Who this is for: Cambridge IGCSE Chemistry (0620) students who want physical and chemical changes — telling them apart, spotting new substances and linking to reversibility — to become reliable marks instead of vague definitions they cannot apply.
What query it owns: how to understand and revise physical and chemical changes in Cambridge IGCSE Chemistry.
Why this is safe: this page owns the physical and chemical changes revision-guide angle, while Tutopiya’s Physical and Chemical Changes subtopic page owns the learning resource and the free Physical and Chemical Changes quiz owns the practice.

Physical and chemical changes sit at the foundation of the Chemical Reactions unit in Cambridge IGCSE Chemistry (0620). Examiners expect you to state whether a change is physical or chemical, explain how you know a new substance has formed, and distinguish reversible from irreversible changes. This guide covers the syllabus definitions, the evidence examiners look for, and the question types that appear every year.

Key takeaways

• A physical change does not produce a new substance — only the state or appearance changes.
• A chemical change produces a new substance with different properties.
• Evidence of a chemical change includes colour change, gas evolved, temperature change and precipitate formed.
• Reversible changes can be undone; irreversible chemical changes cannot return to the original substances.

What are physical and chemical changes in Cambridge IGCSE Chemistry?

A physical change alters the form of a substance without changing its chemical identity — melting ice, dissolving sugar or crushing a solid are physical changes. A chemical change produces one or more new substances through a chemical reaction — burning magnesium, rusting iron or neutralising an acid are chemical changes. The syllabus requires you to classify changes correctly and give evidence when a new substance has formed.

You can read the full explanation, worked examples and notes on Tutopiya’s Physical and Chemical Changes subtopic page before you attempt questions.

The core ideas you must master

Idea	What it means	How the exam uses it
Physical change	No new substance; often reversible	”State whether melting is physical or chemical.”
Chemical change	New substance formed	”Explain how you know a chemical change occurred.”
Evidence	Colour, gas, temperature, precipitate	”Give two pieces of evidence for a chemical reaction.”
Reversible	Change can be undone	”Is dissolving salt reversible?”
Irreversible	Cannot return to original	”Is burning wood reversible?”

Physical vs chemical: which type is the change?

Use the table to classify common examples quickly.

Change	Type	Reason
Melting ice	Physical	H₂O remains H₂O — only state changes
Boiling water	Physical	Still water vapour (H₂O)
Dissolving salt in water	Physical	Ions separate but no new substance
Burning magnesium	Chemical	New substance (magnesium oxide) formed
Rusting iron	Chemical	Iron oxide formed
Neutralising acid with alkali	Chemical	Salt and water formed
Electrolysis of water	Chemical	H₂ and O₂ gases produced

How to identify a chemical change — step by step

1. Look for a new substance — different colour, different properties or a formula change.
2. Check for evidence — gas bubbles, temperature rise/fall, precipitate or permanent colour change.
3. Ask if it is reversible — if you cannot get the original substances back easily, it is likely chemical.
4. State your conclusion with one piece of evidence in exam answers.

Once you have worked through a few, test yourself with the free Physical and Chemical Changes quiz — it tells you fast whether the definitions have actually stuck.

Physical and chemical changes in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical changes stem
Define	Precise syllabus definition	”Define a chemical change.”
State	Short factual answer	”State whether boiling is a physical or chemical change.”
Explain	Reason with evidence	”Explain how you know a chemical change has occurred.”
Give an example	Named change with classification	”Give an example of a reversible physical change.”
Distinguish	Compare two types	”Distinguish between a physical and a chemical change.”

Worked exam-style stems (how to answer the wording)

1. “Define a chemical change.” A change in which one or more new substances are formed. Mark-scheme reward: new substance(s) formed.
2. “State whether melting wax is a physical or chemical change. Explain your answer.” Physical — wax remains wax; only the state changes from solid to liquid. No new substance is formed. Reward: correct classification + no new substance.
3. “A colourless solution turns blue and a gas is evolved. Explain why this is a chemical change.” A new substance has formed (colour change from colourless to blue) and gas evolved — both are evidence of a chemical reaction. Reward: new substance + named evidence.

When you can recognise the wording instantly, work the full set on the Chemical Reactions topical past paper questions and the Physical and Chemical Changes quiz to lock the definitions in.

How physical and chemical changes connect to the rest of Chemical Reactions

Physical and chemical changes feed directly into Rate of Reaction and Reversible Reactions and Equilibrium. When you are ready to mix topics, the Cambridge IGCSE Chemistry resource hub links every Chemical Reactions subtopic.

Common mistakes students make

• Calling dissolving always physical without checking if a reaction occurs (e.g. acid + metal is chemical).
• Saying boiling is chemical because bubbles appear (bubbles are just steam — still H₂O).
• Giving “energy change” alone as evidence without mentioning a new substance.
• Confusing reversible physical changes (freezing) with reversible chemical reactions (equilibrium).
• Describing crushing a tablet as chemical (it is physical — same substance, smaller pieces).

When you need more support

If physical and chemical change questions keep costing marks — especially explain questions needing evidence — work through the Chemical Reactions topical past paper questions and the Physical and Chemical Changes quiz, then get focused help from a Cambridge IGCSE Chemistry tutor.

Frequently asked questions

Is physical and chemical changes hard in Cambridge IGCSE Chemistry? The definitions are straightforward. Marks are lost when students cannot give evidence of a new substance or misclassify boiling and melting.

What is the quickest way to tell a chemical change? Look for a new substance — shown by permanent colour change, gas evolved, precipitate or temperature change that indicates a reaction.

Is dissolving always a physical change? Dissolving without reaction (e.g. sugar in water) is physical. If a new substance forms (e.g. acid reacting with metal), it is chemical.

How do I revise physical and chemical changes effectively? Learn the definitions, classify ten everyday examples, then take the Physical and Chemical Changes quiz.

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