Oxidation and reduction in terms of oxygen, hydrogen, electrons and oxidation number, oxidising and reducing agents, redox equations and tests for oxidising and reducing agents.
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.
Rusting, burning, bleaching and the batteries in your phone are all redox reactions. Learning the electron story behind them makes them easy to predict.
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.
Gain of oxygen / loss of hydrogen / loss of electrons / oxidation number increases.
Loss of oxygen / gain of hydrogen / gain of electrons / oxidation number decreases.
Oxidation Is Loss, Reduction Is Gain (of electrons).
Elements 0; ions = charge; H +1; O −2; sum = charge.
Accepts electrons; is reduced.
Donates electrons; is oxidised.
KMnO₄ purple → colourless; K₂Cr₂O₇ orange → green (reducing agents); KI → brown (oxidising agents).
More reactive metal or halogen displaces a less reactive one.
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 copper(II) sulfate solution: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s).
(a) (a) Define oxidation and reduction in terms of electrons. [2]
(b) (b) Write half-equations for the oxidation and the reduction. [2]
(c) (c) Identify the oxidising agent and the reducing agent, with a reason. [4]
(d) (d) State two observations when a zinc strip is placed in blue copper(II) sulfate solution. [2]
(e) (e) Deduce the oxidation number of manganese in KMnO₄ and chromium in K₂Cr₂O₇. [2]
(f) (f) Describe a test to show that a gas is a reducing agent, such as sulfur dioxide. [3]
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.