixtureSeparation of a MixtureComponents of dyes such as ink may be separated by paper chromatography.

Separation of a MixtureSeparation of a MixtureDistillation: takes advantage of different boiling points.

NaCl boils at 1415 oC

Section 2.3Section 2.3Elements and CompoundsElements and Compounds

OBJECTIVES:OBJECTIVES:ExplainExplain the differences the differences between an element and a between an element and a compound.compound.

DensityDensity Density: An Important Property of MatterDensity: An Important Property of Matter The The densitydensity of a sample of matter is… of a sample of matter is…the the

quantity of mass of that substance that occupies quantity of mass of that substance that occupies one unit of vol.; density is a constant ratio of one unit of vol.; density is a constant ratio of mass to volumemass to volume

Formula for density: Formula for density: D = m/VD = m/V Density Can Be Used To Identify SubstancesDensity Can Be Used To Identify Substances

The The units for densityunits for density are always are always massmass / / volumevolume units. We will most often use the units:units. We will most often use the units:

g/mLg/mL for fluids (liquids and gases) for fluids (liquids and gases) g/cm3g/cm3 for solids for solids

Example 1: Example 1: A piece of lead (Pb) has A piece of lead (Pb) has a mass of 22.7 g and occupies a a mass of 22.7 g and occupies a volume of 2.00 cm3. What is the volume of 2.00 cm3. What is the density of Pb?density of Pb?

Example 2: Example 2: A piece of lead (Pb) A piece of lead (Pb) takes up 16.20 cm3 of space. Use takes up 16.20 cm3 of space. Use your answer from Example 1 to find your answer from Example 1 to find the mass of the Pb piece.the mass of the Pb piece.

Example 3: Example 3: A piece of lead (Pb) has A piece of lead (Pb) has a mass of 1544 g. Use your answer a mass of 1544 g. Use your answer from Example 1 to find the volume of from Example 1 to find the volume of the piece of Pb.the piece of Pb.

Section 2.3Section 2.3Elements and CompoundsElements and Compounds

OBJECTIVES:OBJECTIVES:DistinguishDistinguish between a between a substance and a mixture.substance and a mixture.

Section 2.3Section 2.3Elements and CompoundsElements and Compounds

OBJECTIVES:OBJECTIVES:IdentifyIdentify the chemical the chemical symbols of elements, and symbols of elements, and namename elements given elements given their symbols.their symbols.

Substances are either:a) elements, orb) compounds

Substances: element or Substances: element or compoundcompoundElementsElements- simplest kind of matter- simplest kind of matter

cannot be broken down any simpler and cannot be broken down any simpler and still have properties of that element!still have properties of that element!

all all oneone kind of atom. kind of atom.CompoundsCompounds are substances that can be are substances that can be

broken down broken down onlyonly by chemical methods by chemical methodswhen broken down, the pieces have when broken down, the pieces have

completely different properties than the completely different properties than the original compound.original compound.

made of made of two or moretwo or more atoms, chemically atoms, chemically combined (not just a physical blend!)combined (not just a physical blend!)

Compound vs. MixtureCompound vs. Mixture

Compound Mixture

Made of one kindof material

Made of more thanone kind of material

Made by a chemical change

Made by a physical change

Definitecomposition

Variablecomposition

Which is it?Which is it?

Elements vs. CompoundsElements vs. Compounds

Compounds Compounds cancan be broken be broken down into simpler substances down into simpler substances by chemical means, but by chemical means, but elements elements cannotcannot..

A “A “chemical changechemical change” is a ” is a change that produces matter change that produces matter with a with a different compositiondifferent composition than the original matter.than the original matter.

Chemical ChangeChemical ChangeA change in which one or more substances are converted into different substances.

Heat and

light are often evidence of a chemical change.

Properties of CompoundsProperties of CompoundsQuite different properties than Quite different properties than

their component elements.their component elements.Due to a CHEMICAL CHANGE, the Due to a CHEMICAL CHANGE, the

resulting compound has new and resulting compound has new and different properties:different properties:• Table sugar – carbon, hydrogen, Table sugar – carbon, hydrogen,

oxygenoxygen• Sodium chloride – sodium, chlorineSodium chloride – sodium, chlorine• Water – hydrogen, oxygenWater – hydrogen, oxygen

Classification of MatterClassification of Matter

Symbols & FormulasSymbols & FormulasCurrently, there are Currently, there are 117117 elements elementsElements have a 1 or two letter Elements have a 1 or two letter

symbolsymbol, and compounds have a , and compounds have a formulaformula..

An element’s first letter always An element’s first letter always capitalized; if there is a second capitalized; if there is a second letter, it is written lowercase: B, Ba, letter, it is written lowercase: B, Ba, C, Ca, H, HeC, Ca, H, He

Some names come from Latin or Some names come from Latin or other languagesother languages

Section 2.4Section 2.4Chemical ReactionsChemical Reactions

OBJECTIVES:OBJECTIVES:DescribeDescribe what happens what happens during a chemical change.during a chemical change.

Section 2.4Section 2.4Chemical ReactionsChemical Reactions

OBJECTIVES:OBJECTIVES:IdentifyIdentify four possible clues four possible clues that a chemical change has that a chemical change has taken place.taken place.

Chemical ChangesChemical ChangesThe ability of a substance to The ability of a substance to

undergo a specific chemical change undergo a specific chemical change is called a is called a chemical propertychemical property..• iron plus oxygen forms rust, so the iron plus oxygen forms rust, so the

ability to rust is a chemical property of ability to rust is a chemical property of ironiron

During a chemical change (also During a chemical change (also called chemical reaction), the called chemical reaction), the composition of matter always composition of matter always changes. changes.

Chemical Reactions are…Chemical Reactions are…When one or more substances are When one or more substances are

changed into new substances.changed into new substances.ReactantsReactants- the material you start - the material you start

withwithProductsProducts- what you make- what you makeThe products will have NEW The products will have NEW

PROPERTIES different from the PROPERTIES different from the reactants you started withreactants you started with

Arrow points from the reactants Arrow points from the reactants toto the new productsthe new products

Recognizing Chemical Recognizing Chemical ChangesChanges1)1) EnergyEnergy is absorbed or released (temperature is absorbed or released (temperature

changes hotter or colder)changes hotter or colder) EndothermicEndothermic a process that absorbs heat from the a process that absorbs heat from the

surroundings surroundings ExothermicExothermic a process that releases heat to it a process that releases heat to it

surroundingssurroundings

2) 2) ColorColor changes changes 3) production (bubbling, fizzing, or odor change; 3) production (bubbling, fizzing, or odor change;

smoke)smoke) 4) formation of a4) formation of a precipitateprecipitate - a solid that separates - a solid that separates

from solution (won’t dissolve)from solution (won’t dissolve) 5) 5) Irreversibility Irreversibility - not easily reversed- not easily reversedBut, there are examples of these that are not chemical – But, there are examples of these that are not chemical –

boiling water bubbles, etc.boiling water bubbles, etc.

Activation EnergyActivation Energy

As a rule , chemical reactions need a As a rule , chemical reactions need a slight “push” to get started. This slight “push” to get started. This “push” is called activation energy.“push” is called activation energy.

It’s the minimum energy needed to It’s the minimum energy needed to start a reaction.start a reaction.