What is the difference between a mechanical and a physical property of a material?

A mechanical property describes how a material behaves under a force, such as strength, hardness, toughness, ductility, malleability and elasticity. A physical property describes a characteristic that does not involve an applied force, such as density, electrical and thermal conductivity, melting point and appearance. Both matter in design: mechanical properties decide whether a part survives loads, while physical properties decide things like weight, insulation and aesthetics.

How are woods classified in Design and Technology?

Woods are classified as hardwoods (from broad-leaved, usually slower-growing deciduous trees such as oak and mahogany), softwoods (from coniferous trees such as pine, generally faster-growing and cheaper), and manufactured boards (made by gluing wood fibres, particles or veneers, such as plywood, MDF and chipboard). Manufactured boards come in large, stable, uniform sheets, which is why they are widely used in furniture.

What is the difference between ferrous and non-ferrous metals?

Ferrous metals contain iron and are usually magnetic and prone to rust, for example mild steel and cast iron. Non-ferrous metals contain no iron, so they do not rust in the same way and are usually non-magnetic, for example aluminium, copper and brass. An alloy is a mixture of two or more metals (or a metal and another element) made to improve properties, such as steel, which is iron alloyed with carbon.

What is the difference between a thermoplastic and a thermosetting plastic?

A thermoplastic softens when heated and can be reshaped and recycled many times, for example acrylic, polypropylene and PVC. A thermosetting plastic undergoes a permanent chemical change when first set, so it cannot be softened and reshaped by heating again, for example melamine and epoxy resin. Thermoplastics suit reshaping and recycling; thermosets suit heat-resistant, rigid applications such as electrical fittings.

How does a designer select the right material for a product?

By balancing several factors together: the functional properties needed (strength, hardness, conductivity and so on), aesthetics, cost, ease of manufacture and environmental impact, and then justifying the choice against the product's requirements. No single factor decides it; the best material is the one that meets the specification while keeping cost, manufacture and sustainability acceptable, so the choice must always be reasoned and explained.

SingaporeDesign and Technology

Materials and Their Properties: how Singapore O-Level Design and Technology students classify woods, metals and plastics, understand mechanical and physical properties, and select the right material for a product

A Singapore O-Level Design and Technology (SEAB 7059) module overview of materials. Mechanical and physical properties, woods and manufactured boards, ferrous and non-ferrous metals and alloys, thermoplastics and thermosets, and balancing properties, cost and impact to select a material, with links to every dot point.

Generated by Claude Opus 4.87 min readSEAB-7059Updated 2026-06-13

Reviewed by: AI editorial process; not yet individually human-reviewed

Jump to a section

What this module covers
The vocabulary of properties
Woods and manufactured boards
Metals and alloys
Plastics
Pulling it together: selection
How this module is examined
Check your knowledge

What this module covers

Materials and Their Properties is the knowledge base that makes every other decision in Design and Technology possible. In O-Level Design and Technology (SEAB 7059), you must know the main families of material, what their properties mean, and how to choose between them for a real product. This content is heavily tested in the written paper and is decisive in the Design Project, where a justified material choice underpins the whole artefact. This overview links the five dot points: properties, woods, metals, plastics, and selection.

See the full set of dot points for this module under /sg-o-level/design-and-technology/syllabus/materials-and-their-properties.

The vocabulary of properties

You cannot compare materials without the right words. The mechanical and physical properties dot point defines and distinguishes strength, hardness, toughness, ductility, malleability, elasticity, density and durability, and relates each to design choices. Mechanical properties describe behaviour under force; physical properties describe characteristics like density and conductivity that do not involve an applied force.

Woods and manufactured boards

The woods and manufactured boards dot point classifies woods as hardwoods (broad-leaved trees such as oak and mahogany), softwoods (conifers such as pine) and manufactured boards (plywood, MDF, chipboard). Manufactured boards come in large, stable, uniform sheets, which is why they dominate flat-pack furniture, while natural timbers offer grain and strength along the fibres.

Metals and alloys

The metals, ferrous and non-ferrous dot point classifies metals as ferrous (containing iron, usually magnetic and prone to rust, such as mild steel), non-ferrous (no iron, such as aluminium and copper) and alloys (mixtures made to improve properties, such as steel and brass). Knowing why alloys are made, to gain strength, corrosion resistance or workability, is a frequently tested idea.

Plastics

The plastics, thermoplastics and thermosets dot point draws the central distinction: thermoplastics soften on heating and can be reshaped and recycled (acrylic, polypropylene, PVC), while thermosetting plastics set permanently and cannot be remelted (melamine, epoxy). This difference drives both how a plastic is processed and whether it can be recycled, linking directly to sustainability.

Pulling it together: selection

All the property knowledge converges on one decision. Selecting the right material balances functional properties, aesthetics, cost, ease of manufacture and environmental impact, with each choice justified against the product's requirements. No single factor wins; the skill is weighing them and explaining the trade-off.

Choosing a material for an outdoor bench frame

A park bench frame must be strong, weather-resistant, reasonably light and affordable, and easy to fabricate in a school workshop.

Step 1: List the required properties

Strength to carry users, corrosion resistance for outdoor use, moderate weight for handling, low cost, and workability with school equipment.

Step 2: Shortlist candidate materials

Mild steel (ferrous): strong, cheap, easy to weld, but rusts unless protected. Aluminium (non-ferrous): light and corrosion-resistant, but dearer and harder to weld at school. Hardwood such as teak: weather-resistant and attractive, but expensive.

Step 3: Weigh the trade-offs

Mild steel meets strength and cost and is easy to fabricate, and its one weakness (rust) can be solved with a finish. Aluminium avoids rust but costs more and is harder to join. Teak is excellent outdoors but too expensive for the budget.

Step 4: Justify the selection

Choose mild steel, protected with a galvanised or powder-coated finish. It satisfies strength, cost and workability, and the corrosion weakness is removed by the finish, giving the best balance against the specification. The justification names properties, cost, manufacture and a solution to the one drawback.

How this module is examined

Define and apply properties. State what each property means and link it to a design choice, not just the definition.
Classify confidently. Place a named material into the right family (hardwood or softwood, ferrous or non-ferrous, thermoplastic or thermoset) and give a use.
Explain why alloys are made. Strength, corrosion resistance or workability, with examples such as steel and brass.
Justify selection by trade-off. Weigh properties, cost, manufacture and impact, and explain the chosen material against the product's job.

Check your knowledge

Short questions across the module. Attempt them, then check the worked solutions.

State the difference between a mechanical and a physical property, giving one example of each. (2 marks)
Classify each of these as ferrous or non-ferrous: mild steel, aluminium, cast iron, copper. (2 marks)
State the key difference between a thermoplastic and a thermosetting plastic. (2 marks)
Give one reason an alloy such as steel is made rather than using pure iron. (1 mark)
A child's outdoor toy must be light, weatherproof and brightly coloured. Suggest a suitable material and justify it. (2 marks)

Sources & how we know this

Singapore-Cambridge GCE O-Level Design and Technology (Syllabus 7059) — Singapore Examinations and Assessment Board (2026)