Enthalpy changes are the result of heat transfers during chemical reactions.
We are familiar with the idea of exothermic and endothermic reactions from GCSE. Here, I start with clarifying the key language before moving on to look at determining enthalpy changes experimentally as well as theoretically, sharing foolproof methods for drawing out enthalpy cycles and using them to calculate an enthalpy change indirectly.
There is a tendency when teaching thermochemistry (the chemistry of energy changes) to leap straight in and assume that the basics covered at GCSE are still fresh in everyone’s mind, and that students have a genuine understanding of the chemistry behind exothermic and endothermic reactions simply because they can sort of sketch an energy level diagram.
In my experience, teachers, let alone students, struggle to explain how heat transfers in reactions can be used for useful work . . . so don’t skip the first post which is written specifically to get you up to speed and iron out any misconceptions.
Thermochemistry – the foundations, the terminology and the misconceptions!
Enthalpy change of combustion – using experimental data in calculations
Enthalpy change of neutralisation – using experimental data in calculations
Using Hess’s law to draw all the different enthalpy cycles for calculating an enthalpy change
Using bond enthalpies to calculate an enthalpy change of reaction
Exam question practice!
Written to stretch and challenge your understanding and analysis skills, with A* perfect answers, exam tips and tricks 😍