Chemguide: Support for CIE A level Chemistry
Learning outcomes 5.1.1 and 5.1.2
Enthalpy change, ΔH
These two statements are simply an introduction to enthalpy changes during reactions.
Before you go on, you should find and read the statements in your copy of the syllabus.
You should read the page introduction to chemical energetics in the Physical Chemistry section of Chemguide.
This statement is concerned with energy diagrams showing changes in energy during reactions. I tend to call these "energy profiles"; the syllabus uses the term "reaction pathway diagram".
You will these explained on the Chemguide page energy profiles.
The examples given on that page are simply that - examples. Although you will eventually have to know about these, there is no need to learn them at the moment.
All you need to know is that a reaction that takes place in a single step will have a different energy profile from one which takes place in two steps - and know what those two profiles look like.
© Jim Clark 2019