Module 4: Drivers of Reactions Notes

Sections

1. 4A Exothermic and endothermic reactions Mastered

   System and surroundings, enthalpy and the sign of ΔH, exothermic and endothermic reactions and physical changes, thermochemical equations, and the practical investigation of temperature changes in combustion and in dissolving ionic substances.

   Open notes
2. 4B Calorimetry and heat of solution Mastered

   Specific heat capacity, q = mcΔT, molar enthalpy change, the coffee-cup calorimeter, measuring heats of solution, cooling corrections by extrapolation, and analysing errors against secondary-sourced data.

   Open notes
3. 4C Heat of combustion Mastered

   Molar heat of combustion, measuring it with a spirit burner and with a bomb calorimeter, calibrating a calorimeter, heat of combustion per gram, and comparing fuels and foods.

   Open notes
4. 4D Energy profiles and catalysts Mastered

   Activation energy and the transition state, constructing and reading energy profile diagrams for exothermic and endothermic reactions, forward and reverse activation energies, and how catalysts provide an alternative pathway.

   Open notes
5. 4E Bond energies and enthalpy Mastered

   Explaining enthalpy changes as bond breaking and bond forming, the law of conservation of energy, average bond energies, estimating ΔH from bond energies, and why estimates differ from measured values.

   Open notes
6. 4F Hess's law Mastered

   Hess's law as a consequence of conservation of energy, the stepped reaction of carbon to carbon dioxide via carbon monoxide, rules for manipulating thermochemical equations, solving Hess's law problems, and the heat of formation of magnesium oxide investigation.

   Open notes
7. 4G Enthalpies of formation, photosynthesis and respiration Mastered

   Standard states and standard enthalpy changes, standard enthalpy of formation, calculating ΔH° from enthalpies of formation, finding enthalpies of formation from heats of combustion, and the enthalpy changes of photosynthesis and cellular respiration.

   Open notes
8. 4H Entropy Mastered

   The two drivers of change, entropy as the number of ways particles and energy can be arranged, modelling entropy changes, predicting the sign of ΔS from states and moles of gas, standard molar entropies and calculating ΔS°, and how entropy differs from enthalpy.

   Open notes
9. 4I Gibbs free energy and spontaneity Mastered

   Spontaneous and non-spontaneous reactions, combining enthalpy and entropy in ΔG° = ΔH° − TΔS°, the four combinations of ΔH and ΔS, calculating ΔG° from standard data, the effect of temperature on spontaneity, and the crossover temperature.

   Open notes
10. 4J Drivers of reactions review Mastered

    Summary of Module 4: energy changes, calorimetry, energy profiles, bond energies, Hess's law, enthalpies of formation, entropy and Gibbs free energy, with key formulas and a mixed HSC-style test.

    Open notes