Explaining what's happening
3 marks · NormalA student investigates the reaction between sodium thiosulfate and hydrochloric acid at two different temperatures. The reaction is much faster at 45°C than at 25°C. Explain, using collision theory, why increasing the temperature increases the rate of this reaction.
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Also accept: Particles move faster with higher temperature; More collisions per second and more energetic collisions
Common mistakes: Saying just 'temperature increases rate' with no explanation; Not mentioning energy of collisions
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Marking points
M1 · 1 mark · States that higher temperature increases the speed of particles
M2 · 1 mark · States that there are more collisions or more frequent collisions
A1 · 1 mark · States that more collisions have enough energy to be successful/exceed activation energy, or more successful collisions
Worked solution
Increasing the temperature increases the speed of the particles, so they move faster. This causes the particles to collide more often. Also, a higher proportion of collisions have energy equal to or greater than the activation energy, so there are more successful collisions per second and the rate increases.