11 Asa Chemistry Thermochemistry Lessonplan

Instructional Objectives

(a) explain that some chemical reactions are accompanied by energy changes, principally in the form of heat energy; the energy changes can be exothermic (∆H, negative) or endothermic
(b) explain and use the terms:
(i) enthalpy change of reactionand standard conditions, with particular reference to: formation, combustion, hydration, solution, neutralisation, atomisation
(ii) bond energy(∆Hpositive, i.e. bond breaking)
(iii) lattice energy (∆H negative, i.e. gaseous ions to solid lattice)
(c) calculate enthalpy changes from appropriate experimental results, including the use of the relationship enthalpy change, ∆H= –mc∆T
(d) explain, in qualitative terms, the effect of ionic charge and of ionic radius on the numerical magnitude of a lattice energy
(e) apply Hess’ Law to construct simple energy cycles, and carry out calculations involving such cycles and relevant energy terms, with particular reference to:
(i) determining enthalpy changes thatcannot be found by direct experiment, e.g. an enthalpy change of formation from enthalpy changes of combustion
(ii) average bond energies
(iii) the formation of a simple ionic solid and of its aqueous solution
(iv) Born-Haber cycles (including ionisation energy and electron affinity)
(f) construct and interpret a reaction pathway diagram, in terms of the enthalpy change of the reaction and of the activation energy

Teaching process

  • Involves problem solving of enthalphy cahnges and Hess' law
  • Practice with energy profile diagrams

Suggested Reading

Activity

  • Experiments with Calorimetry
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