C10. Metals

Question 1

List the physical properties of metals.

Answer 1

• Generally solids at room temperature
• Ductile
• Malleable (can be beaten into a different shape with a hammer)
• Conductor of electricity and heat
• High densities
• High boiling and melting points
• Hard
• Shiny
• Strong
• Sonorous

Question 2

List the physical properties of most non-metals.

Answer 2

• Low densities
• Does not conduct heat
• Does not conduct electricity
• Not malleable
• Dull surface
• Not ductile
• Not sonorous

Question 3

List the chemical properties of metals.

Answer 3

• Many metals react to give off hydrogen gas
• When they react, metals form positive ions by losing electrons
• Many metals are basic.

Question 4

List the chemical properties of non-metals.

Answer 4

• Non-metal are acidic.
• Most do not react with acids
• When they react with metals, non-metals form negative ions by gaining electrons.

Question 5

What is an ‘alloy’?

Answer 5

A mixture of two or more metals, or one or more metal with a non-metal.

Question 6

What are uses of alloys?

Answer 6

Improve strength, hardness or resistance to corrosion.

Question 7

Name some examples of alloys.

Answer 7

Brass = copper + zinc
Bronze = copper + tin
Stainless steel = iron, nickel + chromium

Question 8

List the reactivity series in order of most reactive to least reactive.

Answer 8

Lithium - Li
Potassium - K
Calcium - Ca
Sodium - Na
Magnesium - Mg
Aluminium - Al
CARBON - C
Zinc - Zn
Iron - Fe
Nickel - Ni
Tin - Sn
Lead - Pb
HYDROGEN - H
Copper - Cu
Mercury - Hg
Silver - Ag
Gold - Au
Platinum - Pt

Question 9

List the metals in the reactivity series that exist as native metals.

Answer 9

• Silver
• Gold
• Platinum

Question 10

What is an ‘ore’?

Answer 10

A rock containing enough of a metal compound for it to be worth extracting the metal from the rock.

Question 11

What is ‘bauxite’?

Answer 11

Bauxite contains aluminium oxide

Question 12

What is ‘hematite’?

Answer 12

Iron oxide

Question 13

How do we extract metals that are more reactive than than carbon?

Answer 13

Electrolysis

Question 14

Describe the use of carbon in the extraction of some metals.

Answer 14

Reduction with carbon.
- Used for oxides of metals less reactive than carbon - the carbon displaces the metal, stealing the oxygen to form carbon dioxide and leaving the metal. Carbon is used because it is cheap and plentiful.

Question 15

Describe how iron is extracted from its ore in the blast furnace and the raw materials needed.

Answer 15

Raw materials: hematite, coke (carbon but with impurities), limestone and air.

• A strong current of air is blown in at the bottom of the furnace.
• Temp: between 250C at the top and 1500C at the bottom.
• Main reducing agent: carbon monoxide.

Question 16

What are the essential reactions and the steps taken in extracting the iron?

Answer 16

• At the bottom of the furnace, the coke burns with hot air to form carbon dioxide (exothermic):
  C(s) + O2(g) -> CO2(g)
• The carbon dioxide reacts with the coke to form carbon monoxide:
  CO2(g) + C(s) -> 2CO(g)
• The carbon monoxide reduces the iron(III) oxide to iron:
  Fe2O3(s) + 3CO(g) -> 2Fe(l) + 3CO2(g)
• In hotter parts of the furnace, carbon reduces iron(III) oxide directly:
  Fe2O3(s) + 3C(g) -> 2Fe(l) + 3CO(g)

Question 17

Why is limestone needed in the extraction of iron?

Answer 17

Hematite contains sand (silicon(IV) oxide) as a major impurity. The limestone helps remove the impurity.

Question 18

What are the chemical reactions needed for the removal of impurities in hematite by limestone?

Answer 18

• The heat decomposes the limestone:
  CaCO3(s) -> CaO(s) + CO2(g)
• The calcium oxide reacts with the silicon(IV) oxide to form a slag of calcium silicate:
  CaO(s) + SiO2(s) -> CaSiO3(l)

Question 19

Why is aluminium widely used in aircraft?

Answer 19

It is lightweight - it has a low density - and also quite strong.

Question 20

What are the alloys made from aluminium that is used for aircraft?

Answer 20

Aluminium alloys contain 90% aluminium and smaller amounts of zinc and copper.

Question 21

What is zinc used for?

Answer 21

Galvanise (coat) iron or mild steel to prevent rusting.

Question 22

Why is aluminium used in food containers?

Answer 22

There is an unreactive oxide layer on its surface which does not flake off - does not react with acids that are present in many foods.
Resistant to corrosion.