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8873 / 2027
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)

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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

Learning outcomes

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

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  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