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IGCSE · Practice questions · Physical and chemical changes

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Six original Cambridge-style questions on physical and chemical changes: definitions, examples and the evidence that a new substance has formed.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
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01
Recall
[2 marks]

State two differences between a physical change and a chemical change.

  • A chemical change forms a new substance; a physical change does not. ✓
  • A physical change is usually easy to reverse; a chemical change usually is not (and often has a larger energy change). ✓
02
Analysis
[4 marks]

Classify each change as physical or chemical: (a) wax melting, (b) wax burning, (c) iron rusting, (d) water evaporating from a puddle.

  • (a) physical ✓
  • (b) chemical ✓
  • (c) chemical ✓
  • (d) physical ✓
03
Explain
[2 marks]

Explain why dissolving sugar in water is a physical change.

  • No new substance is formed; the sugar molecules are only spread out among the water molecules. ✓
  • The sugar can be recovered unchanged by evaporating the water. ✓
04
Recall
[3 marks]

Give three observations that could show a chemical change has taken place.

  • A gas is given off (fizzing). ✓
  • A precipitate forms, or there is a colour change that does not reverse. ✓
  • The temperature changes without external heating or cooling. ✓
05
Explain
[2 marks]

When magnesium ribbon is heated it burns with a bright white flame and leaves a white powder. Explain why this is a chemical change.

  • A new substance, magnesium oxide (the white powder), is formed. ✓
  • Energy is given out as heat and light, and the change cannot easily be reversed. ✓
06
Explain
[2 marks]

A student says that heating ice until it melts is a chemical change because energy is taken in. Explain why the student is wrong.

  • Energy changes happen in physical changes too, so an energy change alone does not show a chemical change. ✓
  • Liquid water is still H2O; no new substance forms, so melting is a physical change. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.