Why do we usedifferent materials to make different things? Javier Gómez Calzada 1ºESO, 3ºESO
Why do we use different materials to make different things?Different materials have different characteristics:• Properties (weight, hardness, elasticity, …)• Price• Appearance• Availability• Easiness/difficulty of use• Effects on health• Effects on environment
Most important types of materials Wood (eg oak, MDF) Metals (eg steel, copper) Plastic (eg vinyl, PVC) Fabric (eg cotton, polyester) Ceramic (eg clay, porcelain)
Some important properties• Colour, shininess• Weight, density• Strength, toughness, hardness, brittleness• Feel, texture• Resistance to heat, resistance to corrosion• Conductivity/insulation (electrical or heat)• Flexibility• Ability to see through: opaque, translucent, transparent• Elasticity, plasticity• Malleability• Ductility
Which materials would you use for these objects? Why?• Chair• Pan• Book• Wire• Jacket Use the wordsWrite a sentence using each of 22 properties in the previous slide.Be sure you know its translation to Spanish.
A CHAIR could be made of wood because• The wood has a good appearance• It is strong, tough• It can be environmentally friendly (it depends on the type of wood)• It is not usually expensive (it depends on the type of wood) But if we want an outdoor CHAIR, maybe it is better to make it of plastic: • The plastic has a better resistance to humidity, so it will last longer • It has some flexibility, so the chair can be more confortable • It is cheaper than wood • It is not as heavy as wood