What are the different types of oxides covered in the Cambridge IGCSE Coordinated Science syllabus?

In the Cambridge IGCSE Coordinated Science syllabus, oxides are classified into three main types: acidic oxides, basic oxides, and amphoteric oxides. Acidic oxides are typically non-metal oxides that react with water to form acids. Basic oxides are metal oxides that react with acids to form salts and water. Amphoteric oxides can react with both acids and bases to form salts and water.

How do acidic oxides differ from basic oxides in terms of chemical reactions?

Acidic oxides, usually formed from non-metals, react with water to produce acids. For example, sulfur dioxide (SO2) reacts with water to form sulfurous acid (H2SO3). Basic oxides, on the other hand, are typically metal oxides that react with acids to form salts and water. For instance, magnesium oxide (MgO) reacts with hydrochloric acid (HCl) to produce magnesium chloride (MgCl2) and water.

Can you explain what amphoteric oxides are with examples?

Amphoteric oxides are unique because they can react with both acids and bases to form salts and water. A common example is aluminum oxide (Al2O3). It reacts with hydrochloric acid (an acid) to form aluminum chloride and water, and with sodium hydroxide (a base) to form sodium aluminate and water. This dual behavior is a key characteristic of amphoteric oxides.

Why are some oxides considered neutral, and can you provide an example?

Neutral oxides are oxides that do not exhibit acidic or basic properties and do not react with acids or bases. They are relatively rare. An example of a neutral oxide is carbon monoxide (CO), which does not form salts or react with water to produce acids or bases.

How do the properties of oxides relate to their position in the periodic table?

The properties of oxides are closely related to the position of their elements in the periodic table. Generally, oxides of non-metals, found on the right side of the periodic table, tend to be acidic. Metal oxides, found on the left side, are usually basic. Elements near the metalloid line, such as aluminum, can form amphoteric oxides. Understanding these trends helps predict the behavior of oxides in chemical reactions.

Why is "Saying CO₂ is a basic oxide because it contains carbon (which can form a base)" a common mistake in Types of Oxides?

Why it happens: Students do not apply the rule that non-metal oxides are acidic. How to avoid it: CO₂ is a non-metal oxide → acidic. It reacts with alkalis, not acids. Recall: CO₂ + H₂O → H₂CO₃ (an acid).

Why is "Describing amphoteric oxides as 'neutral'" a common mistake in Types of Oxides?

Why it happens: Students confuse 'reacts with both' with 'neutral' (neither acidic nor basic). How to avoid it: Neutral oxides do NOT react with acids or alkalis (e.g. CO, NO). Amphoteric oxides react with BOTH (e.g. Al₂O₃, ZnO). They are not the same. Source: 0654 Examiner Report 2023

Why is "Saying the product of acid + basic oxide is acid + base" a common mistake in Types of Oxides?

Why it happens: Students do not remember that base + acid → salt + water. How to avoid it: Metal oxide (base) + acid → salt + water only. Never acid. Write the product as: name of metal + anion from acid.

Acids, Bases and SaltsCambridge IGCSE Coordinated Sciences 0654

Types of Oxides

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Types of Oxides — Cambridge IGCSE Coordinated Science 0654

Oxides are classified by their acid-base behaviour: acidic (react with bases), basic (react with acids), amphoteric (react with both), or neutral. Cambridge tests which type each oxide is and the pattern across the periodic table.

What you’ll learn

Mapped to the Cambridge IGCSE 0654 syllabus (2025-2027).

C8.5 — Classify oxides as acidic, basic, amphoteric, or neutral.
C8.6 — Write equations for reactions of acidic and basic oxides.
C8.7 — Describe the trend in oxide character across Period 3.

Types of Oxides

Oxides are classified by their reactions with acids and bases. The classification follows position in the periodic table.

