chapter 9 “states of matter”. section 9.1 the nature of gases objectives: objectives: describe...
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Chapter 9Chapter 9“States of Matter”“States of Matter”
Section 9.1Section 9.1The Nature of GasesThe Nature of Gases
OBJECTIVES:OBJECTIVES:
DescribeDescribe the assumptions the assumptions of the “kinetic theory” as it of the “kinetic theory” as it applies to gases.applies to gases.
Section 9.2Section 9.2The Nature of GasesThe Nature of Gases
OBJECTIVES:OBJECTIVES:
InterpretInterpret gas pressure in gas pressure in terms of kinetic theory.terms of kinetic theory.
Section 9.3Section 9.3The Nature of GasesThe Nature of Gases
OBJECTIVES:OBJECTIVES:
DefineDefine the relationship the relationship between Kelvin temperature between Kelvin temperature and average kinetic energy.and average kinetic energy.
Section 9.1Section 9.1The Nature of GasesThe Nature of Gases
KineticKinetic refers to motion refers to motion The energy an object has The energy an object has
because of it’s motion is called because of it’s motion is called kinetic energykinetic energy
The The kinetic theorykinetic theory states that the states that the tiny particles in tiny particles in all forms of matterall forms of matter are in are in constant motionconstant motion!!
Section 9.1Section 9.1The Nature of GasesThe Nature of Gases
Three basic assumptionsThree basic assumptions of the kinetic of the kinetic theory as it applies to gases:theory as it applies to gases:
#1#1. Gas is . Gas is composed of particlescomposed of particles-- usually molecules or atomsusually molecules or atoms Small, hard spheresSmall, hard spheres Insignificant volume; relatively far Insignificant volume; relatively far
apart from each otherapart from each other No attraction or repulsion between No attraction or repulsion between
particlesparticles
Section 9.1Section 9.1The Nature of GasesThe Nature of Gases
#2#2. Particles in a gas move rapidly . Particles in a gas move rapidly in in constant constant randomrandom motion motion Move in straight paths, changing Move in straight paths, changing
direction only when colliding with one direction only when colliding with one another or other objectsanother or other objects
Average speed of OAverage speed of O22 in air at 20 in air at 20 ooC is C is an amazing 1700 km/h!an amazing 1700 km/h!
Random walk is a very short distance Random walk is a very short distance
- Page 385 Top
Section 9.1Section 9.1The Nature of GasesThe Nature of Gases
#3#3. Collisions are . Collisions are perfectly perfectly elasticelastic-- meaning kinetic energy meaning kinetic energy is transferred without loss from is transferred without loss from one particle to another- the total one particle to another- the total kinetic energy remains constantkinetic energy remains constant
Section 9.2Section 9.2The Nature of GasesThe Nature of Gases
Gas PressureGas Pressure – defined as the force – defined as the force exerted by a gas per unit surface exerted by a gas per unit surface area of an objectarea of an object Due to: a) Due to: a) force of collisionsforce of collisions, and b) , and b)
number of collisionsnumber of collisions No particles present? Then there No particles present? Then there
cannot be any collisions, and thus no cannot be any collisions, and thus no pressure – called a pressure – called a vacuumvacuum
Section 9.2Section 9.2The Nature of GasesThe Nature of Gases
Atmospheric pressureAtmospheric pressure results from results from the collisions of air molecules with the collisions of air molecules with objectsobjects Decreases as you climb a mountain Decreases as you climb a mountain
because the air layer thins out as because the air layer thins out as elevation increaseselevation increases
BarometerBarometer is the measuring device is the measuring device for atmospheric pressure, which is for atmospheric pressure, which is dependent upon weather & altitudedependent upon weather & altitude
Measuring PressureMeasuring Pressure
The first device for measuring atmosphericpressure was developed by Evangelista Torricelli during the 17th century.
