View
216
Download
0
Category
Preview:
Citation preview
KINETIC THEORYKINETIC THEORY
Unit 7Unit 7
ChemistryChemistry
LangleyLangley
*Corresponds to Chapter 13 (pgs. 384-409) in Prentice Hall Chemistry textbook
KINETIC THEORYKINETIC THEORY
Kinetic Theory states that the tiny Kinetic Theory states that the tiny particles in all forms of matter are in particles in all forms of matter are in constant motion.constant motion. Kinetic refers to motionKinetic refers to motion Helps you understand the behavior of solid, Helps you understand the behavior of solid,
liquid, and gas atoms/molecules as well as liquid, and gas atoms/molecules as well as the physical propertiesthe physical properties
Provides a model behavior based off three Provides a model behavior based off three principalsprincipals
KINETIC THEORYKINETIC THEORY
3 Principles of Kinetic Theory3 Principles of Kinetic Theory All matter is made of tiny particles (atoms)All matter is made of tiny particles (atoms) These particles are in constant motionThese particles are in constant motion When particles collide with each other or When particles collide with each other or
the container, the collisions are perfectly the container, the collisions are perfectly elastic (no energy is lost)elastic (no energy is lost)
STATES OF MATTERSTATES OF MATTER
5 States of Matter5 States of Matter SolidSolid LiquidLiquid GasGas PlasmaPlasma Bose-EinsteinBose-Einstein
CondensatesCondensates
http://www.plasmas.org/E-4phases2.jpg
SOLIDSSOLIDS
Particles are tightly packed and close togetherParticles are tightly packed and close together Particles do move but not very muchParticles do move but not very much Definite shape and definite volume (because Definite shape and definite volume (because
particles are packed closely and do not move)particles are packed closely and do not move) Most solids are crystalsMost solids are crystals Crystals are made of unit cells (repeating Crystals are made of unit cells (repeating
patterns)patterns) The shape of a crystal reflects the arrangement of The shape of a crystal reflects the arrangement of
the particles within the solidthe particles within the solid
SOLIDSSOLIDS
Unit cells put together make a crystal Unit cells put together make a crystal lattice (skeleton for the crystal)lattice (skeleton for the crystal)
Crystals are classified into seven crystal Crystals are classified into seven crystal systems: cubic, tetragonal, systems: cubic, tetragonal, orthorhombic, monoclinic, triclinic, orthorhombic, monoclinic, triclinic, hexagonal, rhombohedralhexagonal, rhombohedral
Unit cell Unit cell crystal lattice crystal lattice solid solid
SOLIDSSOLIDS Amorphous Solid:Amorphous Solid:
A solid with no defined shape (not a crystal)A solid with no defined shape (not a crystal) A solid that lacks an ordered internal structureA solid that lacks an ordered internal structure Examples: Clay, PlayDoh, Rubber, Glass, Plastic, Examples: Clay, PlayDoh, Rubber, Glass, Plastic,
AsphaltAsphalt Allotropes:Allotropes:
Solids that appear in more than one formSolids that appear in more than one form 2 or more different molecular forms of the same 2 or more different molecular forms of the same
element in the same physical state (have different element in the same physical state (have different properties)properties)
Example: CarbonExample: Carbon Powder = GraphitePowder = Graphite Pencil “lead” = graphitePencil “lead” = graphite Hard solid = diamondHard solid = diamond
SOLIDSSOLIDS
www.ohsu.edu/research/sbh/resultsimages/crystalvsglass.gif
SOLIDSSOLIDSAllotropes of Carbon: a) diamond, b) graphite, c) lonsdaleite, d)buckminsterfullerene (buckyball), e) C540, f) C70, g) amorphous carbon, and h) single-walled (buckytube)
www.wikipedia.org
LIQUIDSLIQUIDS
