Student will learn:

1
Thermal chemistry is study of the transfer of
heat in chemical reactions and physical changes.

• Student will learn
• 1. to read Phase diagrams
• 2. math calculations of energy for melting,
  freezing, vaporization, condensing or
  raising temperature of a compound or
  element.

2
Thermal Chemistry

• Phase any part of a system that has
• uniform composition and properties. (
  solid, liquid, gas)
• Fluid gas or liquid a substance that can flow
  and
• take shape of the container.
• Diffuse ability to mix with other liquids or
  gases (p.364 food coloring, perfume)

Overhead
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• Vaporization process - liquid or solid changes
  into a gas.
• you have added energy and vaporized it
• Evaporization process - particles escape from
  the surface of a non boiling liquid and become
  gas. naturally evaporated
• Volatile liquids liquids that evaporate readily
  finger nail polish remover
• Condensation process which a gas becomes a
  liquid
• rain, water drops on out side of glass of
  cold drink
• Boiling conversion of a liquid to a gas
• within the liquid as well as the surface.
• Boiling Point Temperature which vapor pressure
  of the liquid equals the atmospheric
  pressure.

4

• Freezing or solidification physical change of
  liquid to a solid by removal of heat or
  energy
• Freezing Point Temperature which liquid and
  solid have same average kinetic energy.
• Melting physical change of a solid to a liquid
• by the addition of energy.
• Melting point the temperature at which a
• solid becomes a liquid.
• Sublimation change of a solid directly to a
  gas.
• CO2.. Dry ice, Iodine, frost free freezer
• Deposition change of a gas directly to a solid.
  
• frost on grass or car windshield

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Phase Diagramsgraph which shows conditions of
phase changes
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• Triple point solid, liquid, gas coexist at
  equilibrium.

7

• Critical Temperature point
• cannot exist as a liquid regardless of
  pressure.
• The critical temperature point of water is
  373.99oc. Above this temperature, water cannot
  be liquefied, no matter how much pressure is
  applied.

8

• Critical Pressure point lowest pressure at
  which the substance can exist as liquid _at_
  critical temp.
• The lowest pressure at which water can exist as a
  liquid is 217.75 atm _at_ the critical temperature
  point.

9
Phase Diagram
Describe all phase changes that would occur when
heating the chemical from -80o to 20o at a
constant pressure of 10atm.
At room temperature what is the phase of this
chemical?
10
Phase Diagram
What are the phase changes at 16atm from -100o to
40o and their corresponding temperatures?
At room temperature what is the phase of this
chemical?
11
Phase Diagram
Given a sample of this chemical, how would you
phase change the liquid into a gas without
changing the temperature?
Where is the triple point? Where is the
critical point?
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Thermal Chemistry study of transfer of heat in
chemical reactions and physical changes.

• What is the difference?
• Temperature
• Heat
• Thermal energy

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• Temperature measurement of motion
• measurement of kinetic energy of
  the molecules . Wood
• . cold (vs) hot water
• . Fever of 105
• Normally use a thermometer

Heat The transfer of thermal energy. The
energy that flows from higher Temperature to
lower temperature. standing beside the
burning wood and feeling the warmth
Thermal energy total energy of matter
measured in joules Q thermal energy
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• Heat of Fusion energy required to melt solid to
  a liquid
• Q m Hf Q energy M mass Hf heat
  of fusion
• Heat of Vaporization energy required to
  vaporize a liquid
• Q m Hv Q energy m mass Hv heat
  of vapor
• look on your chemistry tables
• Specific Heat amount of energy required to
  raise 1gram of substance 1 degree of
  temperature.
• Q m Cp t
• look on your chemistry tables

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• Calculate the amount of energy required to melt a
  small ice cube weighing 24 grams.
• 2. Calculate the amount of energy required to
  produce steam from 100 mL of water.

