GCSE Chemistry: Rates of Reaction
Rates of reaction is the most practical-flavoured topic in GCSE Chemistry — nearly every question is anchored in an experiment someone could actually run — and it rewards one skill above all: explaining every observation through collision theory. This quiz builds exactly that habit.
The measurement questions use the three standard experimental setups: collecting hydrogen gas from magnesium and acid (60 cm³ in 40 seconds giving a mean rate of 1.5 cm³/s), tracking mass loss as carbon dioxide escapes a flask (4.2 g over two minutes — with the minutes-to-seconds conversion that catches the unwary), and the cloudiness methods for precipitate-forming reactions. A rearrangement question runs the rate formula backwards, finding the time from a volume and a rate.
The factors questions cover concentration, temperature, surface area and catalysts — first as predictions, then as explanations. Collision theory carries the explanatory weight throughout: concentration increasing collision frequency, grinding a solid exposing more surface for collisions, and the crucial two-part temperature explanation (more frequent collisions AND a greater proportion of particles exceeding the activation energy) that distinguishes full-mark answers.
Catalysts get precise treatment: they provide an alternative pathway with lower activation energy, they emerge unchanged, and — the misconception the quiz explicitly targets — they do not increase the yield of product, only the speed of reaching it.
Every calculation carries its units through the working, and every explanation ends at the particle level, mirroring the "explain in terms of particles" phrasing that GCSE mark schemes use for this topic.
- Calculate mean rates from gas volume, mass loss or time data with correct units
- Choose appropriate methods for measuring the rate of a given reaction
- Explain concentration and surface area effects through collision frequency
- Give the two-part collision theory explanation for temperature effects
- State precisely what catalysts do and do not change
Topic scope follows the Department for Education's GCSE chemistry subject content (shared in part with combined science), rate and extent of chemical change strand: measuring and calculating rates, factors affecting rate, collision theory and catalysts.
Sample question
How does a catalyst affect the energy profile of a chemical reaction?
- It increases the total energy of the products
- It provides an alternative reaction pathway with a lower activation energy
- It increases the frequency of collisions by heating the mixture
- It decreases the total energy of the reactants
See the answer
It provides an alternative reaction pathway with a lower activation energy
A catalyst works by providing an alternative pathway for the reaction that requires less activation energy, allowing more particles to have sufficient energy to react upon collision.
Try this quiz →Try this exam →Practice these flashcards →Try this written work →
- GCSE Chemistry: Tests for Ions and Flame Emission Spectroscopy
- GCSE Chemistry Practicals: Making Salts and Purifying Water
- GCSE Chemistry Practicals: Rates, Temperature Changes and Electrolysis
- GCSE Chemistry: Nanoparticles, Transition Metals and Ionic Equations
- GCSE Chemistry: Moles in Solution, Titrations and Yield
- GCSE Chemistry: Haber Process, Fertilisers and Materials
- English Language
- English Literature
- History
- Geography
- Biology
- Mathematics
- Physics
- Computer Science
- Business
- Religious Studies
- French
- Spanish
GCSEs are awarded by AQA, Pearson Edexcel, OCR, WJEC/Eduqas and CCEA, and regulated by Ofqual, Qualifications Wales and CCEA Regulation, the regulators for England, Wales and Northern Ireland. Zestly is not affiliated with or endorsed by Ofqual or any awarding body. These materials are our own and reproduce no past-paper content.