Using resources — AQA GCSE Chemistry

The 'Using resources' topic in AQA GCSE Chemistry explores how humans use Earth's natural resources sustainably. It covers the difference between finite and renewable resources, the importance of recycling, and methods to reduce waste. Students learn about life cycle assessments (LCAs) to evaluate the environmental impact of products from extraction to disposal. This topic is crucial for understanding modern challenges like climate change and resource depletion, linking chemistry to real-world issues in industry and sustainability.

Key areas include the extraction and processing of metal ores, the use of crude oil for fuels and plastics, and the production of potable water. The topic also introduces alternative resources such as bioplastics and composite materials. By studying this, students appreciate how chemical processes can be optimized to minimize environmental harm, aligning with the broader goal of sustainable development. This knowledge is essential for informed citizenship and future careers in environmental science, engineering, or policy.

Within the wider subject, 'Using resources' connects to topics like the Earth's atmosphere, chemical reactions, and energy changes. It builds on earlier work about the reactivity series and organic chemistry, applying these concepts to resource management. Mastery of this topic enables students to critically evaluate claims about 'green' products and understand the trade-offs in material choices, preparing them for both exams and real-life decision-making.

• →Finite vs renewable resources: Finite resources (e.g., fossil fuels, metal ores) are limited and will run out; renewable resources (e.g., timber, fresh water) can be replenished at a similar rate to their use.
• →Life cycle assessment (LCA): A systematic analysis of the environmental impact of a product across its entire life—from raw material extraction, manufacturing, use, to disposal. LCAs consider energy use, resource depletion, pollution, and waste.
• →Recycling and reuse: Recycling saves energy and resources compared to extracting and processing raw materials. For example, recycling aluminium uses only 5% of the energy needed to produce it from bauxite ore.
• →Potable water: Water that is safe to drink. Methods to produce potable water include sedimentation, filtration, and chlorination (or other disinfection). In the UK, most potable water comes from freshwater sources; in arid regions, desalination of seawater is used but is energy-intensive.
• →Alternative resources: Bioplastics (made from plant materials like corn starch) are biodegradable but may require specific conditions to break down. Composite materials (e.g., fibreglass) combine two or more materials to improve properties like strength or weight.

• Distinguish between finite and renewable resources
• Explain the stages of producing potable water (filtration, sedimentation, sterilization)
• Describe the processes of phytomining and bioleaching for metal extraction
• Identify the four stages of a Life Cycle Assessment (LCA)
• Explain the necessity of both air and water for iron to rust
• Describe sacrificial protection and the use of coatings to prevent corrosion
• Explain the differences between thermosoftening and thermosetting polymers
• Recall the raw materials and conditions for the Haber process
• Explain the trade-off between rate and yield in the Haber process
• Describe the production of NPK fertilizers from phosphate rock

• 💡When evaluating metal extraction methods, always refer to the specific advantages (e.g., low-grade ores) and disadvantages (e.g., slow rate)
• 💡Use the term 'potable' correctly; it does not mean 'pure'
• 💡For the Haber process, ensure you can explain why 450°C is a compromise temperature (rate vs yield)
• 💡When discussing LCAs, emphasize that assigning numerical values to environmental impacts is subjective
• 💡When answering questions on LCAs, always mention specific stages (e.g., extraction, manufacturing, transport, use, disposal) and give examples of impacts (e.g., CO2 emissions, habitat destruction). Avoid vague statements like 'it's bad for the environment'—be precise.
• 💡For potable water questions, remember the difference between pure water (H2O only) and potable water (contains dissolved salts, safe to drink). Know the steps: sedimentation (settling of solids), filtration (removing fine particles), and chlorination (killing microbes). In the UK, we don't need to desalinate because we have ample freshwater.
• 💡When comparing materials (e.g., plastic vs paper bags), use an LCA approach. Consider factors like raw material source, energy in production, transport weight, reusability, and disposal method. A paper bag may be biodegradable but requires more energy to produce and is heavier to transport.

• Confusing potable water with pure water
• Failing to mention that both air and water are required for iron to rust
• Misinterpreting the LCA process as purely objective rather than involving value judgments
• Assuming phosphate rock can be used directly as a fertilizer without treatment
• Confusing the properties of thermosoftening and thermosetting polymers
• Misconception: 'Renewable resources can never run out.' Correction: Renewable resources can be depleted if used faster than they are replenished (e.g., overfishing, deforestation). Sustainable use means using them at a rate that allows natural regeneration.
• Misconception: 'Recycling always saves energy.' Correction: While recycling often saves energy, it still requires energy for collection, sorting, and reprocessing. For some materials (e.g., certain plastics), the energy saved may be minimal, and the process may produce pollution. LCAs help compare overall impacts.
• Misconception: 'Biodegradable plastics are always better for the environment.' Correction: Biodegradable plastics may not degrade in landfill conditions (which lack oxygen and light). They can also contaminate recycling streams. Their production may use land and water resources, so the full LCA must be considered.