Using resources

• Resources are used, reused and recycled; potable water 饮用水 — filtered and sterilised fresh water, or desalinated sea water — is the first essential.
• Life cycle assessment 生命周期评估s weigh a product's environmental cost stage by stage; reduce–reuse–recycle cuts every stage.
• (Chem) corrosion 腐蚀 prevention, alloys, ceramics/polymers/composite 复合材料s, and the Haber process 哈伯法's compromise chemistry.

Humans use the Earth's resources for warmth, shelter, food and transport; finite resources (ores, fossil fuels) are processed for energy and materials; renewable ones replenish. Sustainable development 可持续发展 meets present needs without compromising future generations.

Potable water — safe to drink: low dissolved salts and microbes — but not pure water (it contains dissolved substances).

In the UK, fresh rainwater is made potable by: choosing a source → filter beds → sterilising (with chlorine, ozone or UV light). Where fresh water is scarce, desalination — distillation or reverse osmosis — needs large amounts of energy.

Waste water (sewage) treatment: screening and grit removal → sedimentation (sewage sludge + effluent) → anaerobic digestion of the sludge → aerobic biological treatment of the effluent. Potable water is easiest from ground water, harder from waste, hardest (energy-wise) from salt water.

(HT) Alternative metal extraction — copper ores are scarce: phytomining (plants absorb metal compounds; harvest, burn to ash, extract) and bioleaching (bacteria produce leachate solutions of the metal compounds) avoid moving huge amounts of rock.

LCA stages: extracting and processing raw materials; manufacturing and packaging; use and operation; disposal — including transport at each stage. Energy, water, resource use and waste are quantifiable; pollutant effects need value judgements — so LCAs are not purely objective, and selective LCAs can be misused (advertising). Compare plastic vs paper shopping bags.

Reduce, reuse, recycle: metals, glass, building materials, clay ceramics and most plastics come from limited raw materials; recycling cuts mining/quarrying impact and energy — e.g. glass crushed and remelted; scrap steel added to the blast furnace reduces iron-ore extraction. Some products (glass bottles) are reused; others recycled into different products; separation effort depends on the final product's requirements.

Corrosion — destruction of materials by chemical reaction with the environment (e.g. iron + oxygen + water → rust). Prevention: greasing, painting, coating (galvanising with zinc, which gives sacrificial protection 牺牲保护 — it corrodes in place of the iron even when scratched) and alloying (stainless steel). Aluminium resists corrosion by its own protective oxide layer.

Alloys: bronze (copper + tin), brass (copper + zinc); gold jewellery alloyed with silver/copper/zinc — purity in carats (24 = 100 %; 18 = 75 %). Steels — iron + carbon (+ metals): high-carbon steel strong but brittle; low-carbon steel softer, shaped easily; stainless steel (Cr, Ni) hard and corrosion-resistant; aluminium alloys low density (aircraft).

Ceramics, polymers, composites: soda-lime glass (sand + sodium carbonate + limestone), borosilicate glass (sand + boron trioxide — higher melting point); clay ceramics (pottery, bricks — shaped wet clay, then fired). Polymers depend on monomers and conditions — LD and HD poly(ethene) both from ethene. Thermosoftening polymers melt on heating (recyclable chains); thermosetting polymer 热固性聚合物 does not (cross-links). Composites — a matrix/binder surrounding a reinforcement (fibres/fragments); know examples (fibreglass, concrete, carbon-fibre).

Haber process: N₂ + 3 H₂ ⇌ 2 NH₃ — nitrogen from air, hydrogen from natural gas (methane + steam) [or electrolysis of water]. Conditions: iron catalyst, ~450 °C, ~200 atmospheres; the reaction is reversible — cool the mixture, the ammonia liquefies and is removed; unreacted N₂/H₂ are recycled.

(HT) Higher pressure favours ammonia (fewer gas molecules) but is expensive and unsafe; lower temperature favours the exothermic forward reaction but is slow — so the chosen conditions are a compromise between rate, yield and cost. Apply Le Chatelier to each condition change.

NPK fertilisers — formulations of nitrogen, phosphorus and potassium compounds for plant growth: ammonia → nitric acid (Ostwald); ammonia + nitric acid → ammonium nitrate; potassium chloride/potassium sulfate mined; phosphate rock treated with acid to make superphosphate. Evaluate the industrial production of fertilisers given data (raw materials, energy costs, % yield — e.g. the lab vs industrial ammonium sulfate routes).

• Potable vs pure; the UK treatment sequence; desalination and its cost; sewage-treatment steps in order.
• (HT) phytomining and bioleaching described end to end.
• LCA four stages with the objectivity caveat; reduce-reuse-recycle examples with reasons.
• (Chem) corrosion prevention incl. sacrificial zinc; named alloys with compositions; thermosoftening vs thermosetting; matrix + reinforcement.
• (Chem/HT) Haber conditions with the compromise explained by equilibrium; the NPK compounds and their origins.