jueves, 3 de febrero de 2011

Properties of Materials

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

1-Physical Properties
Electrical Conductivity
: When electricity can run though the material.
Steel is a good conductor
Wood isn't a good conductor

Optical properties:
How materials behave when light touches them
Them 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 of window
c) Translucent: All light can travel through them but you cannot see what's behind them e.g frosted glass

Thermal Conductivity

¿ What is conductor and what is insulator ?

Plastic handles are ...
Metal Body is ...

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

Dilation and contraction and Fusibility

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

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

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?
Write some examples of good and bad conductors

2 Chemical Properties

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

3 Ecological Properties

Recyclable. Materials that can be reused
Toxic. Materials which are harmful to the environment
Biodegradable. Materials that decompose naturally with time. eg
An apple take about 20 days to decompose
Plastic takes about 100 years
Glass takes about 400 years


Exercises 1: Use as many words as you need to describe the following materials:

Properties: Strong, light, weak, heavy, low density, translucent, electrical conductor, magnetic

a) Wood b) Plastic c) Fabric d) Iron e ) Glass f ) Cork g) wool h) Aluminium

Exercise 2: Copy into your notebook the properties of transparent, opaque, waterproof, hard, strong and conductor.

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