Study Companion
Topic 05 | Earth and space sciences

Earth's resources - renewable & non-renewable

Year 8 (Levels 7-8 band): classifying Earth's resources as renewable or non-renewable, the processes of extraction and energy production, and weighing sustainability trade-offs.

45-60 min Printable practice Answer key Challenge included
VC2S8U09
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What you will learn

Worked example 0 Real-world example: the family home

A household gets its hot water from a gas heater, its electricity from the grid (mostly coal in Victoria), and its cooking gas from natural gas. Classify each energy source and suggest one renewable replacement for each.

  1. Gas hot water: natural gas — non-renewable fossil fuel. Replace with a solar hot-water system or a heat pump powered by renewable electricity.
  2. Grid electricity from coal: non-renewable. Replace with solar PV on the roof or a green-power plan (wind/solar from the grid).
  3. Gas cooking: non-renewable. Replace with an electric induction cooktop powered by renewable electricity.

Key idea: any fossil fuel is non-renewable on human timescales because it takes millions of years to form.

1. Renewable vs non-renewable

A renewable resource replenishes quickly enough (at human timescales) to keep up with use, if we manage it well.

A non-renewable resource exists in a fixed or very slowly replenished amount. Once used, it is effectively gone.

2. How resources are extracted

Different resources need different extraction methods. Each involves benefits (useful material) and risks (environmental cost).

ResourceExtraction methodExample locationMain risk
CoalOpen-cut or underground miningLatrobe Valley (VIC), Hunter Valley (NSW)CO2_2 emissions, habitat loss
Iron oreOpen-cut miningPilbara (WA)Dust, landscape destruction
Natural gasDrilling (onshore or offshore)Bass Strait (VIC)Methane leaks, ocean pollution
UraniumHard-rock or in-situ leachingOlympic Dam (SA)Radioactive waste
TimberLoggingTasmania, Victorian Central HighlandsDeforestation, biodiversity loss
Wind energyWind turbinesMacarthur Wind Farm (VIC)Visual impact, some bird strikes
Solar energySolar PV panelsRooftops, Bungala (SA) solar farmLand use, panel disposal

3. Energy production: benefits and risks

Coal-fired power

Natural gas

Nuclear

Solar / Wind

Hydroelectric

Worked example 1 Comparing choices

A new power station is planned. Option A is a coal plant; option B is a solar farm with battery storage. List two advantages and two disadvantages of each.

  1. Option A (coal). Advantages: delivers power day and night; uses established technology. Disadvantages: high CO2_2 emissions; coal runs out; air pollution.
  2. Option B (solar + battery). Advantages: no emissions during operation; fuel (sunlight) is free. Disadvantages: depends on sunny weather; batteries and panels need minerals that are mined.

Key idea: “best” is rarely one-sided. Decisions trade off climate impact, cost, reliability, and land use.

4. Sustainability

Sustainability means meeting today’s needs without preventing future generations from meeting theirs.

Three key ideas:

  1. Rate of use ≤\leq rate of renewal (for renewable resources).
  2. Reduce, reuse, recycle to stretch non-renewable resources.
  3. Replace high-impact resources with lower-impact alternatives wherever possible.
Worked example 2 A sustainability audit

A school uses 30 000 kWh of electricity from coal-based grid power and throws away 2 tonnes of paper per year. Suggest three sustainability improvements and justify each.

  1. Install rooftop solar to replace a share of grid electricity — reduces fossil fuel use and bills.
  2. Set printers to double-sided by default — roughly halves paper use (reduce).
  3. Run a paper-recycling program — paper becomes pulp for new paper, cutting new-tree demand.

Key idea: sustainability is usually achieved by many small changes that add up, not one big fix.

5. Recycling and the circular economy

Metals such as aluminium and copper can be melted down and reused indefinitely. Recycling aluminium uses about 5% of the energy needed to make it from bauxite ore. A circular economy tries to keep materials in use rather than sending them to landfill, effectively turning non-renewable materials into much longer-lasting resources.

Worked example 3 Energy saved by recycling

Making aluminium from ore uses about 200200 MJ per kg. Recycling uses about 1010 MJ per kg. Estimate the energy saved per kilogram recycled, and the percentage saving.

  1. Energy saved =200−10=190= 200 - 10 = 190 MJ/kg.
  2. Percentage saving =190200×100%=95%= \dfrac{190}{200} \times 100\% = 95\%.
  3. Recycling aluminium saves roughly 95%95\% of the energy compared with making it new.