Particles are spread apartParticles are spread apart Particles move slowly through a containerParticles move slowly through a container No definite shape but do have a definite No definite shape but do have a definite
volumevolume Flow from one container to anotherFlow from one container to another Viscosity – resistance of a liquid to flowingViscosity – resistance of a liquid to flowing
Honey – high viscosityHoney – high viscosity Water – low viscosityWater – low viscosity
chemed.chem.purdue.edu/.../graphics
GASESGASES
Particles are very far apartParticles are very far apart Particles move very fastParticles move very fast No definite shape and No definite volumeNo definite shape and No definite volume
http://www.phy.cuhk.edu.hk/contextual/heat/tep/trans/kinetic_theory.gif
PLASMAPLASMA
Particles are extremely far apartParticles are extremely far apart Particles move extremely fastParticles move extremely fast Only exists above 3000 degrees CelsiusOnly exists above 3000 degrees Celsius Basically, plasma is a hot gasBasically, plasma is a hot gas When particles collide, they break apart When particles collide, they break apart
into protons, neutrons, and electronsinto protons, neutrons, and electrons Occurs naturally on the sun and starsOccurs naturally on the sun and stars
BOSE-EINSTEIN CONDENSATEBOSE-EINSTEIN CONDENSATE
Particles extremely close togetherParticles extremely close together Particles barely moveParticles barely move Only found at extremely cold Only found at extremely cold
temperaturestemperatures Basically Bose-Einstein is a cold solidBasically Bose-Einstein is a cold solid Lowest energy of the 5 states/phases of Lowest energy of the 5 states/phases of
mattermatter
GASES AND PRESSUREGASES AND PRESSURE
Gas pressure is the force exerted by a gas per unit Gas pressure is the force exerted by a gas per unit surface area of an objectsurface area of an object Force and number of collisionsForce and number of collisions When there are no particles present, no collisions = no When there are no particles present, no collisions = no
pressure = vacuumpressure = vacuum Atmospheric Pressure is caused by a mixuture of gases Atmospheric Pressure is caused by a mixuture of gases
(i.e. the air)(i.e. the air) Results from gravity holding air molecules downward in/on Results from gravity holding air molecules downward in/on
the Earth’s atmosphere; atmospheric pressure decreases the Earth’s atmosphere; atmospheric pressure decreases with altitude, increases with depthwith altitude, increases with depth
Barometers are devices used to measure atmospheric Barometers are devices used to measure atmospheric pressure (contains mercury)pressure (contains mercury)
Standard Pressure is average normal pressure at sea Standard Pressure is average normal pressure at sea levellevel As you go ABOVE sea level, pressure is lessAs you go ABOVE sea level, pressure is less As you go BELOW sea level, pressure is greaterAs you go BELOW sea level, pressure is greater
GASES AND PRESSUREGASES AND PRESSURE
Standard Pressure Values Standard Pressure Values At sea level the pressure can be recorded as: At sea level the pressure can be recorded as:
14.7 psi (pounds per square inch)14.7 psi (pounds per square inch) 29.9 inHg (inches of Mercury)29.9 inHg (inches of Mercury) 760 mmHg (millimeters of Mercury)760 mmHg (millimeters of Mercury) 760 torr760 torr 1 atm (atmosphere)1 atm (atmosphere) 101.325 kPa (kilopascals)101.325 kPa (kilopascals)
All of these values are EQUAL to each other:All of these values are EQUAL to each other: 29.9 inHg = 101.325 kPa29.9 inHg = 101.325 kPa 760 torr = 760 mmHg760 torr = 760 mmHg 1 atm = 14.7 psi1 atm = 14.7 psi and so on……….and so on……….
Say Say hellohello to Factor Label Method!!!!!!!!!!!! to Factor Label Method!!!!!!!!!!!!
