Extraction and Uses of Metals

Question 1

Sources of Metals

Answer 1

• Metals are found in the Earth’s crust as ores — rocks containing enough metal to be worth extracting.
• Most metals are combined as oxides and extracted by reduction (removing oxygen) using electrolysis, a blast furnace, or a more reactive material.
• Common ores: haematite (iron) and bauxite (aluminium). - Unreactive metals like gold and platinum are found as pure elements due to their stability.

Question 2

How are gold and silver extracted?

Answer 2

They aren’t, they are found as pure elements

Question 3

How are elements below carbon in the reactivity series extracted?

Answer 3

• Extracted by heating with a reducing agent such as carbon or carbon monoxide in a blast furnace
• A cheap process as carbon is cheap and can also be a source of heat

Question 4

How are elements higher than aluminum in the reactivity series extracted?

Answer 4

• Extracted by electrolysis of the molten chloride or oxide
• Large amounts of electricity are required, which makes this an expensive process

Question 5

Uses of Aluminium

Answer 5

• Aircraft bodies: High strength-to-weight ratio (low density)
• Saucepans: Very good conductor of heat and unreactive
• Overhead electrical cables: Very good conductor of electricity
• Food cans: Non-toxic, resistant to corrosion and resistant to acidic foodstuffs

Question 6

Uses of Copper

Answer 6

• Electrical wiring: Very good conductor of electricity and ductile
• Saucepans: Very good conductor of heat, unreactive, malleable
• Water pipes: Unreactive (does not react with water), non-toxic and malleable

Question 7

Uses of Iron

Answer 7

• Building material: Good strength, malleable and ductile, relatively inexpensive
• Catalyst: Variable oxidation state, increases the rate of reaction without being used up

Question 8

Uses of Mild Steel

Answer 8

0.25% C (Car body panels and wiring): Soft and malleable

Question 9

Uses of High Carbon Steel

Answer 9

0.5–1.4% C (Tools, e.g. chisels): Hard

Question 10

Uses of Stainless Steel

Answer 10

20% Cr and 10% Ni (Cutlery, sinks and chemical plants): Strong and resistant to corrosion

Question 11

What is an alloy?

Answer 11

• An alloy is a mixture of two or more metals or metal with a non-metal such as carbon
• Steel is made from iron and carbon

Question 12

Properties of Alloys that make them useful

Answer 12

• They can be stronger and harder
• They are resistance to corrosion or extreme temperatures

Question 13

Why are alloys harder than pure metals?

Answer 13

• Alloys contain atoms of different sizes
• This distorts the regular arrangements of atoms
• So it is more difficult for the layers of atoms to slide over each other