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4.4.114.4.11 BellringerBellringer
Define as many of the following Define as many of the following terms as you can BRIEFLY, terms as you can BRIEFLY, but in but in your own words:your own words:PressurePressureParticlesParticlesEnergyEnergyGas stateGas state
4.4.114.4.11 AgendaAgenda
MondayMonday 13.1 (gases)13.1 (gases)TuesdayTuesday 13.1 (gases)13.1 (gases)WednesdayWednesday 13.2 (liquids)13.2 (liquids)ThursdayThursday report card pick report card pick upup
FridayFriday 13.2 (liquids) 13.2 (liquids) open notes quizopen notes quiz
Section 13.1Section 13.1The Nature of GasesThe Nature of Gases
SWBAT:SWBAT: DescribeDescribe the 3 assumptions of the the 3 assumptions of the
“kinetic theory” as it applies to gases.“kinetic theory” as it applies to gases. InterpretInterpret gas pressure in terms of gas pressure in terms of
kinetic theory.kinetic theory. DefineDefine the relationship between the relationship between
Kelvin temperature and average Kelvin temperature and average kinetic energy.kinetic energy.
Section 13.1Section 13.1The 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 particlestiny particles in in all forms of matterall forms of matter are in are in constant motionconstant motion!!
Section 13.1Section 13.1The 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 13.1Section 13.1The 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 1700 km/h!1700 km/h!
Section 13.1Section 13.1The Nature of GasesThe Nature of Gases
#3#3. Collisions are . Collisions are perfectly perfectly elasticelastic: : meaning KE is meaning KE is transferred without loss from 1 transferred without loss from 1 particle to anotherparticle to another
total kinetic energy total kinetic energy remains constantremains constant
‘‘Elastic collisions’ = Elastic collisions’ = Conservation of Conservation of KINETICKINETIC
energyenergy
Section 13.1Section 13.1The 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 object area of an object Due to: a) Due to: a) forceforce of collisions of collisions, and , and
b) b) numbernumber of collisions of collisions No particles present? Then there No particles present? Then there
cannot be any collisions, and thus cannot be any collisions, and thus no pressure no pressure called a called a vacuumvacuum
Section 13.1Section 13.1The 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 there is less air as elevation because there is less air as elevation increasesincreases
BarometerBarometer is the measuring device is the measuring device for atmospheric pressure, which for atmospheric pressure, which depends on weather & altitudedepends on 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
4.5.114.5.11 Pressure can be measured with Pressure can be measured with
three different units, their relationship three different units, their relationship is shown below:is shown below: 1 atm = 101.3kPa = 760 mm Hg…1 atm = 101.3kPa = 760 mm Hg…
With that information, convert With that information, convert 532 mmHg…532 mmHg… To atmTo atm To kPaTo kPa
Section 13.1Section 13.1The Nature of GasesThe Nature of Gases
Mercury BarometerMercury Barometer – Fig. 13.2, – Fig. 13.2, page 386 – a straight glass tube page 386 – a straight glass tube filled with Hg, and closed at one filled with Hg, and closed at one end; placed in a dish of Hg, with the end; 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 13.1Section 13.1The 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
Sample 13.1, page 387Sample 13.1, page 387 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 moleculesnumber of collisions of air molecules
Section 13.1Section 13.1The 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 13.1Section 13.1The 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 energy is storedSome energy is stored within the within the
particles particles potential energypotential energy Remaining energy speeds up the Remaining energy speeds up the
particles (increases average kinetic particles (increases average kinetic energy)- & energy)- & temperaturetemperature
Section 13.1Section 13.1The 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 13.1Section 13.1The Nature of GasesThe Nature of Gases
An increase in the average kinetic energy of An increase in the average kinetic energy of particles causes the temperature to rise.particles causes the temperature to rise. As it cools, the particles tend to move more As it cools, the particles tend to move more
slowly, and the average K.E. declines.slowly, and the average K.E. declines. Is there a point where they slow down enough Is there a point where they slow down enough
to to stopstop moving? moving? Absolute zeroAbsolute zero (0 K, or –273 (0 K, or –273 ooC) is the C) is the
temperature at which the motion of particles temperature at which the motion of particles theoretically ceasestheoretically ceases
Bellringer: 4.6.11Bellringer: 4.6.11 Fill in the following chart:Fill in the following chart:
Agenda:BR Review of Gases LiquidsHW Have 13.1, 13.2 notes AND the 13.1 questions done for FRIDAY; 13.3 AND 13.4 NOTES FOR TUE
STATE SOLID LIQUID GAS
KINETIC ENERGY(LOW/MEDIUM/HIGH)
ATTRACTION BETWEEN PARTICLES?(LOW/MEDIUM/HIGH)
CAN PARTICLES MOVE FREELY?
DENSITY?
DEFINITE SHAPE?
CAN IT BE COMPRESSED?
