Year 8 answers
Classifying resources
- (a) Renewable, (b) non-renewable, (c) non-renewable, (d) renewable, (e) renewable (managed), (f) non-renewable.
- Any two of: coal, oil, natural gas.
- Coal: Latrobe Valley (VIC) or Hunter Valley (NSW). Iron ore: Pilbara (WA). Solar: Bungala (SA), Gannawarra (VIC) — any reasonable example.
- Carbon dioxide (CO).
- Metals are not regrown like plants; they are extracted once, but they can be melted and used again many times.
Extraction and production
- Coal: open-cut or underground mining. Iron ore: open-cut mining. Natural gas: drilling (onshore or offshore).
- Benefit: large energy output with very low CO emissions at the power plant. Risk: radioactive waste lasting thousands of years (or: rare but severe accident risk).
- Their output depends on weather (wind speed, sunlight), so production changes through the day and year and cannot be dialled up on demand.
- Water held in a high dam flows down through turbines. The moving water spins the turbines, which turn generators to produce electricity.
- Any two of: habitat destruction, dust pollution, water pollution, visual impact, disturbed wildlife.
Explain and evaluate
- Fossil fuels take hundreds of millions of years to form from buried organic matter. We use them far faster than they are replaced, so on any human timescale the total amount is effectively fixed.
- Partly true: nuclear produces almost no CO or smoke during power generation. But it does create radioactive waste that stays hazardous for thousands of years, and uranium mining has its own environmental impacts. “Clean” is more complicated than “no smoke”.
- Replanting keeps the total forest biomass growing, so future timber supply is maintained, and keeps the forest’s role in absorbing CO, protecting soil, and sheltering wildlife.
- Coal: high CO, cheap fuel, very reliable. Solar: zero CO at the plant, free fuel, variable (depends on sun).
Applied contexts
- On paper yes: 7000 kWh produced vs 6500 kWh used. But production is highest in the day and lowest at night, while the family also uses power at night. Storage (battery) or feeding excess into the grid is needed to match supply to demand.
- Any two of: river pollution from dust or runoff; habitat loss along the river; noise and vibration; water use for processing; impact on fish and riverside vegetation.
- Any three of: What is the cost? What are the lifetime CO emissions? How reliable is the power? What jobs does each option provide? What is the visual/noise impact? How do we dispose of waste?
- Making new aluminium from bauxite takes large amounts of energy and mining. Recycling cans lets the aluminium re-enter the supply chain using far less energy and no new mining — closing the loop on an otherwise finite resource.
Challenge
- Example policies: (i) subsidies for rooftop solar — cost to taxpayers; (ii) retire coal plants early — risk of blackouts unless storage/gas cover the gap; (iii) mandate renewables in new builds — increases up-front cost of housing. Any reasonable suggestions with a real trade-off accepted.
- Pumping water faster than rain recharges lowers the water table permanently, can cause the ground to sink (subsidence), and lets salty water intrude into coastal aquifers. The damage may be impossible to reverse even if rainfall continues.
- Manufacturing an electric car creates more emissions than making a petrol car, mainly because of the battery. Ignoring manufacturing makes the EV look better than it really is. A full lifecycle shows EVs are still lower over their lifetime, but the gap is smaller than running-emissions alone suggest.
- Uranium is spread through the crust, but extracting it economically only works in rare concentrated ores. Those ores cannot regrow within a human timescale, so they run out, and replacing them with lower-grade sources becomes increasingly costly and energy-intensive.