Materials. Introduction

Posted on December  14th, 2009 by Technology Department 

Millions

new materials

 Millions of years ago, man used to manage simples materials, such as wood, to make unsophisticated tools or constructions Nowadays, man has invented new materials which can be used in many different situations, even in our own bodies ( See illustration on the right where old tooth are replaced by implants.  

Materials and Components

  1. Choosing the correct material for any particular task is essential for a manufacturing activity. Materials can be natural or artificial. Natural resources are split into 3 categories. 1. Animal 2. Vegetable 3. Mineral  

Artificial Materials: ARE THOSE WHICH HAVE BEEN MADE BY MAN

TYPES OF MATERIALS

1º Wood: Divided into two major classifications: Hardwoods and Softwoods. 2º Metals. There are two significant groups of metals: Ferrous metals, which contain iron and non-ferrous metals, which do not contain iron. Examples of Non-ferrous metals are: Aluminium, Copper, Gold, Silver ...  

Materials Properties of Materials

Properties of materials can be divided into physical, chemical and ecological

Physical Properties

Electrical Conductivity is  when electricity can run though the material.  Examples: Steel is a good conductor Wood isn't a good conductor

Optical properties

How materials behave when light touches them. They can be classified into: a) Opaque: No light travels through them. e.g wood b) Transparent: All light travels through them and you can see what's behind the materials. e.g glass in a  window c) Translucent: All light can travel through them but you cannot see what's behind them e.g frosted glass

See examples on page 75  

SAUCEPANWhat is a thermal conductor and what is an insulator ?

It is the ability of the material to conduct heat. e.g. In a saucepan there is a metal body for thermal conductivity and plastic handles for thermal insulation. Thermal Insulation = It is a bad thermal conductor  

Thermal properties

Dilation: When material expands ( gets bigger ) due to heat rail gap Contraction: When material gets smaller due to heat.

 To think about: Why are rails separated by a gap?

Thermal properties

Fusibility is the ability of a material to change into a liquid when heated to its melting point. Examples of melting points: Iron’s melting point...........1535 ºC 

Copper’s melting point..........1083 ºC

Sound Properties

The ability of materials to conduct sound. To think about. Can you speak on the moon. I mean, can your partner hear what you say?. Write some examples of good and bad conductors

Oxidation.

The change that occurs to most metals when in contact with air or/and water

 

Ecological Properties

  • Recyclable. Materials that can be reused
  • Toxic. Materials which are harmful to the environment
  • Biodegradable. Materials that decompose naturally with time. Examples:

    An apple takes about 20 days to decompose,  plastic takes about 100 years  and glass takes about 400 years

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    Posted on 2009