Different materials

Different materials have different properties, but they may also have some properties in common. Data is used to compare materials and to select the most suitable material for a product.

This table summarises some of the typical properties of glass and clay ceramics, metals and polymers:

Glass ceramicsClay ceramicsMetalsPolymers
AppearanceTransparentOpaqueShinyTransparent or opaque
Melting pointHighHighHighVariable
Malleable or brittleBrittleBrittleMalleableBoth
Electrical conductivityPoorPoorGoodPoor
Ability to conduct heatPoorPoorGoodPoor

Ceramics

Brick wall
Brick is strong in compression - it resists being squashed

Clay ceramics include brick, china and porcelain. Clay ceramics are opaque.

Ceramics are:

  • hard
  • strong in compression so they don’t give way when squeezed
  • weak in tension and break easily if stretched
  • brittle which means that they snap rather than change shape when stressed
Broken glass window
Glass shatters when it is hit or dropped

Glass is a transparent ceramic material.

Metals

Metals are:

  • malleable so they can be bent into shape without shattering
  • ductile so they can be made into wires without shattering
  • good conductors of electricity and heat
  • strong in tension and compression
  • stiff so they keep their shape when forces act on them

The density of metals varies. An object made of a dense metal is heavier than one made of a less dense metal.

Polymers

Polymers are:

  • poor conductors of electricity and heat
  • durable (last a long time)
  • low in density, meaning that objects made from polymers tend to be lighter than those made from metals

Their other properties, such as melting point, vary depending upon the type of polymer.

Polymers can be transparent or opaque. They are often flexible, but some are brittle. Many polymers are not hard and can dent or scratch easily.

The softening temperature depends on the type of polymer. Some polymers soften when heated but others, once moulded, no longer soften.