Bellringer: 4.6.11Bellringer: 4.6.11 Fill in the following chart:Fill in the following chart:
Agenda:BR Review of Gases LiquidsHW Have 13.1, 13.2 notes AND the 13.1 questions done for FRIDAY; 13.3 AND 13.4 NOTES FOR TUE
STATE SOLID LIQUID GAS
KINETIC ENERGY(LOW/MEDIUM/HIGH)
LOW MED HIGH
ATTRACTION BETWEEN PARTICLES?(LOW/MEDIUM/HIGH)
CAN PARTICLES MOVE FREELY?
DENSITY?
DEFINITE SHAPE?
CAN IT BE COMPRESSED?
Bellringer: 4.6.11Bellringer: 4.6.11 Fill in the following chart:Fill in the following chart:
Agenda:BR Review of Gases LiquidsHW Have 13.1, 13.2 notes AND the 13.1 questions done for FRIDAY; 13.3 AND 13.4 NOTES FOR TUE
STATE SOLID LIQUID GAS
KINETIC ENERGY(LOW/MEDIUM/HIGH)
LOW MED HIGH
ATTRACTION BETWEEN PARTICLES?(LOW/MEDIUM/HIGH)
HIGH MED LOW
CAN PARTICLES MOVE FREELY?
DENSITY?
DEFINITE SHAPE?
CAN IT BE COMPRESSED?
Bellringer: 4.6.11Bellringer: 4.6.11 Fill in the following chart:Fill in the following chart:
Agenda:BR Review of Gases LiquidsHW Have 13.1, 13.2 notes AND the 13.1 questions done for FRIDAY; 13.3 AND 13.4 NOTES FOR TUE
STATE SOLID LIQUID GAS
KINETIC ENERGY(LOW/MEDIUM/HIGH)
LOW MED HIGH
ATTRACTION BETWEEN PARTICLES?(LOW/MEDIUM/HIGH)
HIGH MED LOW
CAN PARTICLES MOVE FREELY?
NO CAN MOVE BUT STAY CLOSE
YES, ANYWHERE
DENSITY?
DEFINITE SHAPE?
CAN IT BE COMPRESSED?
Bellringer: 4.6.11Bellringer: 4.6.11 Fill in the following chart:Fill in the following chart:
Agenda:BR Review of Gases LiquidsHW Have 13.1, 13.2 notes AND the 13.1 questions done for FRIDAY; 13.3 AND 13.4 NOTES FOR TUE
STATE SOLID LIQUID GAS
KINETIC ENERGY(LOW/MEDIUM/HIGH)
LOW MED HIGH
ATTRACTION BETWEEN PARTICLES?(LOW/MEDIUM/HIGH)
HIGH MED LOW
CAN PARTICLES MOVE FREELY?
NO CAN MOVE BUT STAY CLOSE
YES, ANYWHERE
DENSITY? HIGH MED-HIGH VERY LOW
DEFINITE SHAPE?
CAN IT BE COMPRESSED?
Bellringer: 4.6.11Bellringer: 4.6.11 Fill in the following chart:Fill in the following chart:
Agenda:BR Review of Gases LiquidsHW Have 13.1, 13.2 notes AND the 13.1 questions done for FRIDAY; 13.3 AND 13.4 NOTES FOR TUE
STATE SOLID LIQUID GAS
KINETIC ENERGY(LOW/MEDIUM/HIGH)
LOW MED HIGH
ATTRACTION BETWEEN PARTICLES?(LOW/MEDIUM/HIGH)
HIGH MED LOW
CAN PARTICLES MOVE FREELY?
NO CAN MOVE BUT STAY CLOSE
YES, ANYWHERE
DENSITY? HIGH MED-HIGH VERY LOW
DEFINITE SHAPE?
YES NO NO
CAN IT BE COMPRESSED?
Bellringer: 4.6.11Bellringer: 4.6.11 Fill in the following chart:Fill in the following chart:
Agenda:BR Review of Gases LiquidsHW Have 13.1, 13.2 notes AND the 13.1 questions done for FRIDAY; 13.3 AND 13.4 NOTES FOR TUE
STATE SOLID LIQUID GAS
KINETIC ENERGY(LOW/MEDIUM/HIGH)
LOW MED HIGH
ATTRACTION BETWEEN PARTICLES?(LOW/MEDIUM/HIGH)
HIGH MED LOW
CAN PARTICLES MOVE FREELY?
NO CAN MOVE BUT STAY CLOSE
YES, ANYWHERE
DENSITY? HIGH MED-HIGH VERY LOW
DEFINITE SHAPE?
YES NO NO
CAN IT BE COMPRESSED?
NO NO YES
4.6.114.6.11
Bellringer:Bellringer: In your own words, describe In your own words, describe the differences between the differences between gases, liquids, and solids gases, liquids, and solids (focus on their (focus on their atoms/molecules if possible)atoms/molecules if possible)
What is theWhat is thetemp rangetemp rangeof Hof H22O?O?
What is the What is the difference in difference in
temp. of a temp. of a lowlowboil or a boil or a highhighboil?boil?
What is the What is the COLDESTCOLDESTtemperaturetemperaturepossible? possible? (no heat)(no heat)
Question: How do the shapes of these Question: How do the shapes of these curves differ? curves differ?