Type	Description	Examples	Reaction
Acidic oxide	React with bases/alkalis to form salt + water. Many dissolve in water to form acids.	CO₂, SO₂, SO₃, NO₂, P₂O₅	CO₂ + 2NaOH → Na₂CO₃ + H₂O
Basic oxide	React with acids to form salt + water. Metal oxides.	Na₂O, CuO, MgO, Fe₂O₃, CaO	CuO + H₂SO₄ → CuSO₄ + H₂O
Amphoteric oxide	React with BOTH acids AND bases to form salt + water.	Al₂O₃, ZnO, PbO, Cr₂O₃	Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O; Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O
Neutral oxide	React with neither acids nor bases	CO, NO, H₂O, N₂O	—

Periodic trend in Period 3 (Na to Ar): Na₂O → MgO (basic) → Al₂O₃ (amphoteric) → SiO₂ (weakly acidic) → P₂O₅, SO₃, Cl₂O₇ (acidic) → Across the period: basic → amphoteric → acidic

Acidic oxides + water:

CO₂ + H₂O → H₂CO₃ (carbonic acid)
SO₃ + H₂O → H₂SO₄ (sulfuric acid) — industrial acid rain
SO₂ + H₂O → H₂SO₃ (sulfurous acid)

Acidic oxides: non-metals. Basic oxides: metals. Amphoteric: react with both (Al₂O₃, ZnO).
Period 3 trend: basic → amphoteric → acidic (left to right).
SO₃ + H₂O → H₂SO₄ (related to acid rain).

How it’s examined

Paper 4: 'Classify aluminium oxide as acidic, basic, amphoteric, or neutral and give evidence' (2 marks — amphoteric, reacts with both acids and bases). 'Write equations for the reactions of ZnO with sulfuric acid AND with sodium hydroxide' (2 marks each). MCQ tests classifying an oxide from its formula.

Sources: Cambridge IGCSE Coordinated Sciences 0654 syllabus 2025-2027 (C8); 0654 Examiner Reports 2022-2024. Last reviewed 2026-05-14.

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Step-by-step worked examples — Types of Oxides

Step-by-step solutions to past-paper-style questions on types of oxides, written exactly the way a tutor would explain them at the board.

1Acidic oxide — reaction of SO₂ with NaOH
Extended
Question
State the type of oxide of sulfur dioxide (SO₂) and write the equation for its reaction with sodium hydroxide solution.
Step-by-step solution
1. Step 1
  SO₂ is formed from sulfur (a non-metal); non-metal oxides are acidic oxides.
2. Step 2
  Acidic oxides react with alkalis (NaOH) to form a salt and water.
  $\text{SO}_2 + 2\text{NaOH} \rightarrow \text{Na}_2\text{SO}_3 + \text{H}_2\text{O}$
Answer
SO₂ is an acidic oxide. $\text{SO}_2 + 2\text{NaOH} \rightarrow \text{Na}_2\text{SO}_3 + \text{H}_2\text{O}$
2Identifying an amphoteric oxide
Core
Question
Aluminium oxide reacts with both dilute hydrochloric acid and sodium hydroxide solution. What type of oxide is this?
Step-by-step solution
1. Step 1
  A substance that reacts with both acids and bases is described as amphoteric.
2. Step 2
  Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O (reacts as a base with acid).
3. Step 3
  Al₂O₃ + 2NaOH + 3H₂O → 2NaAl(OH)₄ (reacts as an acid with base).
Answer
Aluminium oxide is an amphoteric oxide — it reacts with both acids and bases.
3Why CO₂ is an acidic oxide
Extended
Question
Explain why carbon dioxide is described as an acidic oxide.
Step-by-step solution
1. Step 1
  CO₂ is a non-metal oxide (carbon is a non-metal); non-metal oxides are typically acidic.
2. Step 2
  CO₂ dissolves in water to form carbonic acid (pH < 7).
  $\text{CO}_2 + \text{H}_2\text{O} \rightarrow \text{H}_2\text{CO}_3$
3. Step 3
  CO₂ also reacts with alkalis (bases) to form a salt: CO₂ + 2NaOH → Na₂CO₃ + H₂O.
Answer
CO₂ is a non-metal oxide; dissolves in water to form an acid (H₂CO₃) and reacts with alkalis to form salts → acidic oxide.
4Basic oxide reacting with an acid
Core
Question
Write a balanced equation for the reaction of copper(II) oxide with dilute sulfuric acid.
Step-by-step solution
1. Step 1
  CuO is a basic oxide (metal oxide). It reacts with an acid to form a salt and water.
  $\text{CuO} + \text{H}_2\text{SO}_4 \rightarrow \text{CuSO}_4 + \text{H}_2\text{O}$
2. Step 2
  Check balance: Cu 1=1; O 2=2 (1 from CuO + 4 from H₂SO₄ = 1 in CuSO₄ + 1 in H₂O + 3 in SO₄); H 2=2. ✓
Answer
$\text{CuO} + \text{H}_2\text{SO}_4 \rightarrow \text{CuSO}_4 + \text{H}_2\text{O}$

