Unit 10: States of MatterUnit 10: States of Matter(Chapter 13 and 15)(Chapter 13 and 15)

Jennie L. BordersJennie L. Borders

Section 13.1 – The Nature of Section 13.1 – The Nature of GasesGases

Kinetic EnergyKinetic Energy is the energy of is the energy of motionmotion..

The The Kinetic TheoryKinetic Theory is based upon the idea is based upon the idea that all matter is made of that all matter is made of particlesparticles that are that are in constant in constant motionmotion..

The Kinetic TheoryThe Kinetic Theory The particles of a The particles of a gasgas are considered to be are considered to be

small, hard spheres with an insignificant small, hard spheres with an insignificant volumevolume..

No No attractiveattractive or or repulsiverepulsive forces exist forces exist between the particles.between the particles.

The motion of the particles in a gas is The motion of the particles in a gas is rapid, constant, and randomrapid, constant, and random..

All All collisionscollisions between particles in a gas between particles in a gas are are perfectly elasticperfectly elastic..

The Kinetic TheoryThe Kinetic Theory

The particles of a gas travel in The particles of a gas travel in straight-line straight-line pathspaths until they collide with another object. until they collide with another object.

During an During an elastic collisionelastic collision, kinetic energy , kinetic energy is transferred without is transferred without lossloss from one from one particle to another, and the total kinetic particle to another, and the total kinetic energy remains energy remains constantconstant..

Gas PressureGas Pressure

Gas pressureGas pressure is the is the forceforce exerted by a gas exerted by a gas per unit surface area of an object.per unit surface area of an object.

Gas pressureGas pressure is the result of simultaneous is the result of simultaneous collisionscollisions of billions of rapidly moving of billions of rapidly moving particles in a gas with an particles in a gas with an objectobject..

An An empty spaceempty space with no particles and no with no particles and no pressure is called a pressure is called a vacuumvacuum..

Atmospheric PressureAtmospheric Pressure AirAir exerts pressure on the earth because exerts pressure on the earth because

gravitygravity holds the air particles in the Earth’s holds the air particles in the Earth’s atmosphereatmosphere..

Atmospheric pressure Atmospheric pressure decreasesdecreases as you as you climb a mountain because the climb a mountain because the densitydensity of of Earth’s atmosphere Earth’s atmosphere decreasesdecreases as the as the elevation elevation increasesincreases..

BarometerBarometer

A A barometerbarometer is a device used to measure is a device used to measure atmospheric pressure.atmospheric pressure.

Units of PressureUnits of Pressure

The The SI unit of pressureSI unit of pressure is the is the Pascal (Pa)Pascal (Pa).. The most common units of pressure are The most common units of pressure are

the the atmosphere, millimeters of mercury, atmosphere, millimeters of mercury, kilopascals, and torrkilopascals, and torr..

1 atm = 760 mm Hg = 101.3 kPa = 760 Torr1 atm = 760 mm Hg = 101.3 kPa = 760 Torr

Conversions of PressureConversions of Pressure

Sample Problem 13.1Sample Problem 13.1

A pressure gauge records a pressure of A pressure gauge records a pressure of 450 kPa. What is this measurement 450 kPa. What is this measurement expressed in millimeters of mercury?expressed in millimeters of mercury?

Answer: Answer: 450 kPa x 450 kPa x 760 mm Hg760 mm Hg = = 3400 mm Hg3400 mm Hg 101.3 kPa101.3 kPa

Conversion of PressureConversion of Pressure

Practice Problem 1Practice Problem 1

What pressure in atmospheres does a gas What pressure in atmospheres does a gas exert at 385 mm Hg?exert at 385 mm Hg?

Answer:Answer:385 mm Hg x 385 mm Hg x 1 atm 1 atm = = 0.51 atm0.51 atm 760 mm Hg760 mm Hg

Kinetic EnergyKinetic Energy

As a substance is As a substance is heatedheated, its particles , its particles absorb absorb energyenergy, some of which is , some of which is storedstored within the particles.within the particles.

This increase in This increase in kinetic energykinetic energy results in results in an increase in an increase in temperaturetemperature..

The particles in any substanceThe particles in any substance

at a given at a given temperature temperature have have

a wide range of a wide range of kinetic energieskinetic energies..