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• 3. Find the molar heat of vaporization for a
  substance, given that 4.22 mol of the substance
  absorbs 32.8 kJ of energy when it changes from a
  liquid to a gas.
• 4. Aluminum is used in manufacturing Pepsi-cola
  cans. How much heat energy does the factory need
  to provide to melt the 3 grams of aluminum needed
  per can? The factory produces 3,000 cans per
  hour. How much energy is needed per hour?
  Aluminums melting point is 660 degrees Celsius.

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• Specific Heat amount of energy required to
  raise 1gram of substance by 1 degree
• Q m Cp t
• Looking at the chart of specific heat.
• Which requires the most heat to heat up?
• iron pipe or lead pipe
• Which requires least amount of heat to heat
  up?
• magnesium or gold
• Which requires least amount of heat
  to heat up?
• Fe, Zn, Ti

20

• How much heat is needed to raise the temperature
  of a 20g aluminum Pepsi-cola can 35 degrees?
• Calculate the heat lost from a 5g copper penny if
  cooled from 25oc to 3oc in the freezer.

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1. Calculate the mass of water that uses 2508J of
   energy in raising its temperature from 80oC to
   100oC.
2. Calculate the temperature rise if 224.25J of heat
   energy was added to a 30gram ice cube.

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• HEATING CURVES
• VS
• COOLING CURVES
• HANDOUT CURVE SHEET

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label
Heating-Cooling curve ( Enthalpy of Fusion and
Vaporization
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Theory pt.1 The quantity of heat absorbed to
melt a solid the quantity of heat released to
solidify the liquid.
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Theory pt.2 The quantity of heat absorbed to
vaporize a liquid the quantity of heat released
to condensate the vapor.
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Theory pt.3 All solids absorb heat as they melt
. This causes a phase change rather than a
temperature change.
Ex) ice melting Temperature remains constant
until all ice has melted.. The temperature of
water will increase only after all ice has
melted. Ex) boiling water.
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Which segments on the curve represent constant
temperature? What is the boiling point of this
substance? How much energy is needed for
vaporization? If this chart is based on 2 grams
of substance how much energy is needed to melt 10
grams of the substance.
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At what temperatures does phase changes
occur? Which portion represents an decrease in
heat absorbed and potential energy decreases
while Kinetic energy remains constant? How much
is the Heat of Vaporization? At what
temperature is condensation?
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What is the melting Temperature? How many
minutes does this take to melt? What is the
boiling point?
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• Stop

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Equilibrium

• Equilibrium two opposing changes occur at equal
  rates
• Closed system Matter can not enter or leave.
• but energy can example sunlight, heat
  from a burner, cooling by ice.
• Equilibrium equations
• Whenever a liquid changes into a vapor it
  absorbs heat energy.
• liquid heat energy vapor
• Whenever a vapor condenses, it gives off heat
  energy
• vapor liquid heat energy
• Whenever a liquid , vapor reaches equilibrium
• liquid heat energy vapor

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• Le Chateliers principle When a system is at
  equilibrium and is disturbed by a stress it
  attains a new equilibrium that minimizes the
  stress.
• Stress is typically temperature, concentration,
  pressure.
• Need to know 2nd Law of Thermodynamics
• Heat always travel from higher temp to lower
  temp.
• same with energy, voltage, concentration,
  pressure, etc..everything
• endothermic absorbing energy or heat
• exothermic releasing energy or heat

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• liquid heat vapor
• Equilibrium and temperature p.374
• Add extra heat.shift toward vapor .
  endothermic reaction
• Subtract heat (cool with ice) shift toward
  liquid .. exothermic reaction
• Equilibrium and Concentration p.375
• Add extra liquid .. Shift toward vapor
• Add extra vapor . Shift toward liquid
• Equilibrium and Pressure p.376
• Pressure exerted by a vapor with its
  corresponding liquid
• is called equilibrium vapor pressure
• Add heat increase vapor
• which increases pressure vapor onto liquid.
• Subtract heatdecrease vapor
• which decreases pressure of vapor onto
  liquid.
• think of your pepsi-cola drinks easier to
  keep carbonated when cold