1. AQA GCSE 3 Metals and alloys Design and Technology 8552 Unit 3
Materials and their working properties 3

2. Objectives
Know the primary sources of materials for producing metals and alloys
Be able to recognise and characterise different types of metals and alloys
Understand how the physical and working properties of a range of metals and alloys affect their performance

3. Metal Metals have been essential in the development of civilisation
The word ‘metal’ comes from the ancient Greek word ‘metallon’ which means to mine, excavate or extract from the ground
Prehistoric man used metals to make tools and weapons
Which common metals would you find in a domestic kitchen?

4. Ore The Earth’s crust contains many types of rock
Metallic minerals are found naturally in rock or ore
Ore is obtained by mining and the metals within it are extracted
The method used for extraction depends on the metal’s reactivity with air, water or acids
The more reactive the metal, the more expensive it is to extract

5. Finding metal
Some naturally occurring metals are found as lumps in the rock and don’t require a chemical extraction
Why is gold expensive in comparison to aluminium?

6. Extraction processes Some metals exist as oxides
Metals such as copper, iron and zinc are oxides. These are heated with carbon to extract the metal
Electrolysis is used to extract metals such as aluminium
Are metals a renewable resource?
How can man reduce the speed at which we will run out of natural resources?

7. Iron ore
Iron can be extracted from iron ore by using a blast furnace and the process of smelting
Smelting extracts common industrial metals such as iron
The extreme heat draws off the metals in a liquid state called ‘hot metal’
The impurities are removed and the iron mixed or ‘alloyed’ with a small amount of carbon to create steel
The amount of added carbon affects the strength of the steel

8. Ferrous metals Ferrous metals contain iron and may rust
Iron and steel can corrode – this is known as rust
Rust is a compound called iron oxide and is formed when iron and oxygen react in the presence of moisture or water
Most ferrous metals are magnetic
Name two types of protective layer that could be added to metal to help prevent rust

9. Ductility and malleability
Ductile metals
Will stretch without being damaged
Can be drawn or stretched out into long wires
Copper is highly ductile and can be drawn into long, thin wires
Malleable metals
Can be hammered into a shape without breaking
Can be rolled or pressed into sheets
Will deform under compression

10. Hard or tough? Hardness – a material’s ability to withstand abrasion
A very hard metal is likely to crack or shatter upon impact or force. Cast iron would be described as hard and brittle
Toughness – metal requires strength and ductility
This is how well a metal can absorb energy and resist fracturing without deforming

11. Tensile strength
Tensile strength is the amount of tensile stress (stretching) a material can withstand before breaking or failing
Testing for tensile strength is crucial in industry
Suggest two uses for metals with high tensile strength
Why is destructive testing so important?

12. Hard as nails Steel is a ferrous metal available in different forms
Steel has a high resistance to corrosion, staining and friction which makes it suitable for a wide range of uses
These elements give steel its characteristic properties of hardness and toughness
High speed steel is formed by alloying elements of carbon, tungsten, vanadium, cobalt, chromium or molybdenum
Name three everyday applications of stainless steel

13. Material selection
Ferrous metals have varying properties making them suitable for different uses
Low carbon steel is tough, ductile and easily welded
High carbon steel is very hard wearing, but less ductile or malleable
Cast iron is hard and easily cast into shapes, but brittle
Suggest two items made from each of these metals?

14. Non-ferrous properties
Non-ferrous metals don’t contain iron
They are often more expensive than ferrous metals owing to their desirable properties which include:
Lightweight
Good conductivity
Ductile and malleable
Resistant to corrosion
The process of galvanising adds a protective coat of zinc to iron and steel to help prevent rusting

15. Electrical conductivity
Conductivity is how easily an electrical current can flow through a metal
As copper is such an efficient conductor, it’s most common use is in electrical cabling

16. Thermal conductivity
Thermal conductivity measures the ability of a metal to conduct heat
Copper is also an excellent conductor of heat and is commonly used in air conditioning, water tanks, saucepan bases and water heaters
In what environment would it be more appropriate to use steel than copper?

17. Non-ferrous metals
Aluminium, copper, tin and zinc are all non-ferrous metals
List a selection of household items that may be made from non-ferrous metals
In what way do non-ferrous metals differ from ferrous metals?

18. Tin Tin is commonly associated with a ‘tin can’
In fact, the can is steel, with a thin coating of tin, ‘tin plating’, which helps preserve the contents
Tin is soft, ductile and malleable
Alloys of tin include pewter, copper, bronze and soft solder
What other non-ferrous metal is associated with the production of cans?

19. Alloys
Metals are rarely used in their pure form. Alloys are made by combining two or more elements
This helps improve the working properties and appearance
Brass and steel are common alloys
Stainless steel is made by combining iron, with a small amount of carbon and chromium
This protects the alloy from oxygen – what will this help prevent?
What are the advantages of creating alloys?

20. Worksheet
Complete Tasks 1 and 2 on your worksheet

21. Uses of metals
Given the various properties of metals, list as many metals as you can that are used to make this bicycle

22. Uses of metals Answers
A vast range of metals may be used to create a single product
Twisted strands of steel in the brake cables, aluminium and steel in the brake handle
Frame could be low carbon steel, aluminium alloy
Steel springs
Aluminium mud guards
Aluminium or stainless steel shopping basket
Steel or aluminium spokes
Chain made of carbon steel
Steel wire in the tyres, zinc in the manufacture of rubber
High speed steel in ball bearings, pedals, wheel hubs, headstocks, cranks
Fused or welded joints are usually brass (a copper / zinc alloy)
Aluminium alloy
in the pedals

23. Worksheet
Complete Task 3 of the worksheet

24. Everything but tin? Tin probably didn’t feature in your bicycle list
Working with recycled cans is a technique called Kapoaka
Used in Madagascar by small scale workshops, crafters make decorative objects and toys for sale
It has created sustainable employment and helps the poorest in Africa attain a living from the profits

25. Oxidisation
Non ferrous metals such as copper and bronze, don’t rust, but may oxidise
Oxidising can be caused by corrosion or weather exposure over a period of time
A thin layer of tarnish that appears on the surface of the metal is known as a patina
A natural patina occurring on copper is called Verdigris
The green hue can be manufactured by adding acetic acid to copper and is often used in architecture for aesthetic purposes

26. Plenary What are metals commonly extracted from?
Name three ferrous metals
Which metal would you select for high conductivity?
Explain the term ‘alloy’
Describe the difference between hard and tough
How can you protect metal from oxidisation?
Justify one metal used to manufacture cutting tools