Skip to notes
wise otter.Chemistry
Contents
H1 Chemistry

Chemistry study notes

Reaction Kinetics

Infer a rate law from evidence and explain how concentration, temperature and catalysts change reaction speed.

A-Level 8873, revised syllabus (2026-2027)

Start learningQuick revisionRead whole chapter

Choose a topic

3 topics

  1. Measuring and modelling rate

    Use tangents, initial rates and concentration-time graphs.

  2. Why rates change

    Compare collisions, temperature and catalytic pathways.

  3. Enzymes

    Apply specificity and condition sensitivity.

Scope and references

Learning outcomes and sources

7. Reaction Kinetics (8873, 2026 revision; examinations 2026 and 2027). Use the outcome map to find the explanation for a particular syllabus requirement.

See the learning outcome map

  1. 7(a) Use kinetic vocabulary.

    • Rate, rate equation, order, rate constant, half-life, activation energy and catalysis.

    Rate measures change per timeChange one concentration at a time

  2. 7(b) Construct and use simple rate equations.

    • m,n = 0,1,2 for the stated H1 single-step cases.
    • (i) Initial-rate order deduction.
    • (ii) Zero/first-order concentration-time graphs.
    • (iii) Initial rate from concentration data; no integrated laws.

    Rate measures change per timeChange one concentration at a timeRecognise zero and first order from the whole curve

  3. 7(c) Explain constant first-order half-life.

    • Independence from starting concentration.

    Recognise zero and first order from the whole curve

  4. 7(d) Explain concentration effects.

    • Collision frequency at fixed temperature.

    Separate more collisions from a larger successful fraction

  5. 7(e) Explain activation energy using a distribution.

    • Boltzmann distribution and fraction above threshold.

    Separate more collisions from a larger successful fraction

  6. 7(f) Explain temperature effects on k and rate.

    • Both Boltzmann distribution and collision frequency.

    Separate more collisions from a larger successful fraction

  7. 7(g) Explain the catalytic effect.

    • (i) Alternative lower-Ea pathway and increased k.
    • (ii) Same-temperature Boltzmann interpretation.

    A catalyst changes the route, not the starting energy distribution

  8. 7(h) Explain heterogeneous catalytic action.

    • Adsorption/reaction/desorption; removal of nitrogen oxides from car exhaust.

    A catalyst changes the route, not the starting energy distribution

  9. 7(i) Explain enzyme properties.

    • Protein catalysts; substrate and reaction specificity; lock-and-key; temperature and pH sensitivity; link to 9(m), no named protein levels.

    An enzyme has a specific active site and suitable operating conditions