Core5 mapped NDA questions
Build the idea
Build exam-ready understanding by connecting the core idea, formulas or facts, worked example and previous NDA questions. Focus on why each rule works, then test it under timed conditions.
Concept
A physical change alters only the form or state of a substance, with no new substance formed, and is usually reversible. A chemical change produces one or more new substances and is generally irreversible.
Identifying which type a process is, is a common question.
Key Points & Formulas
- Physical change: melting of ice, boiling water, dissolving salt (reversible, no new substance).
- Chemical change: burning, rusting, cooking, digestion (new substance, often irreversible).
- Signs of a chemical change: gas evolved, colour change, heat/light, precipitate.
- Mass is conserved in both types of change.
Worked Example
Q. Classify: (i) melting of wax, (ii) burning of wax.
Melting of wax changes only its state (solid→liquid) — physical change.
Burning of wax forms CO₂ and water vapour — a chemical change.