The device was called a “barometer”
Baro = weight Meter = measure Torricelli
Section 9.2Section 9.2The Nature of GasesThe Nature of Gases
The SI unit of pressure is the The SI unit of pressure is the pascal (Pa)pascal (Pa) At sea level, atmospheric pressure is At sea level, atmospheric pressure is
about 101.3 about 101.3 kilopascalskilopascals (kPa) (kPa) Older units of pressure include Older units of pressure include
millimeters of mercury (mm Hg), and millimeters of mercury (mm Hg), and atmospheres (atm) – both of which atmospheres (atm) – both of which came from using a mercury barometercame from using a mercury barometer
Section 9.2Section 9.2The Nature of GasesThe Nature of Gases
Mercury BarometerMercury Barometer – Fig. 9.2, page – Fig. 9.2, page 239 – a straight glass tube filled 239 – a straight glass tube filled with Hg, and closed at one end; with Hg, and closed at one end; placed in a dish of Hg, with the placed in a dish of Hg, with the open end below the surfaceopen end below the surface At sea level, the mercury would rise to At sea level, the mercury would rise to
760 mm high at 25 760 mm high at 25 ooC- called one C- called one standard atmospherestandard atmosphere (atm) (atm)
An Early An Early BarometerBarometer
The normal pressure due to the atmosphere at sea level can support a column of mercury that is 760 mm high.
Section 9.2Section 9.2The Nature of GasesThe Nature of Gases
Equal pressures:1 atm = 760 mm Hg = 101.3 kPaEqual pressures:1 atm = 760 mm Hg = 101.3 kPa
Practice Problems 5 & 6 pg 240Practice Problems 5 & 6 pg 240 Most modern barometers do not Most modern barometers do not
contain mercury- too dangerouscontain mercury- too dangerous These are called These are called aneroid barometersaneroid barometers, ,
and contain a sensitive metal and contain a sensitive metal diaphragm that responds to the diaphragm that responds to the number of collisions of air molecules – number of collisions of air molecules – this is the type in our classroomthis is the type in our classroom
The Aneroid BarometerThe Aneroid Barometer
Section 9.3Section 9.3The Nature of GasesThe Nature of Gases
For gases, it is important to relate For gases, it is important to relate measured values to standardsmeasured values to standards Standard values are defined as a Standard values are defined as a
temperature of 0temperature of 0 o oC and a pressure of C and a pressure of 101.3 kPa, or 1 atm101.3 kPa, or 1 atm
This is called This is called Standard Standard Temperature and PressureTemperature and Pressure, or , or STPSTP
Section 9.3Section 9.3The Nature of GasesThe Nature of Gases
What happens when a substance is What happens when a substance is heated? Particles absorb energy!heated? Particles absorb energy! Some of the energy is storedSome of the energy is stored within within
the particles- this is potential energy, the particles- this is potential energy, and does not raise the temperatureand does not raise the temperature
Remaining energy speeds up the Remaining energy speeds up the particles (increases average kinetic particles (increases average kinetic energy)- thus energy)- thus increases temperatureincreases temperature
Section 9.3Section 9.3The Nature of GasesThe Nature of Gases
The particles in any collection have The particles in any collection have a wide range of kinetic energies, a wide range of kinetic energies, from very low to very high- but most from very low to very high- but most are somewhere in the middle, thus are somewhere in the middle, thus the term the term averageaverage kinetic energy kinetic energy is is usedused The higher the temperature, the wider The higher the temperature, the wider
the range of kinetic energiesthe range of kinetic energies
Section 9.3Section 9.3The Nature of GasesThe Nature of Gases
An increase in the average kinetic An increase in the average kinetic energy of particles causes the energy of particles causes the temperature to rise.temperature to rise. As it cools, the particles tend to move As it cools, the particles tend to move
more slowly, and the average K.E. more slowly, and the average K.E. declines.declines.
Is there a point where they slow down Is there a point where they slow down
enough to enough to stopstop moving? moving?
