Properties of Materials

Properties of materials

Different materials behave in different ways. They have different properties.

Solid materials

Solid materials can differ in one or more of the following ways:

• melting point
• strength in tension (when pulled)
• strength in compression (when pushed)
• stiffness
• hardness
• density

Plastics, rubbers and fibres

Many of the products that we use are made using plastics such as polythene and rubbers; and fibres such as cotton. The suitability of a material to a particular job depends on its properties.

• A washing-up bowl may be made from the plastic poly(ethene), commonly called polythene, because this material is waterproof and can be melted and reformed into the desired shape.
• A bicycle tyre is made from rubber because it needs to be flexible and tough.
• A pair of tights may be made from nylon fibres because these are flexible and elastic.

Choosing suitable materials

The table below shows some properties of a number of materials. Consider which materials would be suitable to make a pair of shoes.

Materials and their properties

cotton
/ leather
/ polythene
/ rubber
/ wood

flexible / yes / yes / yes / yes / no
hard / no / no / no / no / fairly
tough / not very / yes / yes / yes / yes
heavy / no / no / no / no / yes
attractive / yes / yes / yes / no / yes
durable / fairly / very / fairly / very / very

Suitable materials for making the uppers of shoes are cotton, leather and polythene. They are flexible, tough, light and attractive. Rubber is unsuitable as it is unattractive and wood is too heavy and inflexible.

Rubber and leather are both good materials for making the soles of shoes because they are flexible and durable ie hard-wearing. Cotton and polythene are flexible but not durable enough, and wood is durable but not flexible enough.

Effectiveness and durability

How well a product does the job it was designed for depends on the effectiveness and durability of the materials that were used to make it. Consider again the materials you would use to make a pair of shoes, but think about the materials that would be most durable and effective.

A pair of shoes made with leather uppers and a rubber sole would be most effective and durable:

• Leather is waterproof and flexible; it can also be dyed in a range of colours, and can be given a shiny, polished surface.
• Rubber is also waterproof and flexible; it is very hard-wearing, and will not slip easily when in contact with flooring materials.

The properties of these materials make them suitable for making this product. Shoes made with leather uppers and rubber soles can carry out their job effectively and are durable, which means they last a long time before wearing out.

1. Which of these is not a property of a material?

melting point
cost
density
2. Which of these is an important property of the material used to make a pair of tights?

flexibility
density
hardness
3. High strength in tension is a good property for a material used to make:

rope
bricks
window frames
4. The property of lasting a long time before wearing out is know as:

density
effectiveness
durability
5. Rubber is a good material for making wellington boots because it is:

hard
waterproof
stiff

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