Download AP Chemistry Objectives Chpt 6 Thermo

AP Chemistry Objectives Chpt 6 Thermo
1. Define energy, law of conservation of energy, potential energy, kinetic energy, Joule,
heat, work, pathway, state function, system, surroundings, endothermic, exothermic,
thermodynamics, and first law of thermodynamics.
Energy – the ability to do work or produce heat. (units Joules,
calories, Btu)
Kinetic energy – energy of motion. KE = 1/2mv2 .
Potential energy – energy of position, stored energy, or composition.
Law of conservation of energy – sum of energy in universe remains
constant. Energy can not be crated or destroyed, but can be changed from
one form to another.
Joule – unit of energy of energy or work (Newton – meter).
Heat – random motion of particles in a substance. Involves transfer of
heat.
Work – force applied over a distance- must be movement.
Pathway – specific conditions in which energy transfer is divided.
State function – a property that depends only on its present conditions,
does not depend on its past or future. (Example altitude on a mtn depends
ONLY on the distance between the bottom and top, NOT the path taken to
get to the top.
State property – same as above.
System – focus of attention
Surroundings – everything in the universe excluding the system.
Exothermic – energy flows out of the system. Releases heat to the
surroundings. Q is negative. Products have lower PE than reactants.
Endothermic –energy flows into the system. Absorbs heat. In chemical
rxn the products have higher PE than reactants. Q is positive.
2. Discuss the energy flow between a system and its surroundings.
3. Discuss pathways and state functions in a paragraph and with a drawing.
4. Discuss endothermic and exothermic rxns from the point of the system.
5. State the first law of thermodynamics.
Conservation of energy. Energy in universe is constant.
6. Discuss changes in a system’s internal energy
E, q, from the systems point of view.
7. Calculate the work that results from changes in the volume of a gas at constant
pressure.
q + w
Note work is done is done on (or by the system by changes in volume)
Work = -pv
v = vf – vi
8. Define enthalpy, calorimeter, calorimetry, heat capacity, specific heat capacity,
constant pressure calorimetry, constant volume calorimetry.
Enthalpy, H – is the sum of the internal energy and the pressure volume product of
the system. It is a state function.
Defined as H = E + PV
Heat capacity – amount of heat/energy needed to change the temp of a
substance one degree.
Specific heat capacity – amount of heat needed to change the temp of one
gram of substance one degree.
9. Discuss the meaning of enthalpy and changes in enthalpy.
Change in enthalpy - PV
= qp
products – H reactants
10. Calculate changes in enthalpy.
11. Discuss how changes in enthalpy are measured.
12. State Hess’s Law.
If a reaction occurs in steps (even theoretically), the enthalpy change for the overall
(net) process is the sum of the enthalpy changes for the individual changes.
13. Calculate delta H from a chemical rxn.
1. If reaction is reversed the sign for H is reversed.
2. The magnitude if H is proportional to the amount of reactants involved. If coef
in equation is multiplied the value of is multiplied.
14. Discuss standard enthalpies of formation.
Definition - Ho , is the enthalpy change that occurs in the formation of 1 mol of
substance in its std state from the reference forms of the elements in their std state.
Std state of substance in soln is 1.00—M
Std state of solid or liquid is the pure element or compound at 1.0 atm
15. Use standard enthalpies of formation to calculate delta H.