Substances From The Earth

Question 1

What is limestone primarily composed of?

Answer 1

Mainly from calcium carbonate (CaCO3) but in some instances dolomiteMgCO3 may be present

Question 2

What are the main uses of limestone?

Answer 2

• Making cement
• Road foundations and buildings
• Manufacturing quicklime (CaO) and slaked lime (Ca(OH)2)
• Construction (as an aggregate in concrete)

Question 3

What is the lime cycle?

Answer 3

Limestone is heated in a lime kiln at temperature above 840 degrees, it decomposes into calcium oxide and carbon dioxide.Thermal decomposition

Water is added to calcium oxide which makes calcium hydroxide ( slaked lime). Exothermic reaction

Calcium hydroxide and carbon dioxide are combined to produce calcium carbonate.

Question 4

What type of rock is limestone?

Answer 4

Limestone is a sedimentary rock made of shelled fragments,tiny fossils and other fossilized debris

Question 5

What is the typical coloration of limestone in Malta?

Answer 5

Limestone in Malta is yellowish

Question 6

How does limestone compare to marble and granite?
granite.

Answer 6

It is softer and less dense than both marble and

Question 7

limestone porous? What does this mean?

Answer 7

Yes, limestone is porous, meaning it allows liquids such as water to flow through it.

Question 8

How does limestone react to acidic water?

Answer 8

It deteriorates, this process happens naturally because rainwater is slightly acidic . However, acid rain speeds this process because it has a ph of less than 4.5

Question 9

Is limestone a good conductor of heat and electricity?

Answer 9

No, limestone is a poor conductor of both heat and electricity.

Question 10

How does limestone behave when exposed to fire?

Answer 10

It is fire-resistant but decomposes and loses its structural integrity at very high temperatures.

Question 11

What is concrete used for?

Answer 11

It is a major building material used in dams, buildings, and road construction.

Question 12

What are the main components of concrete?

Answer 12

• Aggregates (sand, gravel, crushed stone)
• Cement (binding material)
• Water

Question 13

How does concrete gain strength?

Answer 13

It gains strength over time as it dries and hardens.

Question 14

What is used to reinforce concrete for added strength?

Answer 14

Steel structures embedded within the concrete.

Question 15

What are the key properties of concrete?

Answer 15

• Durable and weather-resistant
• Fire-resistant
• Better insulator of heat compared to metals
• Non-conductor of electricity (if the steel reinforcement is not exposed)

Question 16

How does wood compare to limestone and concrete as a heat insulator?

Answer 16

Wood is a better heat insulator than both limestone and concrete.

Question 17

Is wood flammable?

Answer 17

Yes

Question 18

Is wood an electrical conductor or insulator?

Answer 18

Wood is an electrical insulator, but its conductivity increases as its moisture content rises.

Question 19

How is steel made?

Answer 19

By refining iron, removing impurities, and adding elements like manganese, chromium, nickel, tungsten, molybdenum, and vanadium.

Question 20

What is the melting point range of steel?

Answer 20

Between 1300°C and 1540°C.

Question 21

What are the main physical properties of steel?

Answer 21

• High strength
• Relatively low weight
• Durability
• Ductility
• Corrosion resistance

Question 22

What are the four major types of steel?

Answer 22

1. Carbon steel
2. Alloy steel
3. Stainless steel
4. Tool steel

Question 23

What I the primary ore of aluminum?

Answer 23

Bauxite

Question 24

How is aluminium extracted?

Answer 24

By electrolysis of alumina (Al2O3).

Question 25

What are the key properties of aluminium?

Answer 25

• Soft, durable, lightweight, ductile, and malleable • Good thermal and electrical conductor • Fairly corrosion-resistant due to an oxide layer • Recyclable • Low density

Question 26

What experiment can be used to investigate limestone's reaction with acids? 1. Add marble chips (CaCOs) to dilute hydrochloric acid (HCI). 2. Observe the reaction and test the gas with damp blue litmus paper. 3. Bubble the gas through lime water (Ca(OH) 2 solution).

Answer 26

1. Add marble chips (CaCOs) to dilute hydrochloric acid (HCI). 2. Observe the reaction and test the gas with damp blue litmus paper. 3. Bubble the gas through lime water (Ca(OH) 2 solution).

Question 27

What are the observations from the reaction of limestone with acid? .

Answer 27

• Effervescence (bubbling) occurs, indicating gas evolution. • Damp blue litmus paper turns red, showing the gas is acidic. • Lime water turns cloudy, confirming the presence of CO2.

Question 28

What is the chemical equation for the reaction between calcium carbonate and hydrochloric acid?

Answer 28

CaCO3 (s) + 2HCI (aq) → CaCl (aq) + CO2 (g) + H20 (1)

Question 29

How does acid rain affect limestone?

