Topic 10 Flashcards

Finite & Renewable Resources

Finite & Renewable Resources: read all 5 questions and answers

1. What is a finite resource?
   A NON-RENEWABLE resource that cannot be replaced over a human timescale once used. Examples: fossil fuels (coal, oil, gas), metal ores.
2. What is a renewable resource?
   A resource that can be REPLENISHED naturally at a rate fast enough for human use. Examples: timber, crops, fresh water (via the water cycle).
3. Define sustainable development.
   Meeting the needs of the CURRENT generation without compromising the ability of FUTURE generations to meet their own needs.
4. Give three examples of how chemistry contributes to sustainable development.
   1. Developing ALTERNATIVE FUELS (hydrogen, biofuels). 2. Creating biodegradable polymers. 3. Improving recycling processes for metals and plastics.
5. Why is copper an important finite resource?
   Copper is essential for electrical wiring and plumbing. Traditional mining of high-grade ores is becoming less viable, so phytomining and bioleaching are used for low-grade ores.

Potable Water & Desalination

Potable Water & Desalination: read all 6 questions and answers

1. What is potable water?
   Water that is SAFE TO DRINK. It is NOT pure in the chemistry sense - it contains dissolved substances, but at levels low enough to be safe.
2. What are the 3 steps to produce potable water in the UK?
   1. Choose a freshwater SOURCE (rivers, reservoirs, aquifers). 2. FILTRATION through filter beds (removes debris and some microbes). 3. STERILISATION with chlorine, ozone, or UV light (kills bacteria/pathogens).
3. Why is potable water NOT the same as pure water?
   Potable water contains dissolved minerals at SAFE concentrations. Pure water (in chemistry) contains ONLY water molecules (H₂O) and nothing else.
4. What is desalination?
   The process of removing dissolved SALTS from sea water to produce potable water. Used in arid regions with limited fresh water.
5. Name 2 methods of desalination and their drawbacks.
   1. DISTILLATION - boiling sea water and condensing steam. Very ENERGY-INTENSIVE. 2. REVERSE OSMOSIS - forcing water through a membrane at high pressure, which traps salt ions. More efficient but membranes are expensive.
6. What happens in the Required Practical for water purification?
   1. Test pH of water samples. 2. Measure dissolved solids by evaporation. 3. DISTIL the water - boil, condense, collect. 4. Compare distillate with original - should be neutral pH with fewer dissolved solids.

Waste Water Treatment & Extraction

Waste Water Treatment & Extraction: read all 6 questions and answers

1. What are the 4 stages of waste water treatment?
   1. SCREENING - remove large objects. 2. SEDIMENTATION - solids settle as sludge; liquid is effluent. 3. AEROBIC biological treatment - bacteria break down organic matter. 4. SLUDGE treatment - anaerobic bacteria digest sludge, producing BIOGAS (methane).
2. What is the difference between sludge and effluent?
   SLUDGE = the solid material that settles out during sedimentation. EFFLUENT = the liquid part that floats above the sludge.
3. What useful by-product comes from sludge digestion?
   BIOGAS (mainly methane, CH₄). It is produced by ANAEROBIC bacteria and can be used as a fuel. The remaining dried sludge can be used as fertiliser.
4. What is phytomining?
   Growing plants on LOW-GRADE ore. Plants absorb metal compounds through roots. Plants are harvested, BURNED, and the metal-rich ash is processed to extract the metal.
5. What is bioleaching?
   Using BACTERIA to produce a leachate solution containing dissolved metal compounds from low-grade ores. The metal is then extracted by DISPLACEMENT (with scrap iron) or ELECTROLYSIS.
6. Why are phytomining and bioleaching useful?
   They extract metals from LOW-GRADE ORES that would be uneconomical to mine traditionally. They use LESS ENERGY and cause LESS environmental damage, though they are SLOWER.

