Properties of materials

When selecting a material for a particular product the first question you need to ask is: what materials are suitable for the product? A material which melts at a low temperature, for example, would not be suitable for making a saucepan. Similarly, a material which absorbs water, would be unsuitable for making waterproof boots. It's essential therefore, to choose a material with the appropriate properties. In the case of the boots , the material must be waterproof, have good heat insulating properties, and flexible. In the case of the saucepan body, the material must be capable of whitstanding a high temperature, be a good conductor of heat, be light in weight and so on.

We use different materials in differents ways depending on their properties. Physical properties are related to how materials react to external stimuli, for example electricity, heat or forces applied.

Electrical conductivity or insulation: some materials conduct or don't conduct electricity. Metals are good conductors and plastics are good insulators.
Thermal conductivity or insulation: some materials conduct or don't conduct heat. Metals are good conductors and plastics are good insulators.
Expansion and contraction: when the temperature increases the material expands and when the temperature decreases the material contracts. Metals are especially sensitive to expansion and contraction.
Fusibility: some materials change from solid to liquid when their temperature is increasing, e.g. metals, some plastics and glass.
Welding: some materials can be used to weld to pieces of the same or different materials together, e.g. metals
Acoustic conductivity or insulation: some materials transmit or don't transmit the sound. Metals are good conductors and plastics, glass, fibre and cork are good insulators.
Magnetism: some metals, like iron, attract other metallics materials, e.g. a magnet
Optical properties: opaque is when objects can't be seen it through them, e.g. wood and metals; translucent is when objects allow ligth to pass through them, e.g. some glass, tissue papers and plastics; transparent is when objects can clearly be seen through them, e.g. glass and some plastics.
Strength: is a measure of how good a material is at resisting being misshapen, or deformed, when acted upon by a force. There are several types of strength: tensile strength, compressive strenght, flexural strenght, torsional strength and torsional strength.
Elasticity and plasticity: elasticity allows a material to return to a original form after a force that has changed its shape is removed and plasticity allows it to be permanently deformed.
Malleability allows a material to be spread into sheets or films.
Ductility: allows a material to be formed into filaments or wires.
Hardness: is a measure of its ability to withstand being scratched, cut or dented.
Toughness: is a measure of how much energy is required to break a material when it's hitten by something.
Brittleness: a brittle material is one which fractures with little or no deformation. A brittle material under tension can break suddenly and withou warning.
Density: is the relationship between the mass of an object and its volume
Porosity: is the capacity of some materials to absorb or release liquids or gases. This property is related to density, if a material is more porous, it is less dense.
Permeability: some materials allow water or other liquids to filter through them.
Impermeability: some materials don't allow water or other liquids to filter through them.

SPANISH TERMS

Electrical conductivity or insulation: Conductividad eléctrica o Aislamiento
Thermal conductivity or insulation: Conductividad Térmica o Aislamiento
Expansion and contraction: Contracción y Expansión
Fusibility: Fusibilidad
Welding: Soldadura
Acoustic conductivity or insulation: Conductividad Acústica o Aislamiento
Magnetism: Magnetismo
Opaque: opaco
Translucent: translúcido
Transparent: transparente
Strength: Resistencia
Elasticity and plasticity: Plasticidad y Elasticidad
Malleability: Maleabillidad
Ductility: Ductilidad
Hardness: Dureza
Toughness: Tenacidad
Brittleness: Fragilidad
Density: Densidad
Porosity: Porosidad
Permeability: Permeabilidad
Impermeability: Impermeabilidad