Nonrenewable Energy & Fossil Fuels · Grade 12 Science
Chapter: Energy, Water & Material ResourcesNonrenewable Energy & Fossil Fuels
Learning goals
- I can describe how coal, oil, and natural gas form and how they are extracted.
- I can explain the environmental and climate consequences of burning fossil fuels.
- I can compare the benefits and drawbacks of nuclear power against those of fossil fuels.
Readings for this unit
Before this unit
Chemical/nuclear energy and electricity generation.
Use the detailed parent plan: two core 50–60-minute sessions per focused unit, with a third assigned for selected calculation/modeling topics. First study the core explanation and Parts 1–2 with their figures/checks; next study Parts 3–4, the whole-unit application, worked cases, varied practice and exit check. Attempt reasoning before opening guidance. Extend time when actual understanding requires it; investigations and chapter assessments have separate sessions.
Start with something to explain
Why is a fuel’s name insufficient to judge its full impact?
Illustrative evidence case. Combustion, extraction, leakage and conversion differ across supply chains.
Notice and wonder
Record two observations using the stated quantities or relationships. Keep observations separate from possible causes. Write one question that a new measurement could help answer.
Why is a fuel’s name insufficient to judge its full impact?
Your first model
Define delivered service and trace the complete selected boundary.
Build the language from the idea
- fossil fuel
- A nonrenewable energy resource — coal, oil, or natural gas — formed from the buried remains of ancient organisms transformed by heat and pressure over millions of years.
- combustion
- The chemical reaction of burning a fuel with oxygen, releasing the fuel's stored chemical energy as heat and light and producing carbon dioxide and other emissions.
- hydraulic fracturing (fracking)
- A drilling method that injects high-pressure fluid underground to crack open shale rock and release the oil or natural gas trapped inside it.
- nuclear fission
- The splitting of a heavy atomic nucleus (such as uranium-235) into smaller nuclei, releasing a large amount of energy that a power plant uses to make steam and generate electricity.
Coal, petroleum, natural gas, and mined nuclear fuels are treated as nonrenewable on human planning timescales. Fossil fuels store chemical energy in carbon-containing material formed over geological time. Nuclear fuels release energy by changes in nuclei; they are not fossil fuels.
Burning fossil fuels produces heat that may drive a turbine and generator or provide direct heating. Combustion emissions include CO₂ and may include particles, nitrogen oxides, and sulfur compounds depending on fuel and controls. Energy density, infrastructure, and operating flexibility influence use.
Fossil-fuel formation depends on organic source, burial history, heat, time, and geology. Coal often develops from plant-rich deposits; petroleum and gas have varied source and maturation pathways. Depth alone is not a sufficient universal predictor of oil versus gas.
Nuclear fission can supply heat for a turbine without direct CO₂ from carbon combustion. Mining, fuel processing, construction, and decommissioning still have life-cycle impacts; nuclear is not literally carbon-free across every boundary. Radioactive waste and long-term management require separate accounting.
Compare equal delivered energy with stated emission factors. If a supplied model uses coal 2.2lbCO₂/kWh and gas.9lbCO₂/kWh, replacing 1000 kWh gives a modeled reduction 1300lb. Those are practice factors, not universal current plant values or a full life-cycle comparison.
A resource decision should consider reliability, extraction impacts, climate emissions, other pollution, water use, cost, waste, and affected communities. Distinguish established mechanisms from locally variable numerical assumptions and do not choose solely from one bar-chart value.
Model check: Low direct operational CO₂ does not mean zero life-cycle impacts.
Build your understanding
Use the detailed parent plan: two core 50–60-minute sessions per focused unit, with a third assigned for selected calculation/modeling topics. First study the core explanation and Parts 1–2 with their figures/checks; next study Parts 3–4, the whole-unit application, worked cases, varied practice and exit check. Attempt reasoning before opening guidance. Extend time when actual understanding requires it; investigations and chapter assessments have separate sessions.
Part 1 · Distinguish a geological stock from its use rate
Fossil fuels are carbon-rich geological resources formed from ancient organic material under specific conditions. They are nonrenewable on human-use timescales because extraction can greatly exceed replacement. A resource estimate concerns potentially available material, while a reserve is the portion recoverable under stated technical/economic conditions. A rising reserve estimate does not mean new fuel formed that year. Separate a physical stock, an extraction flow and an economically defined category.