Kinetic EnergyKinetic Energy Kinetic energyKinetic energy and and Kelvin temperatureKelvin temperature are are

directlydirectly proportional. proportional. An An increaseincrease in average kinetic energy in average kinetic energy causes the temperature to causes the temperature to increaseincrease.. A A decreasedecrease in average kinetic in average kinetic energy causes the temperature to energy causes the temperature to decreasedecrease.. Absolute zeroAbsolute zero is the temperature at is the temperature at which the motion of particles which the motion of particles theoretically theoretically stopsstops..

Section AssessmentSection Assessment1.1. Briefly describe the assumptions of the Briefly describe the assumptions of the

kinetic theory.kinetic theory.

2.2. How is the Kelvin temperature of a How is the Kelvin temperature of a substance related to the average kinetic substance related to the average kinetic energy of its particles?energy of its particles?

3.3. Convert the following pressures to Convert the following pressures to kilopascals.kilopascals.

a. 0.95 atma. 0.95 atm b. 45 mm Hgb. 45 mm Hg

Answers:Answers:a. a. 96 kPa96 kPa b. b. 6.0 kPa6.0 kPa

Section 13.2 – The Nature of Section 13.2 – The Nature of LiquidsLiquids

The high The high kinetic energykinetic energy in gases and in gases and liquids allows the particles to liquids allows the particles to flowflow past one past one another.another.

Substances that can Substances that can flowflow are called are called fluidsfluids.. Intermolecular forcesIntermolecular forces keep the particles in keep the particles in

a liquid close together, which is why a liquid close together, which is why liquids have a definite liquids have a definite volumevolume,,

unlike gases.unlike gases.

EvaporationEvaporation

The conversion of a liquid to a The conversion of a liquid to a gasgas that is that is not not boilingboiling is referred to as is referred to as evaporationevaporation..

During evaporation, only molecules with During evaporation, only molecules with the the highest kinetic energyhighest kinetic energy can escape the can escape the surfacesurface of a liquid. of a liquid.

The particles left in the liquid have a lower The particles left in the liquid have a lower average kinetic energyaverage kinetic energy resulting in a lower resulting in a lower temperaturetemperature..

Vapor PressureVapor Pressure

Vapor pressureVapor pressure is a measure of the is a measure of the forceforce exerted by a gas above a exerted by a gas above a liquidliquid..

An increase in An increase in temperaturetemperature

increases the increases the vapor pressurevapor pressure

produced by a liquid.produced by a liquid.

Boiling PointBoiling Point

The rate of The rate of evaporationevaporation increases increases

as the temperature as the temperature increasesincreases.. When a When a liquidliquid is heated to a temperature at is heated to a temperature at

which particles throughout the liquid have which particles throughout the liquid have enough enough kinetic energykinetic energy to vaporize, the liquid to vaporize, the liquid begins to begins to boilboil..

The temperature at which the The temperature at which the vapor pressurevapor pressure of of the liquid is equal to the the liquid is equal to the external pressureexternal pressure on the on the liquid is the liquid is the boiling pointboiling point..

Boiling and PressureBoiling and Pressure Because atmospheric pressure is Because atmospheric pressure is lowerlower at at

higherhigher altitudes, boiling points altitudes, boiling points decreasedecrease at at higher altitudes.higher altitudes.

At higher At higher external pressureexternal pressure, the boiling , the boiling point point increasesincreases..

Section AssessmentSection Assessment

1.1. In terms of kinetic energy, explain how a In terms of kinetic energy, explain how a molecule in a liquid evaporates.molecule in a liquid evaporates.

2.2. Explain why the boiling point of a liquid Explain why the boiling point of a liquid varies with atmospheric pressure.varies with atmospheric pressure.

3.3. Explain how evaporation lowers the Explain how evaporation lowers the temperature of a liquid.temperature of a liquid.

Section 13.3 – The Nature of SolidsSection 13.3 – The Nature of Solids

The general properties of The general properties of solidssolids reflect the reflect the orderlyorderly arrangement of their particles and arrangement of their particles and the the fixedfixed locations of their particles. locations of their particles.

When you When you heatheat a solid, its particles a solid, its particles vibratevibrate more rapidly as their more rapidly as their kinetickinetic

energyenergy increases. increases. The The melting pointmelting point is the is the temperature at which a temperature at which a solidsolid changes into a changes into a liquidliquid..

CrystalsCrystals In a In a crystal crystal the particles are arranged in an the particles are arranged in an

orderly, repeating, three-dimensional orderly, repeating, three-dimensional patternpattern called a crystal called a crystal latticelattice..

