What rate of reaction means, how it is measured, how concentration, temperature, surface area and catalysts change it, why (collision theory), and how to interpret rate graphs.
5 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
Why do we keep food in the fridge, crush tablets before swallowing them, and use catalysts in car exhausts? All of it is about controlling the speed of reactions.
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Copy these into your notebook in your own words — that is how they stick.
Change in amount or concentration of reactant or product per unit time.
Gas volume, mass loss, time for a mark to disappear.
Concentration/pressure, temperature, surface area, catalyst.
Rate depends on the number of SUCCESSFUL collisions per second.
Minimum energy for a successful collision.
Lowers the activation energy; not used up.
Steeper = faster; gradient = rate; flat = finished.
Control all variables except the one being changed.
3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness. More games in the Chemistry Arcade.
8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better. Work each item on paper first.
Write full answers, then reveal the mark scheme and tick the points you earned (15 marks in total). Show all your working — method marks count. Your answers are saved on this device.
Question 1 [15 marks]
Zinc reacts with dilute hydrochloric acid: Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g). A student measures the volume of hydrogen produced in 2 minutes using acid of different concentrations.
(a) (a) Define rate of reaction. [2]
(b) (b) Draw a labelled diagram of apparatus to collect and measure the volume of hydrogen. [3]
(c) (c) State the manipulated, responding and two controlled variables. [4]
(d) (d) Explain, using collision theory, why increasing the concentration increases the rate. [3]
(e) (e) State one precaution to take and give a reason. [2]
(f) (f) Describe how the volume–time graph would differ if zinc powder were used instead of zinc granules. [1]
Find these in your own past-paper booklets for extra timed practice. Items above are written in the style of these papers; any adapted from a specific question say so.