Answer 29

Acid rain (pH < 4.5) speeds up the weathering of limestone by reacting with it.

Question 30

What is concrete made of?

Answer 30

A composite material consisting of a filler (aggregate) and a binder (cement).

Question 31

How is cement made?

Answer 31

By burning limestone and clay together at 1400-1600°C.

Question 32

Is concrete impermeable to water?

Answer 32

Yes, it is impermeable to pure water but reacts with acidic water, leading to deterioration.

Question 33

How does acid rain affect limestone?

Answer 33

Acid rain (pH < 4.5) speeds up the weathering of limestone by reacting with it.

Question 34

How does acidic water affect concrete?

Answer 34

The alkaline components in cement react with acid, causing concrete deterioration. The lower the pH, the faster the deterioration.

Question 35

What happens when aluminium reacts with air?

Answer 35

It forms a protective layer of aluminium oxide (Al

Question 36

What is the chemical equation for aluminium reacting with oxygen?

Answer 36

4AI (s) +302(9) → 2A1203 (s)

Question 37

Under what conditions does aluminium react with acids without removing the oxide layer?

Answer 37

When the acid is moderately concentrated and the reaction mixture is heated to several hundred degrees Celsius.

Question 38

What is the reaction of aluminium with hydrochloric acid?

Answer 38

2AI (s) + 6HCI (g) → 2AICls (s) + 3H2 (g)

Question 39

Does aluminium react with water at room temperature?

Answer 39

No,but it reacts with steam 2AI (s) + 3H20 (g) → Al2O3 (s) + 3H2 (g)

Question 40

What is steel mostly made of?

Answer 40

An alloy of iron and carbon.

Question 41

Why are alloys used?

Answer 41

To enhance metal properties such as strength and corrosion resistance.

Question 42

What causes steel to rust?

Answer 42

Reaction with oxygen and water vapour in the air, forming hydrated iron (Ill) oxide.

Question 43

How can steel be protected from corrosion?

Answer 43

Using stainless steel, which contains elements that increase resistance to corrosion.

Question 44

How can steel be protected from corrosion?

Answer 44

Using stainless steel, which contains elements that increase resistance to corrosion.

Question 45

Why does wood shrink and crack in dry seasons?

Answer 45

Due to loss of moisture.

Question 46

What happens to wood in hot and humid conditions?

Answer 46

It expands. Denser wood expands and contracts less.

Question 47

How does acid deposition (e.g., acid rain) affect unpainted wood?

Answer 47

It accelerates deterioration by reacting with cellulose, which provides structural integrity.

Question 48

How can wood be protected from acid rain?

Answer 48

By painting it before exposure. Painted wood is not affected by acid deposition.

Question 49

What is an advantage of limestone quarrying in terms of resource availability?

Answer 49

Limestone is a readily available and cheap resource.

Question 50

How does limestone quarrying contribute to saving trees?

Answer 50

It decreases the use of wood, which helps save trees from being cut down.

Question 51

What is a major environmental disadvantage of limestone quarrying?

Answer 51

It destroys agricultural land and wildlife habitats.

Question 52

What types of pollution are created by limestone quarrying?

Answer 52

• Noise pollution • Dust pollution • Air pollution from heavy trucks

Question 53

Why is limestone quarrying considered unsustainable?

Answer 53

Limestone is a non-renewable resource, so quarrying it can deplete the resource.

Question 54

What are ores?

Answer 54

Ores are rocks found in the Earth's crust that contain free metals and/or metal compounds.

Question 55

Where are metals that are chemically unreactive found?

Answer 55

These metals are found in their free (native) state in the Earth's crust. Examples include gold and platinum.

Question 57

How are more reactive metals found in nature?

Answer 57

More reactive metals are found combined with other elements and must be chemically extracted from ores. Examples include iron from haematite and aluminium from bauxite.

Question 58

What does the method of extraction of metals depend on?

Answer 58

It depends on the reactivity of the metal.

Question 59

What determines the order of reactivity of metals?

Answer 59

The order of reactivity can be determined by reacting metals with substances such as oxygen, water/steam, hydrochloric acid, and by means of displacement reactions.

Question 60

What happens in a displacement reaction?

Answer 60

A more reactive metal displaces a less reactive metal from its compound, leaving the less reactive metal uncombined.

Question 61

How can magnesium and copper sulfate demonstrate a displacement reaction?

Answer 61

Magnesium is more reactive than copper. When magnesium is dipped into copper (Il) sulfate solution, magnesium displaces copper, producing magnesium sulfate and copper metal. Equation: Mg(s) + CUSO(aq) → Cu(s) + MgSO (aq)