The The smallestsmallest group of particles within a group of particles within a crystal that retains the crystal that retains the geometric shapegeometric shape of of the crystal is known as the the crystal is known as the unit cellunit cell..

MeltingMelting Ionic solidsIonic solids have have highhigh melting points melting points

(above 300(above 300ooC).C). Molecular solidsMolecular solids have have lowlow melting points melting points

(below 300(below 300ooC).C). Not all solids Not all solids meltmelt; some just ; some just decomposedecompose. .

(Ex. Wood)(Ex. Wood)

AllotropesAllotropes

AllotropesAllotropes are two or more different are two or more different molecular forms of the same molecular forms of the same elementelement in in the same the same physical statephysical state..

A common example is carbon: A common example is carbon: diamond, diamond, graphite, and bucky ballgraphite, and bucky ball..

Other examples include Other examples include phosphorus, phosphorus, sulfur, and oxygensulfur, and oxygen..

Non-Crystalline SolidsNon-Crystalline Solids An An amorphous solidamorphous solid lacks an lacks an orderedordered

internal structure.internal structure. Examples include Examples include rubber, plastic, and rubber, plastic, and

asphaltasphalt.. GlassGlass is an amorphous is an amorphous

solid that is a solid that is a supercooledsupercooled

liquidliquid. Glass is formed by . Glass is formed by

cooling a liquid into a rigid cooling a liquid into a rigid

state without state without crystallizingcrystallizing..

Section AssessmentSection Assessment

1.1. In general, how are the particles In general, how are the particles arranged in solids?arranged in solids?

2.2. How do allotropes of an element differ?How do allotropes of an element differ?

3.3. How do the melting points of ionic solids How do the melting points of ionic solids generally compare with those of generally compare with those of molecular solids?molecular solids?

Section 13.4 – Changes of StateSection 13.4 – Changes of State

The change of a substance from a The change of a substance from a solidsolid to to a a vaporvapor without passing through the liquid without passing through the liquid state is called state is called sublimationsublimation..

Dry ice and iodineDry ice and iodine are two examples of are two examples of solids that sublimate.solids that sublimate.

Phase DiagramsPhase Diagrams

The relationship among the The relationship among the solid, liquid, solid, liquid, and gaseousand gaseous states of a substance can be states of a substance can be represented in a single graph called a represented in a single graph called a phase diagramphase diagram..

The The lineslines on a phase diagram indicate the on a phase diagram indicate the conditions at which conditions at which twotwo phases occur in phases occur in equilibriumequilibrium..

The The triple pointtriple point describes the only set of describes the only set of conditions at which all conditions at which all threethree phases occur phases occur in in equilibriumequilibrium..

Phase Diagram of WaterPhase Diagram of Water

Section AssessmentSection Assessment

1.1. What does the triple point on a phase What does the triple point on a phase diagram describe?diagram describe?

Section 15.1 – Water and Its Section 15.1 – Water and Its PropertiesProperties

A water molecule has a A water molecule has a dipole momentdipole moment because the oxygen is much more because the oxygen is much more electronegativeelectronegative than the hydrogens. than the hydrogens.

This strong This strong dipole momentdipole moment causes water causes water molecules to have strong molecules to have strong attractionsattractions for for each other. These attractions are called each other. These attractions are called hydrogen bondinghydrogen bonding..

Hydrogen bondingHydrogen bonding describes describes many of the properties ofmany of the properties of water such as water such as surface tensionsurface tension and vapor pressureand vapor pressure..

Ice and Liquid WaterIce and Liquid Water

WaterWater is one of the few substances in is one of the few substances in which the solid state is which the solid state is less denseless dense than the than the liquid state.liquid state.

This is the reason that ice This is the reason that ice floatsfloats in water. in water. The structure of The structure of iceice is a regular is a regular openopen

framework of water molecules arranged framework of water molecules arranged like a like a honeycombhoneycomb..

When ice When ice meltsmelts, the framework , the framework collapsescollapses and the water molecules pack close and the water molecules pack close together, making the liquid together, making the liquid more densemore dense than the ice.than the ice.

Ice and Liquid WaterIce and Liquid Water

Section AssessmentSection Assessment

1.1. What causes the high surface tension What causes the high surface tension and low vapor pressure of water?and low vapor pressure of water?

2.2. How would you describe the structure of How would you describe the structure of ice?ice?

Section 15.2 – Homogeneous Section 15.2 – Homogeneous Aqueous SystemsAqueous Systems

An An aqueous solutionaqueous solution is water that contains is water that contains dissolveddissolved substances. substances.

