KINETIC THEORY

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KINETIC THEORY

• Unit 7
• Chemistry
• Langley

Corresponds to Chapter 13 (pgs. 384-409) in
Prentice Hall Chemistry textbook
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KINETIC THEORY

• Kinetic Theory states that the tiny particles in
  all forms of matter are in constant motion.
• Kinetic refers to motion
• Helps you understand the behavior of solid,
  liquid, and gas atoms/molecules as well as the
  physical properties
• Provides a model behavior based off three
  principals

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KINETIC THEORY

• 3 Principles of Kinetic Theory
• All matter is made of tiny particles (atoms)
• These particles are in constant motion
• When particles collide with each other or the
  container, the collisions are perfectly elastic
  (no energy is lost)

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STATES OF MATTER

• 5 States of Matter
• Solid
• Liquid
• Gas
• Plasma
• Bose-Einstein
• Condensates

http//www.plasmas.org/E-4phases2.jpg
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SOLIDS

• Particles are tightly packed and close together
• Particles do move but not very much
• Definite shape and definite volume (because
  particles are packed closely and do not move)
• Most solids are crystals
• Crystals are made of unit cells (repeating
  patterns)
• The shape of a crystal reflects the arrangement
  of the particles within the solid

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SOLIDS

• Unit cells put together make a crystal lattice
  (skeleton for the crystal)
• Crystals are classified into seven crystal
  systems cubic, tetragonal, orthorhombic,
  monoclinic, triclinic, hexagonal, rhombohedral
• Unit cell ? crystal lattice ? solid

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SOLIDS

• Amorphous Solid
• A solid with no defined shape (not a crystal)
• A solid that lacks an ordered internal structure
• Examples Clay, PlayDoh, Rubber, Glass, Plastic,
  Asphalt
• Allotropes
• Solids that appear in more than one form
• 2 or more different molecular forms of the same
  element in the same physical state (have
  different properties)
• Example Carbon
• Powder Graphite
• Pencil lead graphite
• Hard solid diamond

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SOLIDS
www.ohsu.edu/research/sbh/resultsimages/crystalvsg
lass.gif
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SOLIDS
Allotropes 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
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LIQUIDS

• Particles are spread apart
• Particles move slowly through a container
• No definite shape but do have a definite volume
• Flow from one container to another
• Viscosity resistance of a liquid to flowing
• Honey high viscosity
• Water low viscosity

chemed.chem.purdue.edu/.../graphics
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GASES

• Particles are very far apart
• Particles move very fast
• No definite shape and No definite volume

http//www.phy.cuhk.edu.hk/contextual/heat/tep/tra
ns/kinetic_theory.gif
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PLASMA

• Particles are extremely far apart
• Particles move extremely fast
• Only exists above 3000 degrees Celsius
• Basically, plasma is a hot gas
• When particles collide, they break apart into
  protons, neutrons, and electrons
• Occurs naturally on the sun and stars

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BOSE-EINSTEIN CONDENSATE

• Particles extremely close together
• Particles barely move
• Only found at extremely cold temperatures
• Basically Bose-Einstein is a cold solid
• Lowest energy of the 5 states/phases of matter

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GASES AND PRESSURE

• Gas pressure is the force exerted by a gas per
  unit surface area of an object
• Force and number of collisions
• When there are no particles present, no
  collisions no pressure vacuum
• Atmospheric Pressure is caused by a mixuture of
  gases (i.e. the air)
• Results from gravity holding air molecules
  downward in/on the Earths atmosphere
  atmospheric pressure decreases with altitude,
  increases with depth
• Barometers are devices used to measure
  atmospheric pressure (contains mercury)
• Standard Pressure is average normal pressure at
  sea level
• As you go ABOVE sea level, pressure is less
• As you go BELOW sea level, pressure is greater

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GASES AND PRESSURE

• Standard Pressure Values
• At sea level the pressure can be recorded as
• 14.7 psi (pounds per square inch)
• 29.9 inHg (inches of Mercury)
• 760 mmHg (millimeters of Mercury)
• 760 torr
• 1 atm (atmosphere)
• 101.325 kPa (kilopascals)
• All of these values are EQUAL to each other
• 29.9 inHg 101.325 kPa
• 760 torr 760 mmHg
• 1 atm 14.7 psi
• and so on.
• Say hello to Factor Label Method!!!!!!!!!!!!