Section 9.3Section 9.3The Nature of GasesThe Nature of Gases
The particles would have no kinetic The particles would have no kinetic energy at that point, because they energy at that point, because they would have no motionwould have no motion Absolute zeroAbsolute zero (0 K, or –273 (0 K, or –273 ooC) is C) is
the temperature at which the motion the temperature at which the motion of particles of particles theoretically ceasestheoretically ceases
This has never been reached, but This has never been reached, but about 0.5 x 10about 0.5 x 10-9-9 K has been achieved K has been achieved
Section 9.3Section 9.3The Nature of GasesThe Nature of Gases
The Kelvin temperature scale The Kelvin temperature scale reflects a reflects a direct relationshipdirect relationship between temperature and average between temperature and average kinetic energykinetic energyParticles of He gas at 200 K have Particles of He gas at 200 K have
twice the average kinetic energytwice the average kinetic energy as particles of He gas at 100 Kas particles of He gas at 100 K
Section 9.4Section 9.4The Nature of GasesThe Nature of Gases
Solids and liquids differ in their Solids and liquids differ in their response to temperatureresponse to temperature However, at any given temperature the However, at any given temperature the
particles of all substances, regardless of particles of all substances, regardless of their physical state, have the same their physical state, have the same average kinetic energyaverage kinetic energy
What happens to the temperature of a What happens to the temperature of a substance when the average kinetic substance when the average kinetic energy of its particles decreases?energy of its particles decreases?
Section 9.4Section 9.4The Nature of LiquidsThe Nature of Liquids
OBJECTIVES:OBJECTIVES:
IdentifyIdentify factors that factors that determine physical properties determine physical properties of a liquid.of a liquid.
Section 9.4Section 9.4The Nature of LiquidsThe Nature of Liquids
OBJECTIVES:OBJECTIVES:
DefineDefine “evaporation” in “evaporation” in terms of kinetic energy.terms of kinetic energy.
Section 9.4Section 9.4The Nature of LiquidsThe Nature of Liquids
OBJECTIVES:OBJECTIVES:
DescribeDescribe the equilibrium the equilibrium between a liquid and its between a liquid and its vapor.vapor.
Section 9.4Section 9.4The Nature of LiquidsThe Nature of Liquids
OBJECTIVES:OBJECTIVES:
IdentifyIdentify the conditions at the conditions at which boiling occurs.which boiling occurs.
Section 9.4Section 9.4The Nature of LiquidsThe Nature of Liquids
Liquid particlesLiquid particles are also in motion. are also in motion.Liquid particles are free to Liquid particles are free to slide slide
pastpast one another one anotherGases and liquids can both Gases and liquids can both
FLOW, as seen in Fig. 9.7, p. 244FLOW, as seen in Fig. 9.7, p. 244However, liquid particles However, liquid particles are are
attractedattracted to each other, whereas to each other, whereas gases are notgases are not
LiquidLiquid
H2O(l) Water
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 31
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
Section 9.4Section 9.4The Nature of LiquidsThe Nature of Liquids
Particles of a liquid spin and vibrate Particles of a liquid spin and vibrate while they move, thus contributing while they move, thus contributing to their average kinetic energyto their average kinetic energy But, most of the particles But, most of the particles do notdo not have have
enough energy to escape into the enough energy to escape into the gaseous state; they would gaseous state; they would have to have to overcomeovercome their intermolecular their intermolecular attractions with other particlesattractions with other particles
Section 9.4Section 9.4The Nature of LiquidsThe Nature of Liquids
The intermolecular attractions also The intermolecular attractions also reduce the amount of space between reduce the amount of space between particles of a liquidparticles of a liquidThus, liquids are more Thus, liquids are more densedense than than
gasesgases Increasing pressure on liquid has Increasing pressure on liquid has
hardly any effecthardly any effect on it’s on it’s volumevolume
Section 9.5Section 9.5The Nature of LiquidsThe Nature of Liquids
Increasing the pressure also has Increasing the pressure also has little effect on the little effect on the volume of a volume of a solidsolid For that reason, liquids and solids are For that reason, liquids and solids are
known as the known as the condensed states of condensed states of mattermatter
Water in an open vessel or puddle Water in an open vessel or puddle eventually goes into the aireventually goes into the air
Fig. 9.8a – page 244Fig. 9.8a – page 244
Section 9.5Section 9.5The Nature of LiquidsThe Nature of Liquids
The conversion of a liquid to a gas The conversion of a liquid to a gas or vapor is called or vapor is called vaporizationvaporization When this occurs at the When this occurs at the surfacesurface of a of a
liquid that is liquid that is notnot boiling, the process boiling, the process is called is called evaporationevaporation
Some of the particles break away and Some of the particles break away and enter the gas or vapor state; but enter the gas or vapor state; but onlyonly those with the minimum kinetic energythose with the minimum kinetic energy
Section 9.5Section 9.5The Nature of LiquidsThe Nature of Liquids
A liquid will also evaporate faster A liquid will also evaporate faster when heatedwhen heated Because the added heat increases Because the added heat increases
the average kinetic energy needed to the average kinetic energy needed to overcome the attractive forcesovercome the attractive forces
But, evaporation is a But, evaporation is a cooling processcooling process Cooling occurs because those with Cooling occurs because those with
the highest energy escape firstthe highest energy escape first
To evaporate, molecules must have sufficient To evaporate, molecules must have sufficient energy to break IM forces.energy to break IM forces.
