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neurologyYou need to know

• Finite resources, such as metal ores, are used faster than they are replaced, whereas renewable resources can be replenished naturally at a rate comparable to their use.
• Reusing products avoids making replacements, while recycling processes waste materials into new products and can reduce raw material extraction, energy use and landfill waste.
• Limited supplies of metal ores can be conserved by reducing metal use, repairing and reusing products, recycling metals and substituting suitable alternative materials.
• A life cycle assessment (LCA) assesses the environmental impacts of a product throughout its life so that products, materials or manufacturing methods can be compared.
• The main stages of an LCA are extracting and processing raw materials, manufacturing and packaging, transport and distribution, use, and end-of-life reuse, recycling or disposal.
• LCAs consider resource consumption, energy use, emissions and waste, but conclusions depend on the available data, the stages included and how different impacts are weighted.
• Pure water contains only water molecules, whereas potable water is safe to drink but may contain dissolved salts and other substances at safe concentrations.
• Groundwater treatment depends on its quality and can include filtration to remove suspended particles and sterilisation using chlorine, ozone or ultraviolet light to kill microorganisms.
• Desalination removes dissolved salts from seawater by distillation or reverse osmosis, but both methods require substantial energy for heating or generating high pressure.
• Simple distillation separates water from dissolved salts by evaporation followed by condensation, while reverse osmosis forces water through a membrane that allows water molecules through but rejects most dissolved salts.
• Pure water has a boiling point of approximately 100°C at standard atmospheric pressure and leaves no dissolved-solid residue when evaporated, although these tests alone cannot establish that water is safe to drink.
• Initial wastewater treatment uses screening and grit removal to remove large objects and grit, followed by sedimentation to separate settled sewage sludge from liquid effluent.
• Liquid effluent undergoes aerobic biological treatment, in which microorganisms use oxygen to break down organic matter, before further settling and any additional treatment needed for safe discharge.
• Sewage sludge undergoes anaerobic digestion, in which microorganisms break down organic matter without oxygen and produce methane-containing biogas that can be burned as a fuel.
• High-grade copper ores contain a higher proportion of copper than low-grade ores, so less rock generally needs to be processed to obtain the same mass of copper.
• Copper can be extracted from copper oxide by reduction with carbon, while copper sulfide ores are commonly concentrated and smelted, potentially releasing sulfur dioxide.
• Dilute sulfuric acid reacts with copper oxide in an ore to produce copper sulfate solution and water, leaving insoluble impurities that can be removed by filtration.
• During electrolysis of copper sulfate solution using inert electrodes, copper ions gain electrons and form copper metal at the negative electrode, while oxygen forms at the positive electrode.
• Phytomining uses plants to absorb copper compounds from soil, after which the plants are harvested and burned and the ash is processed to obtain a solution containing copper ions.
• Bioleaching uses bacteria to help produce a leachate containing copper ions from low-grade ores, and copper can be recovered from this solution by displacement with iron or by electrolysis.

• Extract and interpret resource, water-treatment or LCA data from graphs, charts and tables, using headings, scales and units correctly and calculating relevant differences or percentages.
• Evaluate ways to conserve metal ores by comparing reduction, repair, reuse, recycling and substitution in terms of resource savings, energy demand, cost and practical limitations.
• Evaluate a material or product using LCA evidence across all key stages, comparing products that perform the same function and identifying missing data or subjective judgements.
• Compare filtration, sterilisation, distillation and reverse osmosis by identifying which contaminants each removes or destroys and evaluating their suitability, energy demand and cost.
• Carry out simple distillation using an unsealed apparatus, gently heating the water sample and passing its vapour through a condenser with cooling water entering at the bottom to collect distillate separately.
• Assess a water sample and its distillate by measuring boiling temperature and evaporating small samples to check for dissolved-solid residue, recognising the limitations of these purity tests.
• Extract copper compounds from a copper oxide-rich ore by adding dilute sulfuric acid, stirring and gently warming if necessary, then filtering to obtain copper sulfate solution while wearing eye protection.
• Recover copper from copper sulfate solution by electrolysis using inert electrodes and a low-voltage direct-current supply, identifying the copper deposit at the negative electrode and handling copper-containing waste safely.
• Evaluate conventional copper extraction, phytomining and bioleaching using evidence about ore grade, extraction rate, energy use, cost, land disturbance and pollution.