Topic 8
Energetics I
Topic 8 introduces the heat energy changes that accompany chemical reactions. It covers exothermic and endothermic reactions, enthalpy level diagrams and reaction profiles, standard conditions and the standard enthalpy change definitions, measuring enthalpy changes by calorimetry, Hess’s law and enthalpy cycles, and mean bond enthalpies. The practical side is assessed in Core Practical 8.
Revision Notes
Changes
Enthalpy Changes and Standard Conditions
Exothermic and endothermic reactions, enthalpy level diagrams, activation energy and standard conditions.
Start revisingEnthalpies
Standard Enthalpy Changes
The standard enthalpy change definitions and the equation each one refers to.
Start revisingCalorimetry: Measuring Enthalpy Changes
Calculating ΔH from a temperature change, cooling curve corrections, errors and assumptions.
Start revisingLaw
Hess’s Law and Enthalpy Cycles
Building enthalpy cycles and calculating ΔH from formation and combustion data.
Start revisingEnthalpies
Bond Enthalpies
Mean bond enthalpy, calculating ΔH from bonds broken and made, and why the answers differ from Hess values.
Start revisingTopic 8 Energetics I – Edexcel A Level Chemistry
The following specification points outline the knowledge and skills students are expected to demonstrate for Topic 8. Energetics I is extended in Topic 13 Energetics II.
Enthalpy Changes and Standard Conditions
Standard Enthalpy Changes
Measuring Enthalpy Changes
Hess’s Law
Bond Enthalpies
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