Using resources

A factory uses crude oil to make polymer fibres and timber from a replanted forest to make boards. Classify each raw material as finite or renewable.

A mineral reserve contains $4.8\times10^8$ kg of usable ore. It is extracted at $6.0\times10^7$ kg per year. Calculate how many years the reserve would last if the rate stayed constant, and explain why the ore is finite.

A building company compares insulation for a $40$-year project. Straw panels use a renewable crop, last $20$ years, require $12$ tonnes per installation and use $1.1$ GJ of processing energy per tonne. Polymer panels use a finite raw material, last $40$ years, require $8$ tonnes and use $4.6$ GJ per tonne. Evaluate which choice is more sustainable. Use calculations.

Explain why potable water can be safe to drink without being pure water in the chemical sense.

Describe how fresh water containing mud particles and harmful bacteria is treated to make potable water. Give the purpose of each treatment step.

An island must desalinate $1.5\times10^6$ litres of sea water each day. Distillation would use $2.8$ MJ per litre and reverse osmosis would use $0.018$ MJ per litre. Calculate the daily energy saved by reverse osmosis and evaluate its use if membranes need regular replacement.

State the two treatment stages used before sewage is allowed to settle and name the two products of sedimentation.

Explain how the sludge and effluent from a sedimentation tank are treated biologically.

A treatment works processes $9.5\times10^3$ m³ of sewage in one day. Sedimentation separates $7.0\%$ of this volume as sludge. Calculate the sludge volume and explain why making potable water from treated waste water is generally harder than making it from fresh ground water.

Describe how phytomining produces material containing copper compounds.

Bioleaching produces a solution containing copper compounds. Explain how scrap iron can be used to obtain copper from this solution.

A conventional process yields $760$ kg of copper using $5.4$ GJ and moves $320$ tonnes of rock in $2$ days. A bioleaching process yields $690$ kg using $1.7$ GJ, moves $38$ tonnes of residue and takes $60$ days. Calculate the energy used per kilogram of copper for each process and evaluate bioleaching.

State the four main stages considered in a life cycle assessment.

A reusable food container takes $14$ MJ to manufacture, is used $100$ times and takes $0.030$ MJ to wash after each use. A disposable container takes $0.24$ MJ to manufacture and is used once. Calculate the lifetime energy per use for each container.

Two protective packages perform the same job. Package A uses $1.8$ MJ in manufacture, $0.40$ MJ in transport and produces $60$ g of end-of-life waste; its pollutant-effect score is $2$. Package B uses $0.90$ MJ in manufacture, $1.1$ MJ in transport and produces $25$ g of waste; its pollutant-effect score is $7$. Evaluate the packages and explain one limitation of the comparison.

Give one example each of reducing, reusing and recycling a material resource.

Producing a metal from ore uses $15.2$ MJ kg^-1, while producing it from sorted scrap uses $1.8$ MJ kg^-1. Calculate the energy saved when $840$ kg is produced from scrap.

For $6000$ deliveries, a company can use $0.12$ kg single-use trays or reusable crates. Each $9.0$ kg crate lasts $120$ deliveries. Single-use trays require $3.0$ MJ kg^-1 to make. Crates require $5.5$ MJ kg^-1 to make and $0.10$ MJ of washing energy per delivery. Evaluate the switch to crates using raw-material mass and energy.

State the two substances that must both be present for iron to rust.

Plan an experiment using three identical iron nails to show that both air and water are needed for rusting.

Iron harbour bolts can be coated with metal X or copper. The reactivity order is magnesium, X, iron, copper. Evaluate the protection given by each coating if it is scratched through to the iron.

Name the two metals in bronze and the two metals in brass.

Identify the most suitable steel — high-carbon, low-carbon or stainless — for each use: a cutting blade, a pressed car-body panel and a kitchen sink. Justify each choice.

A $2.40$ kg brass fitting contains $68.0\%$ copper by mass and the rest is zinc. Calculate the mass of zinc. Explain why a manufacturer might use this brass rather than pure copper when data show brass is harder but slightly less electrically conductive.

Glass fibres are surrounded and held together by a polymer resin in a composite. Identify the reinforcement and the matrix.

Explain, in terms of structure, why a thermosoftening polymer melts when heated but a thermosetting polymer does not.

A transparent oven window must work at $720$ °C. Soda-lime glass softens at $650$ °C. Borosilicate glass softens at $900$ °C, is transparent and has density $2.25$ g cm^-3. An opaque clay ceramic works to $1100$ °C. Identify the most suitable material and calculate the mass of an $80$ cm³ window.

State the source of nitrogen, the usual source of hydrogen and the catalyst used in the Haber process.

Explain how ammonia is separated from the gases leaving a Haber reactor and why the remaining gases are returned to the reactor.

A plant sends $800$ kg of a nitrogen-hydrogen mixture through a Haber reactor. After one pass, $184$ kg of ammonia is separated. Calculate the percentage of the feed converted to ammonia in this pass and explain what happens to the remaining gases.

State what the letters N, P and K represent on an NPK fertiliser label and explain why phosphate rock is not used directly as a fertiliser.

Name one useful salt formed when phosphate rock is treated with each acid: nitric acid, sulfuric acid and phosphoric acid.

A laboratory batch makes $35$ g of ammonium salt every $45$ minutes. An integrated industrial process operates continuously at $2.4$ kg per minute. Calculate the mass each route makes in $3.0$ hours and compare the routes for large-scale fertiliser production.