Núria Moreno

TECHNOLOGY

UNIT 4: Materials

This is my presentation of the UNIT 4: Materials.

First of all I’m going to show you the contents:

1. Raw materials

2. Materials

2.1. Different types of materials

3. Manufactured goods

4. Properties of materials

4.1. Physical properties

4.1.1. Explanation (Physical properties)

4.2. Chemical properties

4.3. Ecological properties

4.1.3. Explanation (Ecological properties)

1. Raw materials:

They are substances that are extracted directly from natural objects.

They are classificated into three groups: 1. Raw materials from animal origin

(such as wool). 2. Raw materials from vegetable origin (for example cotton). 3.

Raw materials from mineral origin (like marble).

2. Materials:

They are processed raw materials that are ready for making any type of product.

There are two types of processes: 1. The physical process which consists in to

change the state of a substance, but the chemical composition is the same. 2. The

chemical process that consists in to transform a substance into a different one

with different characteristics. The chemical composition changes, too.

2.1. Different types of materials:

There are 6 types of materials: wood, metals, plastics, textiles, stone and

ceramics.

3. Manufactured goods:

They are products made by humans to help or satisfy their needs and improve

their standard of living.

4. Properties of materials:

There are three types: 1. Physical properties. 2. Chemical properties. 3.

Ecological properties.

4.1. Physical properties:

The physical properties are the ones which relate to how materials react to

external stimuli.

Here there’s a scheme with all the physical properties that we studied:

electrical properties (conductivity and insulation), thermal properties

(conductivity: conductors and insulator; expansion and contraction,

fusibility and welding), acoustic properties (conductivity and insulation),

magnetic properties (magnetism), optical properties (opaque, translucent

and transparent), mechanical properties (mechanical strength: tensile,

flexural, compressive, shear and torsional; elasticity and plasticity,

malleability and ductility, hardness and toughness and brittleness) and

other properties (density, porosity, permeability and impermeability).

4.1.1. Explanation (Physical properties):

Now I’m going to explain you all the physical properties:

Electrical properties: The materials that have electrical conductivity

are the ones that conduct electricity; and the materials that have

electrical insulation are the ones that don’t conduct it.

Thermal properties: The thermal conductivity is when a material

conducts heat and the insulation is when a material doesn’t conduct

heat. The expansion is when the temperature increases and the

material expands. The contraction is when the temperature decreases

and the material contracts. The fusibility is when a material changes

from solid to liquid when its temperature is increased. Welding is a

property that consists in join together pieces by using heat or

chemicals.

Acoustic properties: The acoustic conductivity is the capacity of

materials to transmit sound; and the acoustic insulator is when a

material doesn’t conduct sound well.

Magnetic properties: The magnetism is the property that has some

metals of attract other metallic materials.

Optical properties: The opaque materials doesn’t allow light pass

through them. The translucent materials allow light pass through them,

but the objects behind can’t be seen clearly. The transparent materials

allow light pass through them and the materials can be seen clearly.

Mechanical properties: The mechanical strength: The materials that

have tensile strength resist stretching. The materials that have

flexural strength resist bending or flexing (to curve something). The

materials that have torsional strength resist twisting (to turn

something). The materials that have compressive strength resist

crushing or compressing (to press something). The materials that have

shear strength resist sliding forces (forces de lliscament). Elasticity:

allows the material to return to its original form after a force that has

changed its shape is removed. Plasticity: allows to be permanently

deformed. Malleability: allows a material to be spread into sheets or

films. Materials with this property are malleable. Ductility: allows a

material to be deformed into filaments/wires. Materials with this

characteristic are ductile. Hardness: the materials that are hard are

difficult to scratch. Toughness: the materials that have this property

are difficult to break. Brittleness: the materials that have this

property are easy to break.

Other properties: Density: is the relationship between the mass and

the volume of an object. Porosity: there are materials that can absorb

or expel liquids or gases. Permeability: is the capacity of some

materials to don’t allow liquids to filter through them. The materials

that have this property are permeable. Impermeability: is the opposite,

they don’t allow liquids to filter through them. The materials that have

this property are impermeable or waterproof.

4.2. Chemical properties:

The chemical properties are the ones that when a material interacts with

other substances the chemical composition changes.

We only learnt one chemical property: Oxidation. It’s when a mineral reacts

with oxygen, the air or water. The brown thing that appears is the rust. To

prevent rusting we coat materials with paint, varnish, etc.

4.3. Ecological properties:

These are the properties that say how does the material impact on the

environment.

Here there’s a scheme with all the different properties: recyclable

materials, toxic materials, biodegradable materials, renewable raw

materials and non-renewable raw materials.

4.3.1. Explanation (Ecological properties)

Now I’m going to explain every property one by one as I did before

with the physical properties.

Recyclable materials: These can be reused. They help conserve natural

resources and avoid the accumulation of waste products.

Toxic materials: These are harmful to the environment.

Biodegradable materials: These materials are decomposed naturally

and don’t cause damage to the environment. They decompose on contact

with cold or hot water).

Renewable raw materials: These raw materials can be regenerated

naturally.

Non-renewable raw materials: These can’t be regenerated and are

going to be sold out (van a esgotar-se).

THE END