Rate of reaction: GCSE Chemistry
Collision theory, factors affecting rate, catalysts, rate graphs, reversible reactions and equilibrium
The short version
Collision theory: successful collisions need enough energy (activation energy) and the right orientation. Graphs of product vs time get shallower as reactants are used up.
Key idea
Write both: frequency of collisions AND energy of collisions
Grade 2–3: If bits bump more, the reaction goes faster. Time how much gas you get.
Grade 5–6: I can write the mean rate equation and name mass loss, syringe, or disappearing cross.
Grade 9: I always mention orientation as well as energy. I never mix up time-to-finish with rate: shorter time means higher rate.
Go a bit deeper
Temperature: more collisions AND more with energy greater than Ea
Grade 2–3: Crush it, heat it, or make the acid stronger and it fizzes faster.
Grade 5–6: I can write a collision-frequency sentence for concentration, pressure and surface area.
Grade 9: Temperature mark scheme gold: more frequent collisions AND more particles have energy greater than the activation energy. Fair test: same mass and same surface area unless SA is the variable.
Worked example
Worked example
Grade 2–3: If bits bump more, the reaction goes faster. Time how much gas you get. Grade 5–6: I can write the mean rate equation and name mass loss, syringe, or disappearing cross. Grade 9: I always mention orientation as well as energy. I never mix up time-to-finish with rate: shorter time means higher rate.
Lessons in this topic
- Collision theory
- Factors affecting rate
- Catalysts
- Rate graphs
- Reversible reactions
- Equilibrium (Higher)
In the app each lesson is video (when we have a real YouTube id) then intro, learn and summary steps.
What the examiner wants
Mean rate = quantity of reactant used or product formed ÷ time. Higher: Le Chatelier predicts how concentration, pressure and temperature shift equilibrium position.
Try these questions
Cover the answers and have a go first. Worked solutions are underneath.
A successful collision needs
Mean rate can be calculated as
Increasing concentration increases rate because
Powdered marble reacts faster than chips of the same mass because of
Common mistakes
- Do not mix up time for the reaction to finish with rate. A shorter time means a higher rate.
- Pressure only matters for gases. Heating a solution is temperature, not pressure.
- A catalyst does not give particles extra energy, does not increase temperature by magic, and does not change yield. It lowers the energy barrier.
- Do not plot time on the y-axis and call it rate. Rate goes up when time goes down.
Answers and working
Frequently asked questions
Is GCSE Rate of reaction on Combined Science and Triple?
Rate of reaction is on Combined Science and on Triple Chemistry. Progress is shared in the ReviseEasy app.
Which exam board is this Rate of reaction page for?
The ideas are board-agnostic for AQA, Edexcel, OCR, WJEC and CCEA. Paper lengths and question numbers differ — check your specification.
Is Rate of reaction Foundation or Higher?
The core ideas appear on both tiers. Higher papers add extra application and some HT-only detail, marked in lessons with a Higher badge.
Learn, try, get feedback, fix the mistake
Open the stepped lesson, then the quiz with hints. Required-practical and calculation questions use the same method you will need in the paper.
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