Practice: Year 8

Fluency

Classifying resources

    1. Classify each as renewable or non-renewable: (a) wind, (b) coal, (c) uranium, (d) solar, (e) timber (managed forest), (f) natural gas.
    2. Name two fossil fuels.
    3. Give an Australian example of a coal mine, an iron-ore mine, and a solar farm.
    4. What is the main greenhouse gas released by burning fossil fuels?
    5. Why are metals sometimes called “recyclable” rather than renewable?
Fluency

Extraction and production

    1. What method is used to extract coal? Iron ore? Natural gas?
    2. State one benefit and one risk of nuclear power.
    3. Why are wind and solar described as variable energy sources?
    4. Explain how a hydroelectric dam generates electricity.
    5. List two environmental risks of open-cut mining.
Reasoning

Explain and evaluate

    1. Explain why fossil fuels are classed as non-renewable even though new oil is still occasionally discovered.
    2. A politician says “nuclear is clean because there is no smoke.” Evaluate this claim.
    3. Describe two reasons replanting trees after logging is important for sustainability.
    4. Compare coal and solar on three criteria: CO2_2 emissions, fuel cost, and reliability.
Problem solving

Applied contexts

    1. A family uses 6500 kWh of electricity per year. A 5 kW rooftop solar system produces about 7000 kWh per year in Victoria. Would this cover their usage? What other factor matters?
    2. A mining company wants to open an iron-ore mine next to a river. List two environmental impacts they should plan to manage.
    3. A community is choosing between adding a new coal generator or a wind farm. Suggest three questions the community should ask before deciding.
    4. Explain, using the idea of a circular economy, why placing aluminium cans in the yellow bin reduces demand for bauxite mining.

Challenge

Reasoning

Harder reasoning

    1. A country’s electricity mix is 70%70\% coal, 20%20\% gas, 10%10\% renewables. A new target is 50%50\% renewables within 10 years. Suggest three policies that would help reach this target and predict one challenge each might create.
    2. Groundwater is a renewable resource, but only if used sustainably. Explain why overuse can cause permanent damage to an aquifer even if some rain still recharges it.
    3. A lifecycle assessment of a product tracks its impacts from raw-material extraction to disposal. Explain why comparing only “running” emissions of two cars (e.g. petrol vs electric) can be misleading.
    4. “Non-renewable” is defined relative to a human timescale. Use this idea to explain why uranium, which is found in tiny amounts throughout Earth’s crust, is still called non-renewable.
Answers

Answer key

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Year 8 answers

Fluency

Classifying resources

    1. (a) Renewable, (b) non-renewable, (c) non-renewable, (d) renewable, (e) renewable (managed), (f) non-renewable.
    2. Any two of: coal, oil, natural gas.
    3. Coal: Latrobe Valley (VIC) or Hunter Valley (NSW). Iron ore: Pilbara (WA). Solar: Bungala (SA), Gannawarra (VIC) — any reasonable example.
    4. Carbon dioxide (CO2_2).
    5. Metals are not regrown like plants; they are extracted once, but they can be melted and used again many times.
Fluency

Extraction and production

    1. Coal: open-cut or underground mining. Iron ore: open-cut mining. Natural gas: drilling (onshore or offshore).
    2. Benefit: large energy output with very low CO2_2 emissions at the power plant. Risk: radioactive waste lasting thousands of years (or: rare but severe accident risk).
    3. Their output depends on weather (wind speed, sunlight), so production changes through the day and year and cannot be dialled up on demand.
    4. Water held in a high dam flows down through turbines. The moving water spins the turbines, which turn generators to produce electricity.
    5. Any two of: habitat destruction, dust pollution, water pollution, visual impact, disturbed wildlife.
Reasoning

Explain and evaluate

    1. 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.
    2. Partly true: nuclear produces almost no CO2_2 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”.
    3. Replanting keeps the total forest biomass growing, so future timber supply is maintained, and keeps the forest’s role in absorbing CO2_2, protecting soil, and sheltering wildlife.
    4. Coal: high CO2_2, cheap fuel, very reliable. Solar: zero CO2_2 at the plant, free fuel, variable (depends on sun).
Problem solving

Applied contexts

    1. 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.
    2. 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.
    3. Any three of: What is the cost? What are the lifetime CO2_2 emissions? How reliable is the power? What jobs does each option provide? What is the visual/noise impact? How do we dispose of waste?
    4. 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.
Reasoning

Challenge

    1. 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.
    2. 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.
    3. 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.
    4. 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.

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