Properties of materials

Why are saucepans made of metal with plastic handles? Because designers choose materials for their properties.

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Physical properties

Density: how much mass is packed into a certain volume. Density = mass ÷ volume.
Electrical conductivity: how well a material lets electricity pass through it. Metals are good conductors; most polymers and woods are insulators.
Thermal conductivity: how well a material lets heat pass through it. Metals conduct heat well, which is why pans are metal.
Absorbency: how well a material soaks up liquid, such as a cotton towel.

Working (mechanical) properties

These describe how a material reacts to forces:
PropertyMeaningExample
StrengthCan withstand a force without breakingSteel cables on a bridge
HardnessResists scratching, wear and dentingSteel drill bits
ToughnessAbsorbs impacts without breaking or crackingPolypropylene chair seats
BrittlenessBreaks or shatters easily without bendingGlass, cast iron
ElasticityReturns to its original shape after being stretched or bentA rubber band
PlasticityChanges shape permanently without breakingModelling clay
MalleabilityCan be hammered, pressed or rolled into shape without crackingAluminium, gold
DuctilityCan be stretched into a thin wireCopper

Choosing materials

Designers match properties to the job. A saucepan base needs good thermal conductivity; its handle needs to be a good thermal insulator.
Tough is the opposite of brittle. Hard is not the same as tough: glass is hard but brittle.
Cost, availability, how easy it is to work and its effect on the environment also matter.
Worked example

A block of metal has a mass of 270 g and a volume of 100 cm³. What is its density?

  1. Density = mass ÷ volume.
  2. 270 ÷ 100 = 2.7.
  3. The units are g/cm³.

Answer: 2.7 g/cm³ (this is the density of aluminium).

Key idea

Physical properties include density, conductivity and absorbency. Working properties include strength, hardness, toughness, elasticity, plasticity, malleability and ductility. Tough is the opposite of brittle.

Key words
Density
Density = mass ÷ volume, for example in g/cm³.
Hardness
The ability to resist scratching, wear and denting.
Toughness
The ability to absorb impacts without breaking or cracking.
Elasticity
The ability to return to the original shape after being stretched or bent.
Plasticity
The ability to change shape permanently without breaking.
Malleability
The ability to be hammered, pressed or rolled into shape without cracking.

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Extra practice

2 more questions

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  1. Which material is tough?

    1. Glass, which shatters
    2. Chalk
    3. Biscuit
    4. Polypropylene, which can be dropped without breaking
    Show the answer

    Answer: Polypropylene, which can be dropped without breaking

    Tough materials absorb impacts.

  2. Which property lets a material be drawn into thin wire?

    1. Malleability
    2. Ductility
    3. Brittleness
    4. Hardness
    Show the answer

    Answer: Ductility

    Ductile materials stretch into wire.

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Last updated 2 October 2026. Spotted a mistake? Tell us and we will fix it.

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