Interactive Lesson · 7.2.1 Core
Acidic & Basic Oxides
The Periodic Table's Great Turf War — Metal vs Non-metal
⚔️ The Periodic Table Turf War
🔵 BLUE TEAM — Metals
Left side of the table
→ Form BASIC oxides
e.g. CaO, MgO, Na₂O, CuO
They neutralise acids ⚡
🔴 RED TEAM — Non-metals
Right side of the table
→ Form ACIDIC oxides
e.g. SO₂, CO₂, NO₂, P₄O₁₀
They neutralise alkalis ⚡
💡 The Golden Rule: Look at the first element. Is it a metal? → BASIC. Non-metal? → ACIDIC.
🧪 Virtual Gas Bubbler
Watch the Universal Indicator change colour as oxide gases dissolve in water.
CO₂ (Acidic Oxide)
CO₂ + H₂O → H₂CO₃
Carbonic acid forms → pH drops
Carbonic acid forms → pH drops
CaO (Basic Oxide)
CaO + H₂O → Ca(OH)₂
Calcium hydroxide forms → pH rises
Calcium hydroxide forms → pH rises
🏭 Oxide Sorter — The Conveyor Belt
Sort each oxide into the correct bin. Tip: First element = metal? → BASIC. Non-metal? → ACIDIC.
✅ Sorted: 0/8Correct: 0/8
Next on the belt:
MgO
Magnesium oxide
First element: Mg (Metal)
🌾 The Farmer's Crisis — Fix the Soil!
Your crops are dying because the soil is too acidic. Which oxide do you add to neutralise it?
Soil pHDangerously Acidic! ☠️ pH 4
pH 0 (acid)pH 7 (neutral)pH 14 (alkali)
Choose an oxide to add to the soil:
🌧️ Acid Rain — The Environmental Link
Non-metal oxides from human activity dissolve in clouds to form acid rain. Click a source to see the chemistry.
⚠️ Examiner Traps — Don't Lose Marks!
✗
Carbon monoxide (CO) is NEUTRAL, not acidic
CO does NOT dissolve in water to form an acid — it's an exception!
✗
Water (H₂O) is a special case — it's an oxide but neither acidic nor basic on its own
H₂O is amphoteric, but IGCSE treats it as neutral
✗
Na₂O is not written as NaO
Sodium is Na⁺ (charge 1+), oxide is O²⁻ (charge 2–), so you need 2 Na to balance: Na₂O
✗
An oxide neutralising an acid or alkali does NOT mean it is itself an acid or alkali
A basic oxide like CuO is NOT an alkali. Only its solution/product may be alkaline.
📋 Key Equations Summary
Basic oxide + acid →
CuO(s) + H₂SO₄(aq) → CuSO₄(aq) + H₂O(l)
Basic oxide + water →
CaO(s) + H₂O(l) → Ca(OH)₂(aq)
Acidic oxide + alkali →
CO₂(g) + 2NaOH(aq) → Na₂CO₃(aq) + H₂O(l)
Acidic oxide + water →
SO₂(g) + H₂O(l) → H₂SO₃(aq)
Always include state symbols (s), (l), (g), (aq) for full marks in Paper 4!
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