GASES AND PRESSUREGASES AND PRESSURE
STPSTP Standard Temperature and PressureStandard Temperature and Pressure Standard Pressure values are the values listed on Standard Pressure values are the values listed on
the previous slidesthe previous slides Standard Temperature is 0°C Standard Temperature is 0°C oror 273 K 273 K
If temperature is given to you in Farenheit, must convert If temperature is given to you in Farenheit, must convert first!first!
°F = (9/5)°C + 32°F = (9/5)°C + 32 °C = (5(°F-32)) / 9 Remember order of operation rules°C = (5(°F-32)) / 9 Remember order of operation rules K = 273 + °CK = 273 + °C °C = K – 273°C = K – 273
GASES AND PRESSUREGASES AND PRESSURE
Pressure ConversionsPressure Conversions Example 1: 421 torr = ? AtmExample 1: 421 torr = ? Atm
Step 1: Write what you knowStep 1: Write what you know Step 2: Draw the fence and place the given in Step 2: Draw the fence and place the given in
the top leftthe top left Step 3: Arrange what you know from step 1 such Step 3: Arrange what you know from step 1 such
that the nondesired units canceling out so that that the nondesired units canceling out so that you are only left with the units you want (i.e. atm)you are only left with the units you want (i.e. atm)
Step 4: SolveStep 4: Solve Step 5: Report final answer taking into account Step 5: Report final answer taking into account
the appropriate significant figuresthe appropriate significant figures
GASES AND PRESSUREGASES AND PRESSURE
Pressure ConversionsPressure Conversions Example 2: 32.0 psi = ? torrExample 2: 32.0 psi = ? torr
TEMPERATURETEMPERATURE
Temperature is the measure of the average Temperature is the measure of the average kinetic energy of the particles.kinetic energy of the particles.
3 Units for Temperature:3 Units for Temperature: CelsiusCelsius FarenheitFarenheit KelvinKelvin
Has an absolute zeroHas an absolute zero Absolute lowest possible temperatureAbsolute lowest possible temperature All particles would completely stop movingAll particles would completely stop moving
Temperature Conversions:Temperature Conversions: Example 1: Convert 35°C to °FExample 1: Convert 35°C to °F Example 2: Convert 300 Kelvin to °C Example 2: Convert 300 Kelvin to °C
MEASURING PRESSUREMEASURING PRESSURE
Manometers:Manometers: Measure pressureMeasure pressure 2 kinds: open and closed2 kinds: open and closed
Open Manometers:Open Manometers: Compare gas pressure to air pressureCompare gas pressure to air pressure Example: tire gaugeExample: tire gauge
Closed Manometer:Closed Manometer: Directly measure the pressure (no Directly measure the pressure (no
comparison)comparison) Example: barometerExample: barometer
KINETIC ENERGY AND KINETIC ENERGY AND TEMPERATURETEMPERATURE
Energy of motionEnergy of motion Energy of a moving objectEnergy of a moving object Matter is made of particles in motionMatter is made of particles in motion Particles have kinetic energyParticles have kinetic energy KE = (mvKE = (mv22)/2)/2
OROR KE = (ma)/2KE = (ma)/2 Kinetic Energy is measured in Joules Kinetic Energy is measured in Joules
1 J = 1kg1 J = 1kg•m•m22/s/s22
The mass must be in kgThe mass must be in kg The velocity must be in m/s OR acceleration must be in The velocity must be in m/s OR acceleration must be in
mm22/s/s22
KINETIC ENERGY AND KINETIC ENERGY AND TEMPERATURETEMPERATURE
Calculate the KE of a car with a mass of Calculate the KE of a car with a mass of 1500 kg and a speed of 50 m/s 1500 kg and a speed of 50 m/s
KINETIC ENERGY AND KINETIC ENERGY AND TEMPERATURETEMPERATURE
Calculate the KE of a car with a mass of Calculate the KE of a car with a mass of 6780 grams and a speed of 36 km/h6780 grams and a speed of 36 km/h
KINETIC ENERGY AND KINETIC ENERGY AND TEMPERATURETEMPERATURE
Temperature-measure of the average kinetic Temperature-measure of the average kinetic energy of the particles energy of the particles
Kelvin Scale:Kelvin Scale: Has an absolute zero (0K)Has an absolute zero (0K) Absolute lowest possible temperatureAbsolute lowest possible temperature In theory, all particles would completely stop movingIn theory, all particles would completely stop moving
Speed of Gases:Speed of Gases: If two gases have the same temperature (particles If two gases have the same temperature (particles