In a In a solutionsolution, the dissolving medium is the , the dissolving medium is the solventsolvent, and the dissolved particles are the , and the dissolved particles are the solutesolute..

A A solventsolvent dissolves a dissolves a

solutesolute..

Dissolving Ionic SolidsDissolving Ionic Solids As individual solute As individual solute ionsions break away from break away from

a a crystalcrystal, the negatively and positively , the negatively and positively charged charged ionsions become surrounded by become surrounded by solventsolvent molecules and the ionic crystal molecules and the ionic crystal dissolvesdissolves..

Dissolution RuleDissolution Rule As a rule, As a rule, polarpolar solvents such a solvents such a waterwater

dissolve dissolve polar polar solutes such as solutes such as ethanolethanol.. As a rule, As a rule, nonpolarnonpolar solvents such a solvents such a

gasolinegasoline dissolve dissolve nonpolarnonpolar solutes such as solutes such as oiloil..

This relationship can be This relationship can be

summed up in the expressionsummed up in the expression

“ “like dissolves likelike dissolves like.”.”

ElectrolytesElectrolytes

An An electrolyteelectrolyte is a compound that is a compound that conducts an conducts an electric currentelectric current when it is in when it is in an aqueous solution or in the molten state.an aqueous solution or in the molten state.

All All ionicionic compounds are electrolytes compounds are electrolytes because they dissolve into because they dissolve into ionsions..

A A strongstrong electrolyte electrolyte fullyfully breaks into breaks into ionsions.. A A weakweak electrolyte only electrolyte only partiallypartially breaks breaks

into into ionsions..

NonelectrolyteNonelectrolyte

A substance that does not conduct A substance that does not conduct electricity is a electricity is a nonelectrolytenonelectrolyte..

Some Some polar polar compounds are compounds are nonelectrolytes in a nonelectrolytes in a pure statepure state but become but become electrolytes when electrolytes when dissolveddissolved in water. in water.

HydratesHydrates

A compound that contains A compound that contains waterwater is called is called a a hydratehydrate..

In writing the formula of a hydrate, use a In writing the formula of a hydrate, use a dotdot to connect the to connect the formulaformula of the of the compound and the compound and the numbernumber of water of water molecules per formula unit.molecules per formula unit.

Example:Example:

CuSOCuSO44 .. 5H 5H22OO

Section AssessmentSection Assessment1.1. In the formation of a solution, how does the In the formation of a solution, how does the

solvent differ from the solute?solvent differ from the solute?2.2. Describe what happens to the solute and the Describe what happens to the solute and the

solvent when an ionic compounds dissolves in solvent when an ionic compounds dissolves in water.water.

3.3. Why are all ionic compounds electrolytes?Why are all ionic compounds electrolytes?4.4. How do you write the formula for a hydrate?How do you write the formula for a hydrate?5.5. Which of the following substances dissolve to Which of the following substances dissolve to

a significant extent in water?a significant extent in water?

a. CHa. CH44 b. KClb. KCl c. Hec. He

d. MgSOd. MgSO44 e. sucrosee. sucrose f. NaHCOf. NaHCO33

Section 15.3 – Heterogeneous Section 15.3 – Heterogeneous Aqueous SystemsAqueous Systems

A A suspensionsuspension is a mixture from which is a mixture from which particles particles settle outsettle out upon standing because upon standing because the solute particles are very the solute particles are very largelarge..

An example is An example is Italian salad dressingItalian salad dressing..

ColloidsColloids A A colloidcolloid is a heterogeneous mixture is a heterogeneous mixture

containing particles that are containing particles that are smallersmaller than a than a suspensionsuspension but larger than a but larger than a solutionsolution..

A colloid’s particles do not A colloid’s particles do not settle outsettle out with with time.time.

A colloid’s particles are A colloid’s particles are tootoosmallsmall to be separated by to be separated byfilteringfiltering..

Examples include Examples include whippedwhipped cream, milk, and Jell-Ocream, milk, and Jell-O..

Section AssessmentSection Assessment

1.1. How does a suspension differ from a How does a suspension differ from a solution?solution?

2.2. What distinguishes a colloid from a What distinguishes a colloid from a suspension and a solution?suspension and a solution?

3.3. Could you separate a colloid by filtering?Could you separate a colloid by filtering?