S3 Metals

Question 1

List 4 reasons for making alloys.

Answer 1

1) make metals harder and stronger
2) improve appearance of metals
3) make metals more resistant to corrosion
4) lower melting points of metals so that less electricity is needed to melt the metals

Question 2

Define alloy.

Answer 2

An alloy is a mixture of a metal with one or more fee other elements

Question 3

Why are metals used in the form of alloys?

Answer 3

Pure metals are too weak and soft because the layers of atoms can easily slide over one another. Alloys are stronger and harder because the atoms of the two elements have different sizes, and hence the layers of atoms cannot slide over one another easily, as the regular arrangement of atoms is DISRUPTED.

Question 4

What metals can react with cold water? What does it produce?

Answer 4

Potassium, sodium, calcium, magnesium, aluminum

It produces hydrogen and metal hydroxide.

Question 5

What metals can react with steam? What does it produce?

Answer 5

Magnesium, aluminum, zinc, iron and tin

It produces hydrogen and metal hydroxide.

Question 6

Why must less reactive metals react with steam instead of cold water?

Answer 6

Steam has a higher energy level that cold water. Less reactive metals need higher amount of energy to spur the reaction.

Question 7

What are 3 characteristics of more reactive metals?

Answer 7

1) can displace less reactive metals from their salts dissolved in water during precipitation
2) reaction produces more energy
3) faster reaction

Question 8

What happens when a piece of zinc metal is placed in copper(II) sulfate solution?

Answer 8

Reddish brown solid copper forms on zinc and blue solution becomes colorless (zinc sulfate)

Question 9

Describe the concept of metal compound’s heat stability.

Answer 9

The more reactive the metal, the more likely it is to form a compound. It has lesser charge and thus is harder to separate the compound. The compound is more stable and thus, it is less affected by heat.

Question 10

Define metal ores.

Answer 10

An ore is a type of rock that contains minerals with important elements including metals, which are generally oxides, sulfides and silicates.

Question 11

Which metals require electrolysis of molten metal ores to extract it?

Answer 11

Potassium, sodium, calcium, magnesium, aluminum

Question 12

Which metals require heating with reducing agent to extract it from the ore? Name the 3 reducing agents as well.

Answer 12

Zinc, iron, tin, lead, copper

Reducing agents: carbon, coke/hydrogen

Question 13

Which metals are found as metal in the ground?

Answer 13

Gold

Question 14

List 3 advantages of recycling metal.

Answer 14

1) conserve natural resources
2) reduce environmental problems related to extracting metals from their ores
3) saves cost of extracting metals from their ores

Question 15

Define rusting.

Answer 15

Rusting is a chemical process by which iron reacts with oxygen and water to form rust.

Question 16

What is the equation of rusting?

Answer 16

Iron + oxygen + water –> hydrated iron (III) oxide

Question 17

List the 5 ways to prevent rusting.

Answer 17

1) galvanising/blocks of zinc metal for ships
2) painting
3) tin plating
4) cover with oil or grease
5) making stainless steel

Question 18

List the advantages and disadvantages of painting.

Answer 18

A: prevents oxygen and water from coming into contact with the surface of iron
D: if the paint layer is broken, the iron will begin to rust and spread beneath the paint.

Question 19

What is galvanising?

Answer 19

Covering iron or steel with a thin layer of zinc. If the surface is damaged, zinc corrodes in place of iron as it is more reactive than iron. Zinc loses valence electrons more readily. (Sacrificial protection)

Question 20

List the advantages and disadvantages of tin-plating.

Answer 20

A: protects steel cans from rusting
D: when scratched, tin-plated iron surfaces rusts FASTER than if tin was not present as iron is more reactive than tin. It has a higher tendency to lose electrons than tin.

Question 21

List the advantages and disadvantages of covering iron with oil or grease (2/1)

Answer 21

1) prevents rusting
2) helps lubrication

1) protective film of oil/grease gathers dust and must be renewed

Question 22

What is stainless steel? List the advantages and disadvantages of stainless steel?

Answer 22

Stainless steel is an alloy of iron, carbon, nickel and chromium, which is used for utensils and medical instruments.
A: does not rust
D: expensive

Question 23

Why is aluminum corrosion resistant?

Answer 23

It is reactive. When placed in air, it immediately reacts with oxygen in the air to form a layer of aluminum oxide, preventing other reactions from occurring.

Question 24

Why can metal A used to protect metal B from corroding?

Answer 24

Metal A is more reactive than metal B, and oxidises more readily than metal B. Metal A thus corrodes in place of metal B.

Question 25

What is steel?

Answer 25

Iron extracted from blast furnace is made into steel, and alloy of iron with carbon and/or other metals. Adding different amount of carbon or metals produce different types of steel.

Question 26

What is the use and special properties of mild steel?

Answer 26

Use: car bodies and machinery
SP: hard, strong, malleable

Question 27

What is the use and special properties of high carbon steel?

Answer 27

Use: cutting and boring tools like hammers
SP: strong but brittle

Question 28

What is the use and special properties of manganese steel?

Answer 28

Use: springs and drills
SP: hard and strong

Question 29

List 3 disadvantages of recycling metals.

Answer 29

1) costly: transporting, sorting and recycling
2) takes time and effort to adapt recycling as a lifestyle, which is not immediately efficient
3) pollution to environment: harmful gases are produced when melting car batteries

Question 30

Which metal compounds are unaffected by heat?

Answer 30

Potassium and sodium

Question 31

Which metal compounds decompose into carbon dioxide and metal oxide upon heating?

Answer 31

Calcium, magnesium, zinc, iron, lead, copper

Question 32

Which metal compounds decompose into pure metal and carbon dioxide on heating?

Answer 32

Silver

Question 33

Describe the process in the blast furnace. (7)

Answer 33

1) haematite, coke and limestone is added. Carbon in coke burns to produce carbon dioxide and a lot of heat.
2) as carbon dioxide rises, it reacts with more coke to form carbon monoxide.
3) carbon monoxide reduces iron(III) oxide in haematite into molten iron, which runs to the bottom of the furnace.
4) limestone is decomposed by heat to form carbon dioxide and calcium oxide.
5) calcium oxide reacts with silicone dioxide and other impurities in haematite to form molten slag (calcium sillicate)
6) hot waste gases escape through the top of the furnace while molten slag floats above molten iron.
7) slag and iron and tapped off separately.