How does an engineer choose the right material for a job?
Selecting a material by matching its properties to the product requirements, while balancing cost, availability, sustainability and aesthetics.
A focused answer to AQA GCSE Engineering on choosing materials by matching properties to function and weighing cost, availability, sustainability and aesthetics, using a clear selection method.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
AQA wants you to choose a material by matching its properties to what the product must do, then to justify the choice by weighing cost, availability, sustainability and how it looks. You should be able to discuss trade-offs, not just name a material, because the longer-mark questions reward balanced reasoning and a conclusion.
Start from the requirements
List what the product must do first. For a kettle: hold boiling water (so heat resistant and food safe), survive being dropped (tough), and look attractive. Each requirement points to a property, and only after the property list is clear can a sensible material be shortlisted. Starting from a material rather than the requirements is the most common way to make a poor choice.
The wider factors
These factors often pull in opposite directions, which is what makes selection a judgement rather than a lookup. A material with the best mechanical properties may be expensive, hard to source or energy-intensive to produce, while a cheaper material may need extra finishing or a heavier section to do the same job. Cost itself is not just the price per kilogram: a material that is awkward to machine or mould adds processing cost and scrap, so the cheapest raw material is not always the cheapest finished part. Sustainability has risen up the list as customers and regulations push for recyclable materials and lower carbon footprints, so a modern selection weighs the environmental impact across the whole life cycle alongside the traditional factors.
A simple selection method
- List the functional requirements.
- Identify the key properties each requirement needs.
- Shortlist materials that have those properties.
- Compare them on cost, availability, sustainability and aesthetics.
- Choose the best balance and justify it against the alternatives.
Try this
Q1. State two functional requirements you would list for a drinks bottle. [2 marks]
- Cue. Lightweight, food safe, tough or shatterproof, transparent, recyclable.
Q2. Name two wider factors (besides properties) that affect material choice. [2 marks]
- Cue. Any two of cost, availability, ease of manufacture, sustainability, aesthetics.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20196 marksA manufacturer must choose a material for an outdoor garden chair. Discuss the factors they should consider when selecting the material.Show worked answer →
A good answer covers properties and at least two wider factors with reasons, then judges.
The chair must carry a person's weight, so the material needs enough strength and stiffness. Because it is outdoors it must be corrosion or weather resistant (aluminium, treated steel or a UV-stable polymer).
Wider factors matter too: cost must suit the selling price; availability affects whether the material can be supplied in volume; sustainability (recyclability and carbon footprint) is increasingly important; and aesthetics influence whether customers buy it.
The best answers weigh these against each other, for example noting that aluminium is light, recyclable and weatherproof but costs more than treated steel, then reach a justified choice. Markers reward named properties tied to function plus a balanced discussion of cost, availability, sustainability and aesthetics.
AQA 20214 marksExplain why the strongest available material is not always the best choice for a product, using an example.Show worked answer →
A good answer shows that selection balances several factors, not strength alone.
The strongest material is often heavier, more expensive or harder to work than a weaker one that still meets the requirement. Selection is about meeting the specification at an acceptable cost, weight and impact, not maximising one property.
For example, a drinks bottle does not need the strength of steel; a tough, light, cheap, recyclable thermoplastic (PET) meets the requirement far better because it is lighter to transport, cheaper to make and recyclable, even though it is much weaker than steel.
Markers reward the point that the best choice meets the requirement at an acceptable cost and weight, supported by a sensible example.
Related dot points
- The main categories of engineering material (metals, polymers, ceramics, composites) and the mechanical, physical and aesthetic properties used to describe and compare them.
A focused answer to AQA GCSE Engineering on grouping materials into metals, polymers, ceramics and composites, and the key properties (strength, hardness, toughness, ductility, conductivity) used to compare them.
- Ferrous metals (contain iron) and non-ferrous metals, common examples and their properties, and why alloys are used to improve a base metal.
A focused answer to AQA GCSE Engineering on ferrous and non-ferrous metals and alloys, with common examples (mild steel, cast iron, aluminium, copper, brass) and their properties and uses.
- Thermoplastics and thermosetting polymers, their properties and uses, and how composites combine materials to give a better performance than either part alone.
A focused answer to AQA GCSE Engineering on thermoplastics, thermosetting polymers and composites, including common examples, properties, uses, and why composites such as GRP and CFRP outperform their parts.
- Smart materials that change a property in response to a stimulus, and modern materials developed through new processing, with examples and uses.
A focused answer to AQA GCSE Engineering on smart materials that respond to a stimulus (shape memory alloys, thermochromic and photochromic pigments, piezoelectric materials) and modern materials such as graphene, with their properties and uses.
Sources & how we know this
- AQA GCSE Engineering (8852) specification — AQA (2017)