This exam focus covers Worked Model Answer within Rates & Collision Theory for GCSE Chemistry. Revise Rates & Collision Theory in Rates of Reaction for GCSE Chemistry with 25 exam-style questions and 16 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 13 of 14 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
📝 Worked Model Answer
Question: "Explain why increasing the temperature increases the rate of reaction." (4 marks)
When the temperature increases, the particles gain more kinetic energy and move faster. [1] This means the particles collide more frequently — more collisions occur per second because the particles are moving around more quickly. [1] In addition, a greater proportion of the particles now have energy greater than or equal to the activation energy. [1] As a result, more collisions are successful — they lead to a reaction — so the rate of reaction increases. [1]
Examiner note: This question has four distinct mark points and students must address all four for full marks. The most common mistake is stopping after "particles move faster" and "collide more often" — this only scores 2 marks. The third and fourth points (more particles exceed activation energy, therefore more successful collisions) are essential and are the marks that separate grade 6 from grade 7-9 answers. Avoid vague phrases like "particles have more energy" without specifying kinetic energy.
Practice questions for Rates & Collision Theory
According to collision theory, which of the following must happen for a chemical reaction to take place?
Explain, using collision theory, why increasing the concentration of a reactant solution increases the rate of reaction.