Molecules at the surface break away and Molecules at the surface break away and become gas.become gas.
Only those with enough KE escape.Only those with enough KE escape. Breaking IM forces requires energy. The Breaking IM forces requires energy. The
process of evaporation is process of evaporation is endothermicendothermic.. Evaporation is a cooling process.Evaporation is a cooling process. It requires heat.It requires heat.
EvaporationEvaporation
Section 9.5Section 9.5The Nature of LiquidsThe Nature of Liquids
Particles left behind have Particles left behind have lowerlower average kinetic energies; thus the average kinetic energies; thus the temperature decreasestemperature decreases Similar to removing the fastest runner Similar to removing the fastest runner
from a race- the remaining runners from a race- the remaining runners have a lower average speedhave a lower average speed
Evaporation helps to keep our skin Evaporation helps to keep our skin cooler on a hot day, unless it is very cooler on a hot day, unless it is very humid on that day. Why?humid on that day. Why?
Section 9.5Section 9.5The Nature of LiquidsThe Nature of Liquids
Evaporation of a liquid in a closed Evaporation of a liquid in a closed container is somewhat differentcontainer is somewhat different Fig. 9.8b on page 244 shows that no Fig. 9.8b on page 244 shows that no
particles can escape into the outside particles can escape into the outside airair
When some particles do vaporize, When some particles do vaporize, these collide with the walls of the these collide with the walls of the container producing container producing vapor pressurevapor pressure
Section 9.5Section 9.5The Nature of LiquidsThe Nature of Liquids
Eventually, some of the particles will Eventually, some of the particles will return to the liquid, or return to the liquid, or condensecondense
After a while, the number of After a while, the number of particles evaporating will equal the particles evaporating will equal the number condensing- the space number condensing- the space above the liquid is now saturated above the liquid is now saturated with vaporwith vapor A dynamic equilibrium existsA dynamic equilibrium exists Rate of evaporationRate of evaporation = = rate of condensationrate of condensation
When first sealed, the molecules When first sealed, the molecules gradually escape the surface of the gradually escape the surface of the liquid.liquid.
As the molecules build up above the As the molecules build up above the liquid - some condense back to a liquid - some condense back to a liquid.liquid.
The rate at which the molecules The rate at which the molecules evaporate and condense are equal.evaporate and condense are equal.
Dynamic EquilibriumDynamic Equilibrium
As time goes by the rate of vaporization As time goes by the rate of vaporization remains constant but the rate of remains constant but the rate of condensation increases because there condensation increases because there are more molecules to condense.are more molecules to condense.