moving at the same speed) how can you tell which moving at the same speed) how can you tell which gas has a greater speed?gas has a greater speed? The only difference is mass!The only difference is mass! To find mass, use the periodic table To find mass, use the periodic table
KINETIC ENERGY AND KINETIC ENERGY AND TEMPERATURETEMPERATURE
Speed of GasesSpeed of Gases Example 1: If CHExample 1: If CH44 and NH and NH33 are both at 284 are both at 284
K, which gas has a greater speed?K, which gas has a greater speed? Step One: Add up the mass of each gas using Step One: Add up the mass of each gas using
the periodic table.the periodic table. Step Two: The lighter gas moves faster (think Step Two: The lighter gas moves faster (think
about a race between a 100-pound man and a about a race between a 100-pound man and a 700-pound man, the lighter man would move 700-pound man, the lighter man would move faster)faster)
Example 2: Which gas has a faster speed Example 2: Which gas has a faster speed between Brbetween Br22 and CO and CO22 if both are at 32°F? if both are at 32°F?
TERMINOLOGY for PHASE TERMINOLOGY for PHASE CHANGESCHANGES
Melting-commonly used to indicate changing Melting-commonly used to indicate changing from solid to liquidfrom solid to liquid Normal melting point-The temperature at which the Normal melting point-The temperature at which the
vapor pressure of the solid and the vapor pressure vapor pressure of the solid and the vapor pressure of the liquid are equalof the liquid are equal
Freezing-Changing from a liquid to a solidFreezing-Changing from a liquid to a solid Melting and freezing occur at the same Melting and freezing occur at the same
temperature temperature Liquifaction-Turning a gas to a liquidLiquifaction-Turning a gas to a liquid
Only happens in low temperature and high pressure Only happens in low temperature and high pressure situationssituations
TERMINOLOGY for PHASE TERMINOLOGY for PHASE CHANGESCHANGES
Difference in Gas and VaporDifference in Gas and Vapor Gas-state of matter that exists at normal room Gas-state of matter that exists at normal room
temperaturetemperature Vaport-produced by particles escaping from a state Vaport-produced by particles escaping from a state
of matter that is normally liquid or solid at room of matter that is normally liquid or solid at room temperaturetemperature
Boiling-used to indicate changing from a liquid Boiling-used to indicate changing from a liquid to a gas/vaporto a gas/vapor Normal boiling point - temperature at which the Normal boiling point - temperature at which the
vapor pressure of the liquid is equal to standard vapor pressure of the liquid is equal to standard atmospheric pressure, which is atmospheric pressure, which is 101.325 kPa101.325 kPa
Boiling point is a function of pressure. Boiling point is a function of pressure. At lower pressures, the boiling point is lower At lower pressures, the boiling point is lower
TERMINOLOGY for PHASE TERMINOLOGY for PHASE CHANGESCHANGES
2 types of boiling: boiling and 2 types of boiling: boiling and evaporationevaporation
Evaporation takes place only at the surface of a Evaporation takes place only at the surface of a liquid or solid while boiling takes place throughout liquid or solid while boiling takes place throughout the body of a liquid the body of a liquid
Particles have high kinetic energyParticles have high kinetic energy Particles escape and become vaporParticles escape and become vapor
Condensation-used to indicate changing Condensation-used to indicate changing from a vapor to a liquidfrom a vapor to a liquid
TERMINOLOGY for PHASE TERMINOLOGY for PHASE CHANGESCHANGES
Sublimation - when a substance changes directly from Sublimation - when a substance changes directly from a solid to a vapora solid to a vapor The best known example is "dry ice", solid COThe best known example is "dry ice", solid CO22
Deposition-when a substance changes directly from a Deposition-when a substance changes directly from a vapor to a solid (opposite of sublimation)vapor to a solid (opposite of sublimation) Example-formation of frostExample-formation of frost
