Key Idea: Materials are classified two ways, and an exam question will tell you which it wants: by source (natural or human-made) or by property family (physical, chemical, mechanical). Physical is what the material IS. Chemical is what it REACTS WITH. Mechanical is how it behaves UNDER LOAD. Selecting a material is a trade-off: requirements, properties, cost, availability, aesthetics and environmental impact never all point the same way. Composites combine a matrix and a reinforcement so the pair beats either alone. Smart materials change a property in response to a stimulus. Biodegradable materials are designed to break down into substances that rejoin natural cycles.
Paper 1 — multiple choice
- Put a named property in the right family
- Classify a material as natural or human-made
- Identify the stimulus a smart material responds to
- Pick the constituent doing the work in a composite
Paper 2 — analysing a product
- Explain why a property matters for a named part
- Justify a material choice against a requirement
- Explain a composite in terms of matrix and reinforcement
- Evaluate a biodegradable material for a real product
Carried into the design project
- Criterion D — your material choice must be justified, not stated
- Criterion E — the environmental cost of the material you chose
- Every specification line needs a measurable property behind it
Students lose marks here by answering the classification they revised rather than the one that was asked. The wording gives it away every time.
| If the question says… | It wants… | Answer in these words |
|---|---|---|
| "where it comes from", "source", "origin" | Natural or human-made | Natural: timbers, textiles, biomaterials. Human-made: metals, polymers, ceramics, composites |
| "property", "behaviour", "characteristic" | Physical, chemical or mechanical | Physical is what it IS, chemical what it REACTS WITH, mechanical how it behaves UNDER LOAD |
| "why this material", "justify" | A trade-off against a requirement | Requirement → property → the number or the consequence |
One material sits in both classifications at once. Read the question for which axis it is asking about.
🔒 Interactive diagram
Explore the labelled diagram, charts and maps for this topic in study mode.
Ask what you would have to DO to measure it. Weigh it, heat it or pass current through it — physical. Leave it somewhere and wait — chemical. Pull it, bend it or hit it — mechanical. Hardness is the one that trips people: you press an indenter into it, so it is mechanical.
| Family | Properties | What a designer does with it |
|---|---|---|
| Physical | Mass, weight, volume, density, melting point, thermal and electrical conductivity, thermal expansion | Decides how heavy the product is for its size, what temperature it survives, and whether it insulates or conducts |
| Chemical | Oxidation, corrosion resistance, reaction to solvents and to UV, flammability, toxicity | Decides whether the product survives its ENVIRONMENT — rain, salt, cleaning chemicals, sunlight |
| Mechanical | Tensile and compressive strength, stiffness, hardness, toughness, ductility, malleability, elasticity, plasticity, fatigue | Decides whether the product survives its LOADS — being stood on, dropped, or flexed a million times |
Important: Strength vs stiffness — strength is the load before it breaks; stiffness is how little it bends before then. A fishing rod is strong and not stiff. Hardness vs toughness — hardness resists scratching; toughness resists cracking. Glass is hard and not tough. Ductility vs malleability — ductile draws into a WIRE; malleable rolls into a SHEET. Elasticity vs plasticity — elastic springs back; plastic stays where you put it.
Each mechanical property drawn as the test that measures it — because that is the form the exam question takes.
🔒 Interactive diagram
Explore the labelled diagram, charts and maps for this topic in study mode.
A manufacturer replaces the aluminium frame of a folding camping chair with a glass-fibre reinforced polymer. Explain the consequences for the user, referring to one physical, one chemical and one mechanical property.
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
A hospital replaces the stainless steel handle on a ward door with a copper alloy handle. Justify this choice using material properties.
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
A garden furniture range is relaunched using a biodegradable polymer. Outline why this may not reduce the product's environmental impact.
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Which family does hardness belong to, and why does it catch people out?
In a composite, what does each constituent do?
What makes a material smart rather than just useful?
Which natural families does the guide name?
Why is density more useful to a designer than mass?
A material is described as tough but not hard. What does that mean in use?
Exam tips
- Read which classification is wanted: source or property family. Answering the other one scores nothing.
- Every property mark needs a consequence. "It is dense" is half an answer; "it is dense, so the base does not tip" is the whole one.
- For a composite, always name matrix and reinforcement and say what each does.
- For a smart material, give the stimulus as well as the response. Piezoelectricity with no squeeze earns nothing.
- Biodegradable is a condition: state the conditions it needs and whether the product will ever meet them.
- For justify, name the trade-off you are accepting. An answer with no cost side reads as a sales pitch.