Equilibrium is reached when:Equilibrium is reached when:Rate of VaporizationRate of Vaporization = = Rate of CondensationRate of Condensation
Molecules are constantly changing phase Molecules are constantly changing phase “dynamic”“dynamic”
`The total amount of liquid and vapor remains constant `The total amount of liquid and vapor remains constant “equilibrium”“equilibrium”
Dynamic EquilibriumDynamic Equilibrium
Section 9.5Section 9.5The Nature of LiquidsThe Nature of Liquids
Note that there will Note that there will stillstill be particles be particles that evaporate and condensethat evaporate and condense But, there will be no But, there will be no NETNET change change
An An increase in temperatureincrease in temperature of a of a contained liquid increases the vapor contained liquid increases the vapor pressure- the particles have an pressure- the particles have an increased kinetic energy, thus more increased kinetic energy, thus more minimum energy to escapeminimum energy to escape
Section 9.5Section 9.5The Nature of LiquidsThe Nature of Liquids
Note Table 9.1, page 246Note Table 9.1, page 246 The vapor pressure of a liquid can The vapor pressure of a liquid can
be determined by a device called a be determined by a device called a “manometer”“manometer”- Figure 9.10, p. 246- Figure 9.10, p. 246
The vapor pressure of the liquid will The vapor pressure of the liquid will push the mercury into the U-tubepush the mercury into the U-tube
A barometer is a type of manometerA barometer is a type of manometer
Section 9.6Section 9.6The Nature of LiquidsThe Nature of Liquids
We now know the rate of We now know the rate of evaporation from an open container evaporation from an open container increases as heat is addedincreases as heat is added The heating allows larger numbers of The heating allows larger numbers of
particles at the liquid’s surface to particles at the liquid’s surface to overcome the attractive forcesovercome the attractive forces
Heating allows the average kinetic Heating allows the average kinetic energy of all particles to increaseenergy of all particles to increase
Section 9.6Section 9.6The Nature of LiquidsThe Nature of Liquids
The The boiling pointboiling point (bp) is the (bp) is the temperature at which the temperature at which the vapor vapor pressure of the liquid is just equal to pressure of the liquid is just equal to the external pressure on the liquidthe external pressure on the liquidBubbles form Bubbles form throughoutthroughout the the
liquid, rise to the surface, and liquid, rise to the surface, and escape into the airescape into the air
Section 9.6Section 9.6The Nature of LiquidsThe Nature of Liquids
Since the boiling point is where the Since the boiling point is where the vapor pressure equals external vapor pressure equals external pressure, the bp changes if the pressure, the bp changes if the external pressure changesexternal pressure changes
Normal boiling pointNormal boiling point-- defined as defined as the bp of a liquid at a pressure of the bp of a liquid at a pressure of 101.3 kPa (or standard pressure)101.3 kPa (or standard pressure)
Section 9.6Section 9.6The Nature of LiquidsThe Nature of Liquids
Normal bp of water = 100 Normal bp of water = 100 ooCC However, in Denver = 95 However, in Denver = 95 ooC, since C, since
Denver is 1600 m above sea level and Denver is 1600 m above sea level and average atmospheric pressure is about average atmospheric pressure is about 85.3 kPa (Recipe adjustments?)85.3 kPa (Recipe adjustments?)
In In pressure cookerspressure cookers, which reduce , which reduce cooking time, water boils cooking time, water boils aboveabove 100 100 ooC C due to the increased pressuredue to the increased pressure
- Page 247
Not Boiling Normal Boiling Point @ 101.3 kPa = 100 oC
Boiling, but @ 34 kPa = 70 oC
Section 9.6Section 9.6The Nature of LiquidsThe Nature of Liquids
AutoclavesAutoclaves, devices often used in the , devices often used in the past to sterilize medical instruments, past to sterilize medical instruments, operated much in a similar way – higher operated much in a similar way – higher pressure, thus higher boiling pointpressure, thus higher boiling point
Boiling is a cooling processBoiling is a cooling process much the much the same as evaporationsame as evaporationThose particles with highest KE Those particles with highest KE
escape firstescape first
Section 9.6Section 9.6The Nature of LiquidsThe Nature of Liquids
Turning down the source of external Turning down the source of external heat drops the liquid’s temperature heat drops the liquid’s temperature below the boiling pointbelow the boiling point
Supplying more heat allows Supplying more heat allows particles to acquire enough KE to particles to acquire enough KE to escape- the escape- the temperature does not temperature does not go above the boiling pointgo above the boiling point, the liquid , the liquid only boils at a faster rateonly boils at a faster rate
- Page 394
Questions:
a. 60 oC b. about 20 kPa c. about 30 kPa
Section 9.7Section 9.7The Nature of SolidsThe Nature of Solids
OBJECTIVES:OBJECTIVES:
EvaluateEvaluate how the way how the way particles are organized particles are organized explains the properties of explains the properties of solids.solids.
