Why do we choose different materials to make different things? Theory and example (chair)

1. Why do we use
different materials
to make
different things?
Javier Gómez Calzada
1ºESO, 3ºESO

2. 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

3. 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)

4. 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

5. Which materials would you use for
these objects? Why?
• Chair
• Pan
• Book
• Wire
• Jacket
Use the words
Write a sentence using each of 22 properties in the
previous slide.
Be sure you know its translation to Spanish.

6. 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