Life Cycle Assessments & Recycling

Life Cycle Assessments & Recycling: read all 6 questions and answers

1. What is a Life Cycle Assessment (LCA)?
   An assessment of the ENVIRONMENTAL IMPACT of a product at EVERY STAGE of its life - from "cradle to grave": raw materials → manufacturing → use → disposal.
2. Name the 4 stages of a Life Cycle Assessment.
   1. RAW MATERIALS - extracting and processing. 2. MANUFACTURING - energy and pollution. 3. USE - energy, emissions, maintenance. 4. DISPOSAL - landfill, incineration, or recycling.
3. What is a major limitation of LCAs?
   Some impacts are hard to QUANTIFY OBJECTIVELY. LCAs involve SUBJECTIVE VALUE JUDGEMENTS about the relative importance of different environmental impacts, making them potentially biased or misleading.
4. What is the waste hierarchy?
   1. REDUCE (best) - use fewer resources. 2. REUSE - use products again. 3. RECYCLE - process used materials into new products. Reducing is always the best option.
5. Give 4 benefits of recycling metals.
   1. Reduces waste sent to LANDFILL. 2. CONSERVES finite resources. 3. Reduces ENERGY consumption (e.g. Recycling aluminium uses 95% LESS energy than extraction). 4. Reduces GREENHOUSE GAS emissions.
6. Compare paper bags vs plastic bags using LCA thinking.
   Paper: renewable raw material, biodegradable, but more energy and water to manufacture. Plastic: fossil fuel raw material, non-biodegradable, but lighter (lower transport emissions) and cheaper to make. Neither is clearly "better" - LCA depends on what impacts you prioritise.

Corrosion & Prevention Chemistry Only

Corrosion & Prevention: read all 6 questions and answers

1. What is corrosion?
   The DESTRUCTION of materials by chemical reactions with substances in the environment. The most common example is the RUSTING of iron.
2. What two conditions are needed for iron to rust?
   Both WATER and OXYGEN must be present. Iron + water + oxygen → hydrated iron(III) oxide (rust).
3. Name 4 ways to prevent corrosion.
   1. PAINTING / oiling / greasing (barrier). 2. GALVANISING (zinc coating - barrier + sacrificial). 3. SACRIFICIAL PROTECTION (blocks of zinc/magnesium). 4. ELECTROPLATING (thin metal layer via electrolysis).
4. What is sacrificial protection?
   Attaching blocks of a MORE REACTIVE metal (e.g. Zinc or magnesium) to iron. The more reactive metal OXIDISES PREFERENTIALLY, protecting the iron. Used on ship hulls and pipelines.
5. Why does galvanising protect iron even when scratched?
   Zinc is MORE REACTIVE than iron, so even if the zinc coating is scratched and iron is exposed, the zinc corrodes PREFERENTIALLY (sacrificial protection). It's both a barrier AND sacrificial method.
6. Why does aluminium not corrode visibly?
   Aluminium reacts with oxygen to form a TOUGH, PROTECTIVE layer of aluminium oxide (Al₂O₃) on its surface. This prevents further corrosion (unlike iron oxide / rust, which is flaky and allows more reaction).

Materials & The Haber Process Chemistry Only

Materials & The Haber Process: read all 8 questions and answers

1. Why are alloys harder than pure metals?
   Different-sized atoms DISRUPT the regular layers of metal atoms, preventing them from SLIDING over each other. This makes alloys harder and stronger.
2. Give 3 examples of alloys.
   1. STEEL - iron + carbon. 2. BRASS - copper + zinc. 3. BRONZE - copper + tin.
3. What are the key properties of ceramics?
   Hard, strong, heat-resistant, very HIGH MELTING POINTS, but BRITTLE (break rather than bend). Examples: glass, clay pottery, cement, bricks.
4. What is a composite? Give 3 examples.
   A material made from TWO OR MORE different materials bonded together, combining properties of each. Examples: CONCRETE (aggregate + cement), FIBREGLASS (glass fibres + resin), CARBON FIBRE (carbon fibres + polymer).
5. What does the Haber process produce and what equation?
   AMMONIA (NH₃). Equation: N₂(g) + 3H₂(g) ⇌ 2NH₃(g). The reaction is REVERSIBLE and EXOTHERMIC (ΔH = −92 kJ/mol).
6. What conditions are used in the Haber process?
   Temperature: ~450°C (COMPROMISE). Pressure: ~200 atm (high pressure favours forward). Catalyst: IRON (speeds up rate, doesn't change yield). Unreacted gases are RECYCLED.
7. Why is 450°C a compromise for the Haber process?
   Forward reaction is EXOTHERMIC, so LOWER temperature = higher yield (Le Chatelier's). BUT lower temperature = slower rate. 450°C gives a reasonable yield at an acceptable rate.
8. What are NPK fertilisers?
   Fertilisers providing three essential elements: Nitrogen (N), Phosphorus (P), and Potassium (K). Ammonia from the Haber process is reacted with acids to make ammonium salts for fertiliser (e.g. NH₄NO₃).