(grey is when particles have reached (grey is when particles have reached Emin, the minimum Energy to go from Emin, the minimum Energy to go from
liquidliquidgas)gas)
Answer: As you heat a sample, the curve Answer: As you heat a sample, the curve becomes wider and shorter, there is a becomes wider and shorter, there is a
broader RANGE of KE values, and more broader RANGE of KE values, and more can go from liquidcan go from liquid gas gas
Section 13.2Section 13.2The 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.
DefineDefine “evaporation” in terms “evaporation” in terms of kinetic energy.of kinetic energy.
Section 13.2Section 13.2The 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.
IdentifyIdentify the conditions at the conditions at which boiling occurs.which boiling occurs.
Section 13.2Section 13.2The Nature of LiquidsThe Nature of Liquids
Liquid particlesLiquid particles (like gases) are also (like gases) are also in motion.in motion.But liquid particles But liquid particles slide pastslide past each each
otherotherGases and liquids can both Gases and liquids can both
FLOW, as seen in Fig. 13.5, p.390FLOW, as seen in Fig. 13.5, p.390Important Important Liquid particles Liquid particles are are
attractedattracted to each other, gases are not!! to each other, gases are not!!
Section 13.2Section 13.2The 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 to while they move, thus contributing to their average kinetic energytheir average kinetic energy But, most particles But, most particles do notdo not have enough have enough
energy to escape into the gas state; energy to escape into the gas state; they would they would have to overcomehave to overcome their their intermolecular attractions with other intermolecular attractions with other particles (remember the KE curves)particles (remember the KE curves)
Section 13.2Section 13.2The 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 liquidSo, liquids are more So, liquids are more densedense than than
gasesgases Increasing pressure on a liquid or Increasing pressure on a liquid or
solid has solid has hardly any effecthardly any effect on it’s on it’s volumevolume
Section 13.2Section 13.2The 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 enough kinetic energythose with enough kinetic energy
Section 13.2Section 13.2The 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 the Because the added heat increases the
average kinetic energy needed to 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 the particles Cooling occurs because the particles
with the highest energy escape firstwith the highest energy escape first
Section 13.2Section 13.2The 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 13.2Section 13.2The 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. 13.6b on page 391 shows that no Fig. 13.6b on page 391 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 13.2Section 13.2The 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
Section 13.2Section 13.2The 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 13.2Section 13.2The Nature of LiquidsThe Nature of Liquids
Note Table 13.1, page 392Note Table 13.1, page 392 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 13.7, p.393- Figure 13.7, p.393
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 13.2Section 13.2The 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 13.2Section 13.2The 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 13.2Section 13.2The 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 13.2Section 13.2The 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
Section 13.2Section 13.2The 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 13.2Section 13.2The 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
Section 13.3Section 13.3The 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 13.3Section 13.3The 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 13.3Section 13.3The Nature of SolidsThe Nature of Solids
OBJECTIVES:OBJECTIVES:
ExplainExplain how allotropes of an how allotropes of an element are different.element are different.
Section 13.3Section 13.3The 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 13.10, page 396 shows Figure 13.10, 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
Section 13.3Section 13.3The 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 would reach absolute zeroabsolute zero
Section 13.3Section 13.3The 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 13.3Section 13.3The 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 13.3Section 13.3The 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 13.3Section 13.3The 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 13.3Section 13.3The Nature of SolidsThe Nature of Solids
In a In a crystalcrystal, such as Fig. 13.10, , such as Fig. 13.10, page 396, the particles (atoms, page 396, the particles (atoms, ions, or molecules) are arranged in ions, or molecules) are arranged in a orderly, repeating, three-a 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 13.3Section 13.3The 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 13.3Section 13.3The 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. 13.11, page 39713.11, page 397 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
Section 13.3Section 13.3The 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 13.3Section 13.3The 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
Section 13.3Section 13.3The 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. 13.13, page 399shown in Fig. 13.13, page 399 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
Section 13.3Section 13.3The 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 13.3Section 13.3The 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 13.3Section 13.3The 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 13.3Section 13.3The 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 13.4Section 13.4Changes of StateChanges of State
OBJECTIVES:OBJECTIVES:
IdentifyIdentify the conditions the conditions necessary for sublimation.necessary for sublimation.
Section 13.4Section 13.4Changes 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.
Section 13.4Section 13.4Changes 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 13.4Section 13.4Changes of StateChanges of State
Sublimation is useful in situations such Sublimation is useful in situations such as as freeze-dryingfreeze-drying foods- such as by foods- such as by freezing the freshly brewed coffee, and freezing the freshly brewed coffee, and then removing the water vapor by a then removing the water vapor by a vacuum pumpvacuum pump
Also useful in separating substances - Also useful in separating substances - organic chemists use it separate organic chemists use it separate mixtures and purify materialsmixtures and purify materials
Section 13.4Section 13.4Changes 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)
Section 13.4Section 13.4Changes of StateChanges of State
Fig. 13.15, page 403 shows the Fig. 13.15, page 403 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!
Section 13.4Section 13.4Changes 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?