GCSE Chemistry · Edexcel 1CH0 · Topic 7A
Rates of reaction
Key points
- Measure rate by collecting gas (gas syringe), measuring mass loss, or timing a cloudy precipitate to hide a cross. Mean rate = amount changed ÷ time.
- Collision theory: reactions happen when particles collide with enough energy (the activation energy).
- Higher temperature: particles move faster, collide more often and more collisions have enough energy.
- Higher concentration or pressure, or larger surface area (smaller pieces): more frequent collisions.
- Catalysts speed up reactions by giving an alternative route with a lower activation energy and are not used up. Enzymes are biological catalysts.
- Core practical: investigate the effect of temperature on sodium thiosulfate and acid, and of surface area or concentration on marble chips and acid.
- On a rate graph, a steeper gradient means a faster rate; draw a tangent to find the rate at a point (higher tier).
Topic notesPremium
The rate of a reaction is how quickly reactants are used up or products are formed. Chemists control rates every day, from speeding up industrial processes to slowing down food going off, and collision theory explains how they do it.
Unlock the full notes with Premium
Premium includes full topic notes, the paper generator, self-quizzes and progress tracking.
Practise this topicPremium
Premium members can generate an exam-style paper with a mark scheme, or take a quick quiz, on Rates of reaction.