4.2 Properties of Materials

Physical Properties

Definitions (4.2.1)

Density is the amount of matter in a particular unit of space.

Electrical resistivity is the measure of a material’s ability to conduct electricity. For example, a material with high resistivity will not conduct electricity well.

Thermal conductivity is the measure of the rate at which heat can pass through a material with a temperature difference across the material given.

Thermal expansion is the change of the dimensions of a material is relation to its temperature.

Hardness is the resistance of a material when a force is applied.

Design Context (4.2.2)

It is important for the density of a material to be considered when transporting the material, or when conversions are being made, e.g. from a wax model to the final product in silver.

Electrical resistivity
The conductivity or insulation of a material being used can be key for the use and safety of the product. For example, the glass of a light bulb needs to be an insulator, otherwise the electricity flowing through the metallic filament of the light may be transferred to the glass.

Thermal conductivity
Thermal conductivity needs to be taken into account as a safety measure. For example, if the casing of a heater or toaster has extremely high thermal conductivity, it may cause a safety hazard to touch. It is also important for objects that need to be heated. For instance, the heating element of a kettle needs to have high thermal conductivity in order to heat the water.
You can click here for an informative video on thermal conductivity.

Thermal expansion
Understanding thermal expansion is key when two different materials are joined together. Joined materials may have varying levels of thermal expansion, causing splitting or damage to the object if thermal expansion is not considered.

The hardness of a material should be linked to the level and types of use of the material. For example, a soft wood for floorboards is unsuitable, due to the repeated pressure on the wood, causing dents and scratches.

Mechanical Properties

Definitions & Design Context

Tensile Strength
The ability of a material to withstand pulling forces. The tensile
strength is important in selecting materials for ropes and cables, for
example, for an elevator.

The resistance of an elastic body to deflection by an applied force.
Stiffness is important when maintaining shape is crucial to performance,
for example, an aircraft wing.

The ability of a material to resist the propagation of cracks. Toughness
is important where abrasion and cutting may take place.

The ability of a material to be drawn or extruded into a wire or other
extended shape. Ductility is important when metals are extruded (not to be
confused with malleability, the ability to be shaped plastically).

This table, taken from http://departments.sis.edu.hk/dt/dtsis/index2.htm, is a clear way of showing the physical and mechanical properties of various materials:

Aesthetic Characteristics


Taste is the flavour which a subrstance gives.

Smell is the aroma which a substance gives.

Appearance is the aesthetic aspects of a substance.

Texture is how the substance feels to touch and also how the substance

Colour is the pigmentation of a substance which can be formed through
light or chemicals.

Design Context

The appeal of taste refers to food products.

Smell, whilst it may relate to food, also relates to different materials. For example, the smell of sandalwood on a wooden object can be considered an appealing quality for the object.

The physical appearance of an object appeals to a person’s sense of sight. It can be an immediate attractive point or deterrent. In many cases appearance immediately determines a person’s interest in a product.

The texture of an object adds interest to the piece, once a person has already been drawn to it. It can also contribute to the comfort of the piece, for example a soft lounge.

Colour, already encompassed in Appearance, plays a major role in attracting a person to the piece. It is also to be considered in relation to other objects in a space, for instance a particular colour scheme for a bedroom.

Here are three images of the same bedroom, demonstrating the role colour plays in altering a space:


These images were taken from www.taubmans.com.au

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