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GASES AND PRESSURE

• STP
• Standard Temperature and Pressure
• Standard Pressure values are the values listed on
  the previous slides
• Standard Temperature is 0C or 273 K
• If temperature is given to you in Farenheit, must
  convert first!
• F (9/5)C 32
• C (5(F-32)) / 9 Remember order of
  operation rules
• K 273 C
• C K 273

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GASES AND PRESSURE

• Pressure Conversions
• Example 1 421 torr ? Atm
• Step 1 Write what you know
• Step 2 Draw the fence and place the given in
  the top left
• Step 3 Arrange what you know from step 1 such
  that the nondesired units canceling out so that
  you are only left with the units you want (i.e.
  atm)
• Step 4 Solve
• Step 5 Report final answer taking into account
  the appropriate significant figures

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GASES AND PRESSURE

• Pressure Conversions
• Example 2 32.0 psi ? torr

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TEMPERATURE

• Temperature is the measure of the average kinetic
  energy of the particles.
• 3 Units for Temperature
• Celsius
• Farenheit
• Kelvin
• Has an absolute zero
• Absolute lowest possible temperature
• All particles would completely stop moving
• Temperature Conversions
• Example 1 Convert 35C to F
• Example 2 Convert 300 Kelvin to C

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MEASURING PRESSURE

• Manometers
• Measure pressure
• 2 kinds open and closed
• Open Manometers
• Compare gas pressure to air pressure
• Example tire gauge
• Closed Manometer
• Directly measure the pressure (no comparison)
• Example barometer

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KINETIC ENERGY AND TEMPERATURE

• Energy of motion
• Energy of a moving object
• Matter is made of particles in motion
• Particles have kinetic energy
• KE (mv2)/2
• OR
• KE (ma)/2
• Kinetic Energy is measured in Joules
• 1 J 1kgm2/s2
• The mass must be in kg
• The velocity must be in m/s OR acceleration must
  be in m2/s2

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KINETIC ENERGY AND TEMPERATURE

• Calculate the KE of a car with a mass of 1500 kg
  and a speed of 50 m/s

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KINETIC ENERGY AND TEMPERATURE

• Calculate the KE of a car with a mass of 6780
  grams and a speed of 36 km/h

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KINETIC ENERGY AND TEMPERATURE

• Temperature-measure of the average kinetic energy
  of the particles
• Kelvin Scale
• Has an absolute zero (0K)
• Absolute lowest possible temperature
• In theory, all particles would completely stop
  moving
• Speed of Gases
• If two gases have the same temperature (particles
  moving at the same speed) how can you tell which
  gas has a greater speed?
• The only difference is mass!
• To find mass, use the periodic table

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KINETIC ENERGY AND TEMPERATURE

• Speed of Gases
• Example 1 If CH4 and NH3 are both at 284 K,
  which gas has a greater speed?
• Step One Add up the mass of each gas using the
  periodic table.
• Step Two The lighter gas moves faster (think
  about a race between a 100-pound man and a
  700-pound man, the lighter man would move faster)
• Example 2 Which gas has a faster speed between
  Br2 and CO2 if both are at 32F?

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TERMINOLOGY for PHASE CHANGES

• Melting-commonly used to indicate changing from
  solid to liquid
• Normal melting point-The temperature at which the
  vapor pressure of the solid and the vapor
  pressure of the liquid are equal
• Freezing-Changing from a liquid to a solid
• Melting and freezing occur at the same
  temperature
• Liquifaction-Turning a gas to a liquid
• Only happens in low temperature and high pressure
  situations

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TERMINOLOGY for PHASE CHANGES

• Difference in Gas and Vapor
• Gas-state of matter that exists at normal room
  temperature
• Vaport-produced by particles escaping from a
  state of matter that is normally liquid or solid
  at room temperature
• Boiling-used to indicate changing from a liquid
  to a gas/vapor
• Normal boiling point - temperature at which the
  vapor pressure of the liquid is equal to standard
  atmospheric pressure, which is 101.325 kPa
• Boiling point is a function of pressure.
• At lower pressures, the boiling point is lower

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TERMINOLOGY for PHASE CHANGES

• 2 types of boiling boiling and evaporation
• Evaporation takes place only at the surface of a
  liquid or solid while boiling takes place
  throughout the body of a liquid
• Particles have high kinetic energy
• Particles escape and become vapor
• Condensation-used to indicate changing from a
  vapor to a liquid