Read the visual model
Identify the labeled structures and units, then trace the arrows or compare values under the caption’s stated conditions. Separate the displayed evidence from a further inference. Write your reasoning before opening the guidance.
Can improved extraction technology increase reported reserves without rapid natural formation?
Visual reasoning — after your attempt
Yes. More of the existing resource may become recoverable under the changed conditions.
Coal, oil, and natural gas store chemical energy in materials formed through long geological processes. Nonrenewable means replacement is not comparable to human use on the relevant timescale, not that a precise exhaustion date follows from one current number. Reserves also depend on technical and economic definitions.
An inventory divided by annual use gives a simplified ratio, not a forecast accounting for changed demand, discovery, or accessible supply.
Pause and explain
Why is a reserve-to-use ratio not a fixed countdown?
Check your reasoning after answering
Both the measured recoverable stock and future extraction rate can change; the ratio assumes conditions remain constant.
Part 2 · Keep chemical input and useful output separate
Combustion transfers chemical energy into thermal and other forms; a generator delivers only a fraction as electricity. Conversion efficiency is useful output divided by fuel input within a defined boundary. Comparing emissions per megajoule of fuel with emissions per kilowatt-hour of delivered electricity mixes denominators unless efficiency is included. Natural gas often has lower direct combustion CO₂ per fuel energy than coal, but methane leakage and full life-cycle processes require additional accounting.
Read the visual model
Identify the labeled structures and units, then trace the arrows or compare values under the caption’s stated conditions. Separate the displayed evidence from a further inference. Write your reasoning before opening the guidance.
If1000 MJ input yields 380 MJ electricity, how much input is needed for 760 MJ electricity at the same efficiency?
Visual reasoning — after your attempt
2000 MJ under the same operating model.
Combustion converts an energy account into thermal transfers, and engines or generators deliver only a fraction as useful output. Efficiency depends on the stated device, service, and boundary. Electrical generation and delivered electricity can require additional transmission and distribution accounts.
A fuel delivering 24 MJ chemical input with 8 MJ useful electrical output has a one-third efficiency at that chosen boundary.
Pause and explain
What does a stated conversion efficiency compare?
Check your reasoning after answering
It compares a specifically defined useful output with a compatible input over the same process or interval.
Part 3 · Track extraction and emissions across the chain
A fuel life cycle includes extraction, processing, transport, conversion and residual management. Direct CO₂, methane leakage, particulates, sulfur compounds and land/water effects are different pathways that need separate evidence. “Cleaner” is incomplete without naming the pollutant, service and boundary. A climate comparison using CO₂-equivalent values also needs a stated time horizon and conversion method; it is not simply a count of molecules emitted.
Read the visual model
Identify the labeled structures and units, then trace the arrows or compare values under the caption’s stated conditions. Separate the displayed evidence from a further inference. Write your reasoning before opening the guidance.
Why can a lower combustion CO₂ factor be insufficient for a full climate ranking?
Visual reasoning — after your attempt
Upstream methane, conversion efficiency and other life-cycle emissions can change the result under the stated horizon/boundary.
Extraction, processing, transport, and use can produce different environmental effects. Combustion carbon dioxide is distinct from upstream leakage or other pollutants. Compare equivalent delivered service and consistent boundaries rather than ranking fuels from one isolated stage.
A fuel with lower emissions at combustion may still have important upstream effects. Those need measured quantities rather than an assumed zero.
Pause and explain
Why can a combustion-only comparison be incomplete?
Check your reasoning after answering
It excludes extraction, processing, transport, leakage, and infrastructure effects that may contribute within a wider assessment boundary.
Part 4 · Evaluate decisions with constraints and uncertainty
A transparent decision names criteria for judging options and constraints that must be met. Evidence can estimate emissions, reliability or cost under stated assumptions, while people can reasonably weight affordability, health, habitat or distribution differently. Report uncertainty and who bears each effect rather than hiding a value choice inside a technical score. Compare options delivering the same service and test whether the ranking changes when key assumptions change.
