Temperature & Reaction Rate
15 Questions · Sections A, B, C · Hidden Mark Schemes
The activation energy (Ea) threshold — the heart of this entire topic.
Why is food kept in a refrigerator?
[2 marks]A nurse stores medicine in a cool, dark cupboard. Explain why temperature affects the rate at which the medicine decomposes.
[2 marks]A chef boils pasta faster by turning up the heat. Using collision theory, explain why increasing the temperature of the water speeds up the cooking process.
[2 marks]An industrial chemist cools a reaction mixture to slow down an unwanted side reaction. What effect does cooling have on the rate of that reaction? Give TWO reasons.
[2 marks]Explain why milk stored at room temperature (25 °C) turns sour more quickly than milk stored in a fridge (4 °C).
[2 marks]Explain, using collision theory, why an increase in temperature increases the rate of a chemical reaction. [4]
[4 marks]The reaction between sodium thiosulfate and hydrochloric acid is carried out at 20 °C and again at 40 °C. Explain, using collision theory, why the reaction at 40 °C is faster. [4]
[4 marks]A student investigates the effect of temperature on the rate of decomposition of hydrogen peroxide. Explain why the rate approximately doubles for every 10 °C rise in temperature. [4]
[4 marks]Explain how an increase in temperature affects both the frequency of collisions AND the energy of collisions in a gas mixture. [4]
[4 marks]Using the concept of activation energy (Ea), explain why even a small rise in temperature can cause a large increase in reaction rate. [4]
[4 marks]A student writes: 'When temperature increases, particles move faster and collide more often, so the rate increases.' This answer scores only 1 mark out of 4. Explain what is MISSING from the student's answer.
[2 marks]A student says: 'At higher temperatures, the activation energy decreases, so more particles can react.' Identify the error and write a corrected statement.
[2 marks]Two students debate: Student A says 'temperature increases rate because particles have more energy'. Student B says 'temperature increases rate because particles collide more often'. Who is more correct? Explain.
[2 marks]A student writes: 'Increasing temperature makes particles react because they have more energy to break bonds.' Why would a Cambridge examiner penalise this answer?
[2 marks]An exam answer reads: 'At higher temperature, all particles have enough energy to react, so the rate is maximum.' Give TWO errors in this statement and explain the correct scientific understanding. [3]
[3 marks]Memorise this sequence. It is the blueprint for every temperature question on Papers 2, 4, and 6.
Sign In to Keep Going
You've reached the end of the free preview. Sign in — and upgrade to Plus or Pro — to keep going with Chemistry.
Full Access
Unlock all 320 lessons