The big idea: Identifying the most suitable material is a complex and challenging task.
Not because the data is hard to find — because the requirements conflict. Light fights heat-resistant; warm-looking fights damp-proof. No candidate wins every row.
Four candidates, six requirements. Watch the score change as each family is applied — and notice no column is all ticks.
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What goes into the decision
Physical properties
Density, melting point, conductivity. These usually set hard limits — a material that softens at the working temperature is simply out.
Chemical properties
Corrosion, food safety, moisture, fire. These are about the environment the product lives in, and they eliminate rather than rank.
Mechanical properties
Strength, stiffness, toughness, hardness. These decide whether it survives the forces of use — and often several candidates pass.
Aesthetic characteristics
Colour, texture, lustre, how it ages. The guide names these alongside the three families — and unlike them, they cannot be looked up.
Why aesthetics behave differently: The three property families are measured. Aesthetic characteristics are judged — against the brief, the user and the market. That is what makes the final call a design decision rather than a calculation.
Three choices, explained property by property
Glass for office walls
Transparency lets daylight in and people see out, so glass is chosen even though it is heavy and brittle.
Synthetic fibres for tents
Nylon and polyester are waterproof (with a coating), do not rot and are light for their strength, unlike cotton canvas.
ABS for a toy
Mechanical: tough, so it survives drops. Physical: light. Aesthetic: takes bright colours and a smooth finish.
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When requirements conflict, a designer decides which are non-negotiable and which can be traded. The answer that earns marks says so explicitly.
Non-negotiable
- Anything about safety — food contact, flammability, electrical insulation
- Anything that would make the product fail in use
- Anything a standard or regulation requires
- If a material fails one of these it is eliminated, whatever else it offers
Tradeable
- Weight, when the product is not carried far
- Appearance, when the part is hidden
- Cost, within the brief's limits
- These get ranked rather than used to eliminate
The trap: Answering "the best material is X" with no reasoning about what was traded away. Evaluate questions are marked on the weighing, not the winner.
How this is tested — evaluating properties to select the most appropriate material. It comes up two ways:
Paper 1 — multiple choice
- Identify the property that eliminates a candidate.
- Pick the material that best meets stated requirements.
Paper 2 — analysing a product
- Evaluate two candidate materials for a named product.
- Justify a material choice against conflicting requirements.
The trap: Treating selection as a lookup. Say which requirements are non-negotiable, which you traded, and why — that is the reasoning the marks are for.
A company is choosing between bamboo and stainless steel for the handles of a premium kitchen utensil range. Evaluate the two.
Model answer plan
See the answer broken into clear points, with guidance on how each point earns marks.