Metals

Question 1

Name the 6 physical properties of metals

Answer 1

1. Metals are ductile (able to be stretched into wires without losing toughness)
2. Metals are malleable (able to be bent into different shapes without breaking)
3. Metals are good conductors of electricity and heat
4. Metals have high melting and boiling points and generally are solids at room temperature.
5. Metals have high density
6. Metals are generally strong and shiny

Question 2

Metals have high melting points. Name one metal that is an exception to this rule.

Answer 2

Mercury has a low melting point (~39°C) and exists as a liquid at room temperature.

Question 3

Metals have high density. Which group of metals are an exception to this rule?

Answer 3

Group I metals such as lithium, sodium and potassium have low densities and float on water.

Question 4

Why are alloys stronger and harder than pure metals?

Answer 4

• Pure metals are soft as the layers of metal atoms are in an orderly arrangement and would slide over one another easily when an external force is applied to them
• In alloys, since the atoms have different sizes, the orderly arrangement of the metal atoms would be disrupted, making it tougher to slide over as easily. Hence, alloys are much stronger and harder.

Question 5

What are alloys?

Answer 5

An alloy is a mixture of a metal with one or few other metal or non-metal elements.

Question 6

Name 4 alloys and their respective components.

Answer 6

1. Steel (iron, carbon)
2. Stainless steel (iron, carbon, nickel)
3. Brass (copper, zinc)
4. Bronze (copper, tin)

Question 7

Give the initial of each metal in the reactivity series, from most reactive to least reactive.

Answer 7

PSCMACZITLHCMSG

Question 8

What is the method of extraction for PSCMA?

Answer 8

Compound broken down through electrolysis

Question 9

Method of extraction for ZITL?

Answer 9

Compound broken down by reduction with carbon

Question 10

Method of extraction for CMSG?

Answer 10

Compound broken down by thermal decomposition

Question 11

Describe the reaction between PSC and water.

Answer 11

Reacts readily with cold water and explosively with steam

Question 12

Describe the reaction between MACZI and water

Answer 12

Either reacts slowly or doesn’t react at all with cold water. All of them reacts with steam.

Take note that aluminium is covered by a thin layer of aluminium oxide and can only react with steam if the oxide layer is removed.

Question 13

Describe the reaction between TLCMSG and water

Answer 13

Does not react with cold water or steam

Question 14

Describe the reaction between PSCMAZITL and acid

Answer 14

All reacts with acid, ranging from vigorously to moderately to slowly

Question 15

Describe the reaction between CMSG and acid.

Answer 15

Does not react with acid

Question 16

In the periodic table, reactivity of metals increases going _____ the group and from ________________.

Answer 16

down; right to left

Question 17

Why does metal reactivity increase going down the group?

Answer 17

Going down the group, the metal has more valence shells, allowing it to lose its valence electrons more readily to form positive ions, hence it is more reactive.

Question 18

Metal + H2O (l) ——> ?

Answer 18

Metal hydroxide + H2

Question 19

Metal + H2O (g) ——> ?

Answer 19

Metal oxide + H2

Question 20

Metal + Acid ——> ?

Answer 20

Salt + H2

Question 21

What is a displacement reaction and why can it occur?

Answer 21

• A displacement reaction is when a more reactive metal displaces a less reactive metal from its solution or oxide
• It can happen because the more reactive metal is able to lose its electrons more readily to form cations

Question 22

When a metal carbonate undergoes decomposition upon being heated strongly, what are the products?

Answer 22

Metal oxide and CO2

Question 23

Describe and account for the trend between reactivity of a metal and ease of decomposition of its carbonate.

Answer 23

The more reactive a metal is, the ease of decomposition of its carbonate decreases as the carbonate has higher thermal stability

Question 24

CuO + H2 ——> ?

Answer 24

Cu + H2O

Question 25

Apart from a more reactive metal, oxides of less reactive metals can also be reduced by _______ and ________.

Answer 25

Carbon; hydrogen

Question 26

Rusting is the corrosion of iron and steel. State the equation of rusting.

Answer 26

Fe (s) + 3O2 (g) + 2xH2O(I) ——> 2Fe2O3.xH2O (s)

Note: x indicates the amount of water in rust varies

Question 27

What speeds up rusting? What can you conclude?

Answer 27

1. Presence of sodium chloride
2. Presence of acidic substances
   Iron objects near the sea/near industrial areas/in contact with seawater rust more rapidly

Question 28

Name the 3 ways to prevent rusting

Answer 28

1. Using a protective layer like paint, plastic or electroplating
2. Using a sacrificial metal (Protect iron or steel with a more reactive metal)
3. Using stainless steel (Stainless steel contains chromium so hard layer of chromium(III) oxide will form on surface of the steel)

Question 29

Name the 5 reactions taking place in blast furnace

Answer 29

1. Production of carbon monoxide: CO2 (g) + C (s) —> 2CO (g)
2. Production of carbon dioxide: C (s) + O2 (g) —> CO2 (g)
3. Reduction of haematite to iron: Fe2O3 (s) + 3CO (g) —> 2Fe (I) + 3CO2 (g)
4. Thermal decomposition of limestone: CaCO3 (s) —> CaO (s) + CO2 (g)
5. Removal of impurities: CaO (s) + SiO2 (s) —> CaSiO3 (I)

Question 30

What are the 3 starting ingredients you put at the top of a blast furnace?

Answer 30

Haematite, coke (carbon), limestone (calcium carbonate)