Dynamic equilibriumDynamic equilibrium - w - when a vapor is in equilibrium hen a vapor is in equilibrium with its liquid as one molecule leaves the liquid to with its liquid as one molecule leaves the liquid to become a vapor, another molecule leaves the vapor to become a vapor, another molecule leaves the vapor to become a liquid. An equal number of molecules will be become a liquid. An equal number of molecules will be found moving in both directionsfound moving in both directions Equilibrium - When there is no net change in a systemEquilibrium - When there is no net change in a system
TERMINOLOGY for PHASE TERMINOLOGY for PHASE CHANGESCHANGES
Points to Know:Points to Know: Melting Point-Temperature when solid turns to a Melting Point-Temperature when solid turns to a
liquidliquid Freezing Point-Temperature when liquid turns to a Freezing Point-Temperature when liquid turns to a
solidsolid Boling Point-Temperature when a liquid turns to a Boling Point-Temperature when a liquid turns to a
vaporvapor Doesn’t boil unitl vapor pressure coming off liquid is equal Doesn’t boil unitl vapor pressure coming off liquid is equal
to the air pressure around itto the air pressure around it Since air pressure changes with height, water does not Since air pressure changes with height, water does not
always boil at 100°Calways boil at 100°C Condensing Point-Tempeature when vapor turns to Condensing Point-Tempeature when vapor turns to
liquidliquid
ENTROPYENTROPY
A measure of the disorder of a systemA measure of the disorder of a system Systems tend to go from a state of order (low Systems tend to go from a state of order (low
entropy) to a state of maximum disorder (high entropy) to a state of maximum disorder (high entropy)entropy)
Entropy of a gas is greater than that of a liquid; Entropy of a gas is greater than that of a liquid; entropy of a liquid is greater than that of a solidentropy of a liquid is greater than that of a solid Solids=low entropy; plasma=high entropySolids=low entropy; plasma=high entropy
Entropy tends to increase when temperature Entropy tends to increase when temperature increasesincreases As substances change from one state to another, As substances change from one state to another,
entropy may increase or decreaseentropy may increase or decrease
Le CHATELIER’S PRINCIPLELe CHATELIER’S PRINCIPLE
Anytime stress is placed on a system, the Anytime stress is placed on a system, the sytem will readjust to accommodate that stresssytem will readjust to accommodate that stress
If a chemical system at equilibrium experiences If a chemical system at equilibrium experiences a change in concentration, temperature, a change in concentration, temperature, volume, or total pressure, then the equilibrium volume, or total pressure, then the equilibrium shifts to partially counteract the imposed shifts to partially counteract the imposed changechange
Can be used to predict the effect of a change Can be used to predict the effect of a change in conditions on a chemical equilibriumin conditions on a chemical equilibrium
Is used by chemists in order to manipulate the Is used by chemists in order to manipulate the outcomes of reversible reactions, often to outcomes of reversible reactions, often to increase the yield of reactions increase the yield of reactions
Le CHATELIER’S PRINCIPLELe CHATELIER’S PRINCIPLE
When liquids are heated (stress) they When liquids are heated (stress) they produce vapor particles (adjust)produce vapor particles (adjust)
When liquids are cooled (stress) the When liquids are cooled (stress) the particles inside tighten to form a solid particles inside tighten to form a solid (adjust)(adjust)
Le CHATELIER’S PRINCIPLELe CHATELIER’S PRINCIPLE
Le Chatelier’s Principle explaining boiling and Le Chatelier’s Principle explaining boiling and condensation using covered beaker partially filled with condensation using covered beaker partially filled with waterwater At a given temperature the covered beaker constitutes a At a given temperature the covered beaker constitutes a
system in which the liquid water is in equilibrium with the water system in which the liquid water is in equilibrium with the water vapor that forms above the surface of the liquid. vapor that forms above the surface of the liquid.
