Kinetic Theory of Matter (KTM)

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Kinetic Theory of Matter (KTM)

• AKA
• Kinetic Molecular Theory (KMT)
• Molecular Kinetic Theory (MKT)
• Not associated with TKMthe international postal
  code for Turkmenistan

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Rule 1

• All matter is composed of particles in constant
  motion

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Rule 2

• Temperature is a measure of the kinetic energy of
  the particles.

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Rule 2 (a and b)

• Temperature is a measure of the kinetic energy of
  the particles.
• a) When you heat a sample, the particles speed up
• b) When you cool a sample the particles slow down

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After that, things get hazy.

• ?

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Consider the state

• Solid Liquid Gas

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Particles in motion

• Solid Liquid Gas

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Particles in motion

• Solid Liquid Gas

Vibrating about a fixed position
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Particles in motion

• Solid Liquid Gas

Moving over and around other particles, unlikely
to escape surface
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Particles in motion

• Solid Liquid Gas

Moving freely, colliding with other particles and
the walls of container
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Consider state changes
Gas
Sublimation
Solid
Melting
Condensation
Freezing
Boiling, evaporation, vaporization
Liquid
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Particles on particles

• Solid Liquid Gas

Particles in contact
Particles not touching
Particles in contact
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This is huge. Really.
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Values and preferred units

• Patmospheres
• Tkelvins
• VLiters
• nmoles

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Conversions

• P 1 atm 760 mmHg760torr
• 101.3 kPa101,325 Pa
• T T(k) T(oC) 273
• V 1L1000 ml.001 m3

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How fast do particles move?

• It depends on

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How fast do particles move?

• It depends on
• Temperature
• Size of the particle

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How fast do particles move?

• It depends on
• Temperature High T ? faster motion
• Size of the particle Smaller ? faster

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Cool, medium, warm
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Phase diagrams
What about water?
P
1 atm
0 atm
T
0 k
273 k
373 k
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Phase diagrams
What about water?
Water melts / freezes
Water boils/ condenses
P
1 atm
0 atm
T
0 k
273 k
373 k
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Phase diagrams
What about water?
P
Water is a solid
Water is a liquid
Water is a gas
1 atm
0 atm
T
0 k
273 k
373 k
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Phase diagrams
What about water?
Increasing pressure will melt ice
Decreasing pressure will boil water
P
Water is a liquid
Water is a solid
Water is a gas
1 atm
0 atm
T
0 k
273 k
373 k
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Phase diagrams
What about water?
P
Water is a liquid
Water is a solid
Water is a gas
1 atm
Sublimation occurs at low T and P
0 atm
T
0 k
273 k
373 k
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Phase diagrams
What about water?
P
Water is a liquid
Water is a solid
Water is a gas
1 atm
0 atm
T
0 k
273 k
373 k
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Phase diagrams
Describe these processes
Water is a liquid
A
B
H
P
Water is a solid
I
C
G
1 atm
E
Water is a gas
D
F
0 atm
T
0 k
273 k
373 k
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Phase diagrams
Describe these processes
P
Heating curve lab
1 atm
Vacuum pump demo
0 atm
T
0 k
273 k
373 k
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Phase diagrams
Water
P
Normal melting point
1 atm
Normal boiling point
Triple point
0 atm
T
0 k
273 k
373 k
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Phase diagrams
Water
P
1 atm
Critical pressure
0 atm
T
0 k
273 k
373 k
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Phase diagrams
Most other substances
P
Critical pressure
Critical temperature
0 atm
T
0 k
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The phase diagram for water
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Phase diagrams
1 atm
P
0 atm
T
0 k
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Phase diagrams
1 atm
P
Critical pressure
Critical temperature
0 atm
T
0 k
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The phase diagram for CO2
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The phase diagram for water
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Can you explain why each of these phenomena
occurs?

• Thermal expansion of a solidsolids expand when
  heated
• Thermal expansion of a liquid liquids expand
  when heated
• Thermal expansion of a gas gasses expand when
  heated

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Can you explain why each of these phenomena
occurs?

• Compressibility of gassesgasses can be
  compressed into a smaller volume
• Incompressibility of liquids liquids cant be
  compressed into a smaller volume
• Incompressibility of solids solids cant be
  compressed into a smaller volume

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Can you explain why each of these phenomena
occurs?

• Conduction of heat between two objects in
  contactthe cool one warms up.
• Heat flow stops when temperatures are equal

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Can you explain why each of these phenomena
occurs?

• Fluidity of gassesgasses flow, they have no
  fixed shape
• Fluidity of liquidsliquids flow, they have no
  fixed shape
• Rigidity of solidssolids do not flow, they have
  a fixed shape

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Can you explain why each of these phenomena
occurs?

• Melting point of a solid at a certain
  temperature, a solid changes into a liquid
• Boiling point of a liquid at a certain
  temperature, a liquid changes into a gas
• Freezing point of liquids at a certain
  temperature, a liquid changes into a solid
• Melting is endothermic (requires heat)
• Boiling is endothermic (requires heat)

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Can you explain why each of these phenomena
occurs?

• Liquification of gasses is accomplished at low
  temperatures and high pressures
• Sublimation of solids (to gas) at low pressures
• Sublimation of solids (to gas) at high
  temperatures
• Evaporation cools a liquid
• You can see your breath on a cold day

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Can you explain why each of these phenomena
occurs?

• Boyles Law when the volume of a gas is reduced,
  its pressure increases
• Charles Law when gasses are cooled, their
  volumes act as if they will reach zero volume at
  a temperature of absolute zero
• Avogadros Law identical volumes of gasses
  contain the same number of particles
• Grahams law heavier gasses diffuse slower
• Daltons law of partial pressures the total
  pressure of a mixture of gasses is the sum of the
  pressures of each gas.

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Can you explain why each of these phenomena
occurs?

• Decrease in boiling point of a liquid with lower
  pressure
• Increase in boiling point when solutes are added
  to a solvent
• Decrease in freezing point when solutes are added
  to a solvent
• Metals conduct heat better than other solids