Section 9.7Section 9.7The Nature of SolidsThe Nature of Solids
OBJECTIVES:OBJECTIVES:
IdentifyIdentify the factors that the factors that determine the shape of a determine the shape of a crystal.crystal.
Section 9.7Section 9.7The Nature of SolidsThe Nature of Solids
OBJECTIVES:OBJECTIVES:
ExplainExplain how allotropes of an how allotropes of an element are different.element are different.
Section 9.7Section 9.7The Nature of SolidsThe Nature of Solids
Particles in a liquid are relatively Particles in a liquid are relatively free to movefree to moveSolid particles are Solid particles are notnot
Figure 9.14, page 396 shows Figure 9.14, page 396 shows solid particles tend to solid particles tend to vibratevibrate about fixed pointsabout fixed points, rather than , rather than sliding from place to placesliding from place to place
Activity! Matter and Phase Change Activity! Matter and Phase Change Simulator.Simulator. http://http://phet.colorado.eduphet.colorado.edu
/en/simulation/states-of-matter/en/simulation/states-of-matter
Section 9.7Section 9.7The Nature of SolidsThe Nature of Solids
Most solids have particles packed Most solids have particles packed against one another in a highly against one another in a highly organized patternorganized pattern Tend to be dense and incompressibleTend to be dense and incompressible Do not flow, nor take the shape of Do not flow, nor take the shape of
their containertheir container Are still able to move, unless they Are still able to move, unless they
would reach absolute zerowould reach absolute zero
Solid, Liquid, GasSolid, Liquid, Gas
(a) Particles in solid (b) Particles in liquid (c) Particles in gas
SolidSolid
H2O(s) Ice
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 31
IceIce
H2O(s)
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 31
Photograph of ice model Photograph of snowflakes
IcecreamIce
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
When a solid is heated, the particles When a solid is heated, the particles vibrate more rapidly as the kinetic vibrate more rapidly as the kinetic energy increasesenergy increases The organization of particles within The organization of particles within
the solid breaks down, and eventually the solid breaks down, and eventually the solid meltsthe solid melts
The The melting pointmelting point (mp) is the (mp) is the temperature a solid turns to liquidtemperature a solid turns to liquid
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
At the melting point, the disruptive At the melting point, the disruptive vibrations are strong enough to vibrations are strong enough to overcome the interactions holding overcome the interactions holding them in a fixed positionthem in a fixed position Melting point can be reversed by Melting point can be reversed by
cooling the liquid so it cooling the liquid so it freezesfreezes Solid liquidSolid liquid
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
Generally, Generally, most ionic solids have most ionic solids have high melting pointshigh melting points, due to the , due to the relatively strong forces holding them relatively strong forces holding them togethertogether Sodium chloride (an ionic compound) Sodium chloride (an ionic compound)
has a melting point = 801 has a melting point = 801 ooCC Molecular compounds have Molecular compounds have
relatively low melting pointsrelatively low melting points
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
Hydrogen chloride (a molecular Hydrogen chloride (a molecular compound) has a mp = -112 compound) has a mp = -112 ooCC
Not all solids melt- wood and cane Not all solids melt- wood and cane sugar tend to decompose when sugar tend to decompose when heatedheated
Most solid substances are Most solid substances are crystallinecrystalline in structure in structure
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
In a In a crystalcrystal, such as Fig. 9.18, page , such as Fig. 9.18, page 251, the particles (atoms, ions, or 251, the particles (atoms, ions, or molecules) are arranged in a molecules) are arranged in a orderly, repeating, three-orderly, repeating, three-dimensional pattern called a dimensional pattern called a crystal crystal latticelattice
All crystals have a regular shape, All crystals have a regular shape, which reflects their arrangementwhich reflects their arrangement
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
The The type of bondingtype of bonding that exists that exists between the atoms determines the between the atoms determines the melting points of crystalsmelting points of crystals
A crystal has sides, or A crystal has sides, or facesfaces The angles of the faces are a The angles of the faces are a