While some molecules of liquid are absorbing heat and While some molecules of liquid are absorbing heat and evaporating to become vapor, an equal number of vapor evaporating to become vapor, an equal number of vapor molecules are giving up heat and condensing to become molecules are giving up heat and condensing to become liquid. liquid.
If stress is put on the system by raising the temperature, then If stress is put on the system by raising the temperature, then according to Le Châtelier's principle the rate of evaporation will according to Le Châtelier's principle the rate of evaporation will exceed the rate of condensation until a new equilibrium is exceed the rate of condensation until a new equilibrium is established established
PHASE DIAGRAMSPHASE DIAGRAMS
A diagram showing the conditions at A diagram showing the conditions at which substance exists as a solid, liquid, which substance exists as a solid, liquid, or vaporor vapor
Shows the temperature and pressure Shows the temperature and pressure required for the 3 states of matter to existrequired for the 3 states of matter to exist
Conditions of pressure and temperature Conditions of pressure and temperature at which two phases exist in equilibrium at which two phases exist in equilibrium are indicated on a phase diagram by a are indicated on a phase diagram by a line separating the phasesline separating the phases
Draw the phase diagram for waterDraw the phase diagram for water
PHASE DIAGRAM-WATERPHASE DIAGRAM-WATER
PHASE DIAGRAM-WATERPHASE DIAGRAM-WATER
Explanation of Phase Diagram:Explanation of Phase Diagram: X axis-Temperature (°C)X axis-Temperature (°C) Y axis- Pressure (kPa)Y axis- Pressure (kPa) Line AB – line of sublimationLine AB – line of sublimation Line BD – boiling point lineLine BD – boiling point line Line BC – melting point lineLine BC – melting point line Point B – triple point (all 3 states of matter Point B – triple point (all 3 states of matter
exist at the same time)exist at the same time) TTmm – melting point at standard pressure – melting point at standard pressure TTbb – boiling point at standard pressure – boiling point at standard pressure
HEAT in CHANGES of HEAT in CHANGES of STATESTATE
Energy Diagrams (also referred to as Energy Diagrams (also referred to as Heating Curves)Heating Curves) Graphically describes the enthalpy (the heat Graphically describes the enthalpy (the heat
content of a system at sonstant pressure) content of a system at sonstant pressure) changes that take place during phase changes that take place during phase changeschanges
X axis is Energy (Heat supplied)X axis is Energy (Heat supplied) Y axis is TemperatureY axis is Temperature
HEAT in CHANGES of HEAT in CHANGES of STATESTATE
Constructing Energy DiagramsConstructing Energy Diagrams Step 1: Determine/Identify the melting and boiling Step 1: Determine/Identify the melting and boiling
points for the specified substancepoints for the specified substance Step 2: Draw x and y axis (energy vs temp)Step 2: Draw x and y axis (energy vs temp) Step 3: CalculationsStep 3: Calculations
First diagonal line: Q = mcFirst diagonal line: Q = mcTT First horizontal line: Q = mHFirst horizontal line: Q = mHff
Second diagonal line: Q = mcSecond diagonal line: Q = mcTT Second horizontal line: Q = mHSecond horizontal line: Q = mHvv
Third horizontal line: Q = mcThird horizontal line: Q = mcTT Add up all values!!!Add up all values!!!
Draw the energy diagram for 10 grams of water Draw the energy diagram for 10 grams of water as it goes from –25°C to 140°C as it goes from –25°C to 140°C
Recommended