USING RESOURCES

Question 1

Define corrosion

Answer 1

Corrosion is the destruction of a metal by chemical reactions with substances in the environment, often involving oxidation by oxygen and water.

Question 2

Describe ways to prevent corrosion

Answer 2

• Applying barrier coatings such as paint, oil/grease, or plastic to prevent oxygen and water reaching the metal.
• Electroplating the metal with a less reactive metal to form a protective surface.
• Galvanising (coating iron/steel with zinc), which acts as both a barrier and provides sacrificial protection because zinc is more reactive and corrodes instead of the iron.
• Using sacrificial protection directly by attaching blocks of a more reactive metal (e.g. magnesium or zinc) so that this metal oxidises in place of the protected metal.

Question 3

Explain how sacrificial methods work to prevent corrosion

Answer 3

Sacrificial protection works by attaching a more reactive metal (such as magnesium or zinc) to the metal being protected. The more reactive metal oxidises more easily, so it corrodes instead of the iron or steel. This prevents the protected metal from losing electrons and stops it from corroding.

Question 4

Explain how the properties of materials are related to their uses

Answer 4

• Metals are strong and malleable → used for construction, car bodies, and machinery.
• Aluminium is low density and resistant to corrosion → used for aircraft and drink cans.
• Copper conducts electricity → used for wiring and electrical circuits.
• Polymers can be flexible, waterproof, or insulating → used for plastic pipes, clothing, and electrical insulation.
• Ceramics are hard and heat-resistant → used for tiles, pottery, and ovenware.

Question 5

Discuss the different types of polymers

Answer 5

1. Thermosoftening polymers (thermoplastics)
   • Made of long, unbranched chains held together by weak intermolecular forces.
   • Soften when heated and can be remoulded multiple times.
   • Examples: poly(ethene), poly(propene) and used in plastic bottles, pipes.
   
   2. Thermosetting polymers (thermosets)
      • Made of chains linked by strong covalent cross-links.
      • Do not soften when heated; they retain their shape and are hard and rigid.
      • Examples: epoxy resins and used for electrical insulation, adhesives, kitchenware.

Question 6

Explain what composites are with examples and benefits

Answer 6

Composites are materials made from two or more different materials with different properties that, when combined, produce a material with improved overall properties.

Examples:
• Fibreglass: glass fibres in a polymer matrix → strong, lightweight → used in boats and car bodies.
• Concrete: cement mixed with sand and aggregate → strong in compression → used in buildings.
• Carbon-fibre-reinforced polymer (CFRP): carbon fibres in polymer → very strong, very light → used in aircraft and sports cars.

Benefits of composites:
• Improved strength and stiffness compared to individual components.
• Lightweight (especially fibreglass and carbon fibre).
• Durability and resistance to corrosion (fibreglass does not rust).
• Can be tailored for specific properties depending on the materials used.

Question 7

Describe the haber process

Answer 7

The Haber process is used to synthesise ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂) gases.

Question 8

Compare industrial production of fertilisers with the laboratory preparations

Question 9

Describe NPK fertilisers and the compounds they are composed of

Answer 9

NPK fertilisers are fertilisers that provide three essential nutrients for plant growth:
1. Nitrogen (N) – promotes leaf and stem growth.
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2. Phosphorus (P) – promotes root growth and flowering.
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3. Potassium (K) – promotes flowering, fruiting, and disease resistance.

Question 10

Advantages and disadvantages of LCA’s

Answer 10

Advantages:
• Identifies stages with the largest environmental impact, helping to reduce pollution and energy use.
• Encourages more sustainable design and materials choice.
• Can inform consumers and manufacturers about environmental effects.

Disadvantages:
• Can be biased, depending on which impacts are considered and how data is collected.
• Time-consuming and expensive to carry out.
• Does not always give clear answers, as some impacts (e.g., visual pollution, biodiversity) are hard to quantify.

Question 11

Evaluate reduction with carbon to extract metals

Answer 11

1. Reduction with carbon
   • Suitable for less reactive metals (e.g., iron, zinc).
   • Metal oxides are reduced by carbon in a blast furnace.
   • Advantages: cheap, simple, widely used.
   • Disadvantages: produces CO₂ → contributes to global warming.

Question 12

Difference between finite and renewable

Answer 12

• Finite resources are resources that exist in limited amounts and cannot be replaced on a human timescale once used, e.g., coal, oil, natural gas, metals.
• Renewable resources are resources that can be replaced naturally at a similar rate to their use, e.g., solar energy, wind energy, timber, crops.

Question 13

What is sustainable development?

Answer 13

Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

Question 14

What is potable water

Answer 14

Potable water is water that is safe to drink because it has been treated to remove harmful chemicals and microbes, but it may still contain dissolved minerals.

Question 15

Required practical for purification of water samples

Question 16

Describe the process of sewage treatment

Answer 16

1. Screening – Large objects such as plastic and grit are removed using screens and grit traps.
   
   2. Sedimentation / Primary treatment – Sewage is allowed to settle in a tank, so solids (sludge) sink and fats or lighter materials float and are removed.
   3. Biological treatment / Secondary treatment – Aerobic bacteria break down the remaining organic matter, reducing the biochemical oxygen demand (BOD).
   4. Disinfection / Tertiary treatment (optional) – Chemicals or UV light are used to kill any remaining microbes.
   5. Sludge treatment – The collected sludge undergoes anaerobic digestion to produce biogas, and the remaining solids can be used as fertiliser.

Question 17

Conditions for the haber process

Answer 17

• Temperature: ~450 °C → compromise between a reasonable rate and good yield.
• Pressure: 200 atm → high pressure favours the forward reaction (fewer gas molecules).
• Catalyst: iron with potassium hydroxide promoter → speeds up the reaction without affecting yield.

Question 18

Catalyst used in haber process

Answer 18

Iron

Question 19

Evaluate electrolysis to extract metals

Answer 19

2. Electrolysis
   • Used for more reactive metals (e.g., aluminium, sodium).
   • Metal is extracted by passing electric current through molten or aqueous compounds.
   • Advantages: can extract highly reactive metals.
   • Disadvantages: very expensive, high energy consumption, costly.

Question 20

What are LCAs?

Answer 20

Life Cycle Assessment (LCA) evaluates the environmental impact of a product over its entire life, from raw material extraction to disposal.