characteristic of that substance, and characteristic of that substance, and are always the same for a given are always the same for a given sample of that substancesample of that substance
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
Crystals are classified into Crystals are classified into seven seven groupsgroups, which are shown in Fig. , which are shown in Fig. 9.16, page 2509.16, page 250 The 7 crystal systems differ in terms The 7 crystal systems differ in terms
of the angles between the faces, and of the angles between the faces, and in the number of edges of equal in the number of edges of equal length on each facelength on each face
cubic orthorhombic
Rhombohedral
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
The shape of a crystal depends The shape of a crystal depends upon the arrangement of the upon the arrangement of the particles within itparticles within itThe smallest group of particles The smallest group of particles
within a crystal that retains the within a crystal that retains the geometric shape of the crystal is geometric shape of the crystal is known as a known as a unit cellunit cell
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
There are three kinds of unit There are three kinds of unit cells that can make up a cubic cells that can make up a cubic crystal system:crystal system:1. Simple cubic1. Simple cubic2. Body-centered cubic2. Body-centered cubic3. Face-centered cubic3. Face-centered cubic
90o angle
- Page 251
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
Some solid substances can exist in Some solid substances can exist in more than onemore than one form form Elemental carbon is an example, as Elemental carbon is an example, as
shown in Fig. 9.18, page 251shown in Fig. 9.18, page 251 1. 1. DiamondDiamond, formed by great pressure, formed by great pressure 2. 2. GraphiteGraphite, which is in your pencil, which is in your pencil 3. 3. BuckminsterfullereneBuckminsterfullerene (also called (also called
“buckyballs”) arranged in hollow “buckyballs”) arranged in hollow cages like a soccer ballcages like a soccer ball
Allotropes of CarbonAllotropes of Carbon
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
These are called These are called allotropesallotropes of of carbon, because all are made of carbon, because all are made of pure carbon only , and all are solidpure carbon only , and all are solid
AllotropesAllotropes are two or more different are two or more different molecular forms of the same molecular forms of the same element in the same physical stateelement in the same physical state
Not all solids are crystalline, but Not all solids are crystalline, but instead are instead are amorphousamorphous
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
AmorphousAmorphous solids lack an ordered solids lack an ordered internal structureinternal structure Rubber, plastic, and asphalt are all Rubber, plastic, and asphalt are all
amorphous solids- their atoms are amorphous solids- their atoms are randomly arrangedrandomly arranged
Another example is glass- Another example is glass- substances cooled to a rigid state substances cooled to a rigid state without crystallizingwithout crystallizing
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
Glasses are sometimes called Glasses are sometimes called supercooled liquidssupercooled liquids The irregular internal structures of The irregular internal structures of
glasses are intermediate between glasses are intermediate between those of a crystalline solid and a free-those of a crystalline solid and a free-flowing liquidflowing liquid
Do not melt at a definite mp, but Do not melt at a definite mp, but gradually soften when heatedgradually soften when heated
Section 9.7 Section 9.7 The Nature of SolidsThe Nature of Solids
When a crystalline solid is When a crystalline solid is shattered, the fragments tend to shattered, the fragments tend to have the same surface angles as have the same surface angles as the original solidthe original solid
By contrast, when amorphous solids By contrast, when amorphous solids such as glass is shattered, the such as glass is shattered, the fragments have irregular angles and fragments have irregular angles and jagged edgesjagged edges
Section 9.8Section 9.8Changes of StateChanges of State
OBJECTIVES:OBJECTIVES:
IdentifyIdentify the conditions the conditions necessary for sublimation.necessary for sublimation.
Section 9.9Section 9.9Changes of StateChanges of State
OBJECTIVES:OBJECTIVES:
DescribeDescribe how equilibrium how equilibrium conditions are represented conditions are represented in a phase diagram.in a phase diagram.
