Frequently Examined
Reaction profiles are tested in almost every chemistry paper at GCSE. Common question types:
- Drawing a reaction profile โ must label axes, reactants, products, Ea, and ฮH
- Adding a catalyst curve โ same start/end, lower peak
- Reading Ea and ฮH from a diagram โ measuring the correct distances
- Explaining the effect of a catalyst โ lower Ea, more particles have enough energy
- Distinguishing Ea from ฮH โ very common source of confusion
Edexcel 1CH0: Examined in Paper 2 (1CH0/2). Drawing and interpreting energy profile diagrams, including the effect of a catalyst on activation energy, is a common Higher-tier question. In Edexcel-style questions, the command word "Suggest" appears frequently โ use your chemistry knowledge to apply to an unfamiliar context.
Quick Check: A catalyst is added to a reaction. What changes on the reaction profile and what stays the same?
What CHANGES: the activation energy (Ea) decreases โ the peak of the profile is lower. The curve takes a different, lower pathway. What STAYS THE SAME: the energy levels of the reactants and products remain the same, so the overall energy change (ฮH) is unchanged. The catalyst provides an alternative pathway but does not alter the energy stored in the reactants or products.
This exam focus covers Exam Focus within Reaction Profiles for GCSE Chemistry. Revise Reaction Profiles in Energy Changes for GCSE Chemistry with 28 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 11 of 13 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Practice questions for Reaction Profiles
What does activation energy represent on a reaction profile?
Explain how a catalyst affects the activation energy shown on a reaction profile. [2 marks]