AP CHAPTER 6 OUTLINE
ENEGY AND THERMOCHEMISTRY

I. Kinetic and Potential energy Revisited
     A. Kinetic and Potential Energy
          1.
Kinetic Enegy (KE) -- energy of motion associated with mechanical work
               a. KE = 1/2mv
2
          2.
Potential energy (PE) -- stored energy based on repulsive and attractive forces of objects
               a. PE can change into KE and vice versa
          3. Increase PE by...
               a. objects that are attracted to each other are pulled apart
               b. objects that are repulsive to each other are pushed together
          4. Law of Conservation of Energy
               a. Energy = a constant in the universe
     B. Units of Energy
          1.
Joule (J) -- SI unit of energy
               a. KE in 2 kg object moving 1 m/s
               b. kilojoule (kJ)
          2.
calorie (cal) -- energy needed to raise the temperature of 1 g of water by 1 degree Celsius
               a. 1 cal = 4.184 J (1 kcal = 4.184 kJ)
     C. Chemical Bonds and Chemical Energy
          1.
Chemical bond -- net attractive force must be at work in compounds to bind their atomic nuclei and electrons together
          2.
Chemical energy -- PE that resides in chemical bonds that can be changed to KE
II. Kinetic Theory of Matter
     A. Kinetic Energy Distribution in a Sample of Matter
          1.
Kinetic theory of matter -- atoms and molecules are in constant motion
               a.
Molecular kinetic energy -- energy associated with molecular motion
               b.
Temperature -- measure of average kinetic energy of its atoms and molecules
                    1. Kelvin temperature is directly proportional to the average molecular KE
          2. Temperature Changes and What They Tell Us
               a.
a change in temperature, is a change in average molecular KE
               b.
a change in temperature, is a change in total KE of object
          3. Kinetic Theory and Liquids and Solids
               a. Liquid molecules have random motion
               b. Solid molecules have random motion
          4. Gas, liquid, and solid at same temperature, the molecules in each phase have same average KE
               a. PE are different
     B. Kinetic Theory and the Transfer of Heat
          1. Transfer of Heat -- A Molecular Explanation
               a. Heated molecules move faster, collide with other molecules and transfer energy

III. Energy Changes in Chemical Reactions
     A. The Energy Consequences of Bond Making and Breaking
          1. Bond forming decrease potential energy
          2. Bond breaking increase potential energy
     B.
Exothermic reaction -- reaction in which heat is produced
          1. products have less potential energy then the reactants
     C.
Endothermic reaction -- reaction in which heat is absorbed
          2. products have more potential energy then the reactants
IV. First Law of Thermodynamics: Heat and Work
     A.
Thermodynamics -- study of heat flow
          1.
System -- part of universe we are studying
          2.
Surroundings -- everything else in the universe besides the system
          3.
Boundary -- separates the system and surroundings
          4.
Insulated system -- no energy crosses the boundary
          5.
Open system -- open to the atmosphere
          6.
Closed system -- not open to the atmosphere
          7.
Adiabatic change -- no heat flow between the system and surroundings
          8. Exothermic reaction --
system becomes warmer and net decrease of PE. If uninsulated the system gives off heat to surrounding
          9. Endothermic reaction --
system becomes cooler and net increase in PE.  If unisulated the system receives heat from the surroundings
        10. Isothermic change -- heat exchanges allow the system to maintain a constant temperature
                a. HEat flows spontaneously from regions of high temperatures to regions of low temperatures
     B. State Functions and the State of a System
          1.
State function -- any property that does not depend on a system's history or future
          2.
State of a system -- the chemical composition plus its pressure, temperature, and volume
               a. Independent from the method/mechanism by which a change occurs
     C.
Internal Energy -- total energy of a system (E or Esystem)
          1. E
system =  (KE)system +  (PE)system
          2. Reactions
               a. Delta E  = E
final -  Einitial          or          Delta E  =  Eproducts -  Ereactants
     D. Heat and Work
          1.
Work -- exchange of energy when a pushing force moves something through a distance
          2.
First Law of Thermodynamics -- Delta E  =  q  +  w
               a. q = heat, w = work

               b. q  is positive -- heat is absorbed by system
               c. q is negative -- heat is released by system
               d. w is positive --work is done on system
               e. w is negative -- work is done by system
   