During the phase change (change of During the phase change (change of state), the temperature stays the same state), the temperature stays the same even though the heat energy changes. even though the heat energy changes. This energy is going into changing This energy is going into changing
the phase and not into raising the the phase and not into raising the temperature. That's why water temperature. That's why water doesn't get hotter as it is boiling. doesn't get hotter as it is boiling. The The temperature remains constant until temperature remains constant until the phase change is complete. the phase change is complete.
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Latent Heat: The energy absorbed or Latent Heat: The energy absorbed or released when a substance changes released when a substance changes its physical state.its physical state.
Heat added
Tem
pera
ture
(o C
)
0
100
MeltingIce
Water
Water VaporBoiling
Latent Latent HeatHeat
Latent Latent HeatHeat
Copyright © 2010 Ryan P. Murphy
Energy Changes Accompanying Phase ChangesEnergy Changes Accompanying Phase Changes
Solid
Liquid
Gas
Melting Freezing
Deposition
CondensationVaporization
Sublimation
Ene
rgy
of s
yste
m
Brown, LeMay, Bursten, Chemistry 2000, page 405
B. Heating CurvesB. Heating Curves
Latent Heat of FusionLatent Heat of Fusion energy required to change from solid to energy required to change from solid to
liquidliquid some attractive forces are brokensome attractive forces are broken
Latent Heat of VaporizationLatent Heat of Vaporization energy required to change from liquid to gasenergy required to change from liquid to gas all attractive forces are brokenall attractive forces are broken EXEX: steam burns, sweating, and… the : steam burns, sweating, and… the
drinking birddrinking bird
Section 9.8 Section 9.8 Changes of StateChanges of State
SublimationSublimation- the change of a - the change of a substance from a solid directly to substance from a solid directly to a vapor, without passing through a vapor, without passing through the liquid statethe liquid stateExamples: iodine (Fig. 13.14, p. Examples: iodine (Fig. 13.14, p.
401); dry ice (-78 401); dry ice (-78 ooC); mothballs; C); mothballs; solid air freshenerssolid air fresheners
Section 9.9Section 9.9Changes of StateChanges of State
The relationship among the solid, The relationship among the solid, liquid, and vapor states (or phases) liquid, and vapor states (or phases) of a substance in a sealed container of a substance in a sealed container are best represented in a single are best represented in a single graph called a graph called a phase diagramphase diagram
Phase diagramPhase diagram- gives the temperature - gives the temperature and pressure at which a substances and pressure at which a substances exists as solid, liquid, or gas (vapor)exists as solid, liquid, or gas (vapor)
Phase changes by Name
Critical Point
Temperature (oC)
Pre
ssu
re (
kPa)
Section 9.9Section 9.9Changes of StateChanges of State
Fig. 9.23, page 256 shows the Fig. 9.23, page 256 shows the phase diagram for waterphase diagram for water Each region represents a pure phaseEach region represents a pure phase Line between regions is where the Line between regions is where the
two phases exist in equilibriumtwo phases exist in equilibriumTriple pointTriple point is where all 3 curves is where all 3 curves
meet, the conditions where all 3 meet, the conditions where all 3 phases exist in equilibrium!phases exist in equilibrium!
- Page 256
Questions:
Section 9.9Section 9.9Changes of StateChanges of State
With a phase diagram, the With a phase diagram, the changes in mp and bp can be changes in mp and bp can be determined with changes in determined with changes in external pressureexternal pressure
What are the variables plotted What are the variables plotted on a phase diagram?on a phase diagram?
The 4The 4thth S State of Matter: tate of Matter: Plasma (p) Plasma (p) Ionized gas that emits electrons.Ionized gas that emits electrons.
Copyright © 2010 Ryan P. Murphy
99.9% of normal matter is Plasma.99.9% of normal matter is Plasma.
99.9% of normal matter is Plasma.99.9% of normal matter is Plasma. STARSSTARS
99.9% of normal matter is Plasma.99.9% of normal matter is Plasma. STARSSTARS So that .1% is the (s),(l),(g) that we are So that .1% is the (s),(l),(g) that we are
made of.made of.