Key Definitions and Keywords — Types of Oxides

Definitions to memorise and the exact keywords mark schemes credit for types of oxides answers — sharpened from recent examiner reports for the 2026 Cambridge IGCSE sitting.

Acidic oxide
Examiner keyword
A non-metal oxide that reacts with water to form an acid, and/or reacts with a base/alkali to form a salt. Examples: CO₂, SO₂, SO₃, NO₂.
Basic oxide
Examiner keyword
A metal oxide that reacts with an acid to form a salt and water only. Most are insoluble in water; those that dissolve form alkalis.
Example
CuO, MgO, CaO, Na₂O, Fe₂O₃.
Amphoteric oxide
Examiner keyword
An oxide that reacts with both acids and alkalis to form a salt and water. Examples: Al₂O₃, ZnO, PbO.
Neutral oxide
Examiner keyword
An oxide that is neither acidic nor basic; does not react with acids or alkalis. Examples: water (H₂O), carbon monoxide (CO), nitrogen monoxide (NO).
Alkali from a basic oxide
When a soluble metal oxide dissolves in water, it forms an alkali (e.g. Na₂O + H₂O → 2NaOH); most metal oxides are insoluble and do not dissolve.

Common Mistakes and Misconceptions — Types of Oxides

The traps other students keep falling into on types of oxides questions — taken from recent Cambridge IGCSE examiner reports and mark schemes — and how to avoid them.

✕Saying CO₂ is a basic oxide because it contains carbon (which can form a base)
Why it happens
Students do not apply the rule that non-metal oxides are acidic.
How to avoid it
CO₂ is a non-metal oxide → acidic. It reacts with alkalis, not acids. Recall: CO₂ + H₂O → H₂CO₃ (an acid).
✕Describing amphoteric oxides as 'neutral'
0654 Examiner Report 2023
Why it happens
Students confuse 'reacts with both' with 'neutral' (neither acidic nor basic).
How to avoid it
Neutral oxides do NOT react with acids or alkalis (e.g. CO, NO). Amphoteric oxides react with BOTH (e.g. Al₂O₃, ZnO). They are not the same.
✕Saying the product of acid + basic oxide is acid + base
Why it happens
Students do not remember that base + acid → salt + water.
How to avoid it
Metal oxide (base) + acid → salt + water only. Never acid. Write the product as: name of metal + anion from acid.

Practice questions

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Types of Oxides — frequently asked questions

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Types of Oxides

Short Study Notes in the form of Slides

Short Study Notes — Types of Oxides

Detailed Notes

What you’ll learn

How it’s examined

1Acidic oxide — reaction of SO₂ with NaOH

2Identifying an amphoteric oxide

3Why CO₂ is an acidic oxide

4Basic oxide reacting with an acid

Acidic oxide

Basic oxide

Amphoteric oxide

Neutral oxide

Alkali from a basic oxide

✕Saying CO₂ is a basic oxide because it contains carbon (which can form a base)

✕Describing amphoteric oxides as 'neutral'

✕Saying the product of acid + basic oxide is acid + base

Practice questions

Past paper style quiz

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Types of Oxides — frequently asked questions