E. Heat, Work, and State Functions
          1. Delta E can be entirely in the form of heat or can be a combination of heat and work
               a. Delta E is a state function (same fro every path of energy change for one system), but q and w are not state functions (depend upon the path they are taking)
     F. Work Related to Gas Expansion or Compression
          1.
Pressure -- force acting on a unit of area (P = force/area)
          2.
Atmospheric pressure -- pressure exerted by Earth's air simply by virtue of its weight
               a.
Standard atmosphere of pressure (atm) = 14.7 lbs/in.2
          3. Pressure-Volume Work
               a. Changes of P and V with a pressurized gas cause work on the surroundings
     G. Heats of Reaction at Constant Volume
          1.
Heat of Reaction -- amount of heat absorbed or released in a chemical reaction
          2.
Calorimeter -- apparatus used to measure changes in chemical reactions
          3.
Heat of reaction of constant volume (qv) = Delta E
     H.
Enthalpy (H) -- Heat content of a system at constant pressure
          1. H = E + PV
          2. H is a state function
          3.
Enthalpy change (DeltaH) -- Delta H = Hfinal - Hinitial
               a. Also a state function
              
b. Delta H positive in endothermic reactions
               c. Delta H negative in exothermic reactions

     I. Enthalpy Changes and Heats of Reaction at Constant Pressure
          1. V change, Constant P, then Delta H = Delta E + P Delta V
          2.
Heat of reaction at constant pressure (qp) = Delta H
     J. The Difference between Delta E and Delta H
          1. Differences between Delta E and Delta H are very small
               a. Difference is P-V work done by system when no pressure change
              
b. Increase in volume, Delta H is less negative than Delta E
               c. Decrease in volume, Delta H is more negative than Delta E

          2. Delta E = Delta H for reactions having no change in volume
V. Measuring Energy Changes: Calorimetry
     A.
The Special Place of Heat as a Form of Energy
          1.
All forms of energy can be transformed into  heat
               a. Quantity of any energy can be determined by letting heat flow into cooler water during an exothermic process
               b.
Thermal property -- describe a system's ability to absorb or release heat without a chemical change
                    1.
Specific heat, heat capacity, molar heat capacity
     B.
Specific Heat -- quantity of heat needed to raise the temperature of 1 gram of a substance 1degree C
          1.
Calorie -- heat needed to raise the temperature of water 1 degree C
               a. Specific heat of water = 1 cal/gOC = 4.18J/g
oC
     C.
Heat Capacity -- product of the specific heat and mass (ability of an object to absorb or release heat)
          1. Units = J/
oC
          2. Specific heat - intensive property (thermal property that is unique to each substance)
          3. Heat capacity - extensive property (thermal property that depends on the size of the sample)
     D.
Molar Heat Capacity -- heat needed to raise the temperature of one mole of a substance one degree C
          1. Units = J/moloC
     E. The Unusual Thermal Properties of Water
          1. High specific heat capacity -- large amounts of energy to change temperature of water
     F.
Calorimetry -- Science of using a calorimeter for determining heats of reaction
          1. Coffee Cup Calorimeter -- Solution Calorimeter
VI. Enthalpy Changes in Chemical Reactions
     A. Standard Conditions for Enthalpy Changes
          1. Temperature = 25
oC
          2. Pressure = 1 atm (14.7 lbs/in.
2)
     B.
Standard Heats of Reaction -- Delta H for a reaction occurring under standard conditions and involving the actual nuber of moles specified by the balanced equation
          1. Delta H
o used to represent standard heat of reaction
               a.
Thermochemical equations -- includes the standard heat of reaction (neg. = exo, pos. = endo)
                    1. Must include states of matter
                    2. Delta H
o is only true when the coeeficients of reactants and products are present
                    3. Delta H
o follows mole fractions like all other substances
VII. Combining Thermochemical Equations: Hess's Law
     A. Multiple versus Single Path Routes and Enthalpy Changes
          1.
The enthalpy changes of a multiple path reaction  will equal the enthalpy change of a single path reaction if the original reactants and products are exactly the same
     B.
Enthalpy Diagrams
          1. Horizontal lines -- absolute values of enthalpy (higher line = higher enthalpy)
          2. vertical arrows -- enthalpy changes
         
3. Exothermic reaction -- reactants have a higher line than products
          4. Endothermic reaction -- reactants have a lower line than products

Example:









     C. Hess's Law
          1.
Hess's Law of heat summation -- the value of Delta Ho for any reaction that can be written in steps equals the sum of the values of Delta Ho of each of the individual steps
               a. Rules for Manipulating Thermochemical Equations
                    1. when an equation is reversed, the Delta H
o changes sign
                    2. Formulas that cancel from both sides of equation must be in the same state
                    3. If cofficients are multiplied/divided by a factor, than the Delta H
o is multiplied/divided by the same factor
VIII. Standard Heats of Formation and Hess's Law
     A.
Standard enthalpy of formation (DeltaHof) [standard heat of formation] -- amount of heat absorbed or released whenone mole of a substance forms at 25oC and 1 atm of pressure in their standard state
          1. Table on pg. 260
          2.
DeltaHo =  (Delta Hof of products)  -  (Delta Hof of reactants)


Outline based upon:
     Brady, J. E., Holum, J. R., Russell, J. W. (2000).
Chemistry: The Study of Matter and Its Changes. (3rd ed.). New York: John Wiley & Sons, Inc. pp. 231-264.

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