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TERMINOLOGY for PHASE CHANGES

• Sublimation - when a substance changes directly
  from a solid to a vapor
• The best known example is "dry ice", solid CO2
• Deposition-when a substance changes directly from
  a vapor to a solid (opposite of sublimation)
• Example-formation of frost
• Dynamic equilibrium - when a vapor is in
  equilibrium with its liquid as one molecule
  leaves the liquid to become a vapor, another
  molecule leaves the vapor to become a liquid. An
  equal number of molecules will be found moving in
  both directions
• Equilibrium - When there is no net change in a
  system

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TERMINOLOGY for PHASE CHANGES

• Points to Know
• Melting Point-Temperature when solid turns to a
  liquid
• Freezing Point-Temperature when liquid turns to a
  solid
• Boling Point-Temperature when a liquid turns to a
  vapor
• Doesnt boil unitl vapor pressure coming off
  liquid is equal to the air pressure around it
• Since air pressure changes with height, water
  does not always boil at 100C
• Condensing Point-Tempeature when vapor turns to
  liquid

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ENTROPY

• A measure of the disorder of a system
• Systems tend to go from a state of order (low
  entropy) to a state of maximum disorder (high
  entropy)
• Entropy of a gas is greater than that of a
  liquid entropy of a liquid is greater than that
  of a solid
• Solidslow entropy plasmahigh entropy
• Entropy tends to increase when temperature
  increases
• As substances change from one state to another,
  entropy may increase or decrease

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Le CHATELIERS PRINCIPLE

• Anytime stress is placed on a system, the sytem
  will readjust to accommodate that stress
• If a chemical system at equilibrium experiences a
  change in concentration, temperature, volume, or
  total pressure, then the equilibrium shifts to
  partially counteract the imposed change
• Can be used to predict the effect of a change in
  conditions on a chemical equilibrium
• Is used by chemists in order to manipulate the
  outcomes of reversible reactions, often to
  increase the yield of reactions

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Le CHATELIERS PRINCIPLE

• When liquids are heated (stress) they produce
  vapor particles (adjust)
• When liquids are cooled (stress) the particles
  inside tighten to form a solid (adjust)

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Le CHATELIERS PRINCIPLE

• Le Chateliers Principle explaining boiling and
  condensation using covered beaker partially
  filled with water
• At a given temperature the covered beaker
  constitutes a system in which the liquid water is
  in equilibrium with the water vapor that forms
  above the surface of the liquid.
• While some molecules of liquid are absorbing heat
  and evaporating to become vapor, an equal number
  of vapor molecules are giving up heat and
  condensing to become liquid.
• If stress is put on the system by raising the
  temperature, then according to Le Châtelier's
  principle the rate of evaporation will exceed the
  rate of condensation until a new equilibrium is
  established

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PHASE DIAGRAMS

• A diagram showing the conditions at which
  substance exists as a solid, liquid, or vapor
• Shows the temperature and pressure required for
  the 3 states of matter to exist
• Conditions of pressure and temperature at which
  two phases exist in equilibrium are indicated on
  a phase diagram by a line separating the phases
• Draw the phase diagram for water

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PHASE DIAGRAM-WATER
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PHASE DIAGRAM-WATER

• Explanation of Phase Diagram
• X axis-Temperature (C)
• Y axis- Pressure (kPa)
• Line AB line of sublimation
• Line BD boiling point line
• Line BC melting point line
• Point B triple point (all 3 states of matter
  exist at the same time)
• Tm melting point at standard pressure
• Tb boiling point at standard pressure

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HEAT in CHANGES of STATE

• Energy Diagrams (also referred to as Heating
  Curves)
• Graphically describes the enthalpy (the heat
  content of a system at sonstant pressure) changes
  that take place during phase changes
• X axis is Energy (Heat supplied)
• Y axis is Temperature

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HEAT in CHANGES of STATE

• Constructing Energy Diagrams
• Step 1 Determine/Identify the melting and
  boiling points for the specified substance
• Step 2 Draw x and y axis (energy vs temp)
• Step 3 Calculations
• First diagonal line Q mcDT
• First horizontal line Q mHf
• Second diagonal line Q mcDT
• Second horizontal line Q mHv
• Third horizontal line Q mcDT
• Add up all values!!!
• Draw the energy diagram for 10 grams of water as
  it goes from 25C to 140C