Read the visual model
Identify the labeled structures and units, then trace the arrows or compare values under the caption’s stated conditions. Separate the displayed evidence from a further inference. Write your reasoning before opening the guidance.
What would make a weighted score misleading?
Visual reasoning — after your attempt
Unstated weights, incomparable service units, omitted groups or uncertainty large enough to change the ranking.
An energy-system decision involves reliability, infrastructure, output, environmental effects, and costs measured over an appropriate interval. Separate scientific quantities from chosen priorities. A single efficiency value cannot establish the preferred choice for every site or policy.
Compare emissions per delivered kWh rather than total emissions from unequal service, then report uncertainty and omitted stages.
Pause and explain
What makes two fuel-system comparisons compatible?
Check your reasoning after answering
Their useful service, units, operating conditions, lifecycle boundary, and treatment of missing data must be comparable.
Apply the whole unit · Compare chemical input and useful service
Illustrative system A receives 24 MJ fuel energy and delivers 8 MJ electricity; system B receives 20 MJ and delivers 8 MJ. Supplied combustion emissions are 2.4 kg and 1.8 kg CO₂ respectively; upstream stages are excluded.
Your task
Calculate efficiencies and emissions per delivered MJ, compare the defined outcomes, and explain why the data cannot settle a full lifecycle or resource-policy decision.
What your response should show
- Define the system, quantities, units, and relevant conditions before selecting a model.
- Show intermediate calculations or a labeled evidence account, including signs or denominators.
- Explain how the supplied evidence supports the conclusion rather than reporting only an answer.
- Identify a meaningful uncertainty, model limit, or measurement needed to test the conclusion.
Response guidance — after your attempt
A efficiency=8/24=33.3%; B efficiency=8/20=40.0%.
A combustion intensity=2.4/8=0.300 kg CO₂/MJ; B=1.8/8=0.225 kg CO₂/MJ.
B uses less input and has 25% lower combustion intensity for this supplied equal output.
The conclusion is limited to the stated operating and combustion boundary. Upstream leakage, extraction impacts, useful-service timing, infrastructure, and other emissions remain unmeasured. The residual input energy needs a transfer or store account rather than being described as destroyed.
Scientific references and source-model foundations
Parent / teacher teaching notes
Ask which emissions stages the data include and keep stock availability distinct from conversion efficiency. Require an equal-service denominator. Ask the learner to explain each symbol, axis, unit and arrow before calculating. Calculated examples, supplied illustrative records and actual historical observations are labeled separately. Selected public OpenSciEd middle-school source figures are foundation examples, not complete high-school editions or an endorsement; all advanced explanations are supplied locally.
The key idea
Fossil and nuclear resources provide energy through different mechanisms; compare direct-operation emissions, life-cycle impacts, reliability, extraction, and waste separately.
CO2 Avoided by Switching Fuels
CO2 avoided = electricity (kWh) x (emission factor of old fuel - emission factor of new fuel)
the emission factor is the pounds of CO2 released per kWh for each fuel (for example, coal is about 2.2 lb/kWh and natural gas about 0.9 lb/kWh); the difference times the electricity generated gives the CO2 saved by switching.
Worked examples
Example 1
- Find the coal plant's yearly CO2: 500,000,000 kWh x 2.2 lb/kWh = 1,100,000,000 lb.
- Find the natural gas plant's yearly CO2: 500,000,000 kWh x 0.9 lb/kWh = 450,000,000 lb.
- Subtract to find what is avoided: 1,100,000,000 - 450,000,000 = 650,000,000 lb.
- So switching cuts CO2 by about 650 million pounds per year — though remember methane leaks from the gas supply chain can eat into that gain.
Example 2 · Worked application
- Efficiency=35/100×100%=35%.
- Remaining energy=65 MJ.
- It transfers mainly to thermal and other outputs rather than disappearing.
Compare energy at the same system boundary.
Example 3
- Identify the relevant quantities or mechanism.
- Both commonly make heat to drive a turbine; fossil fuels oxidize carbon compounds, while nuclear fission changes nuclei.
- State the model and conditions.
Example 4 · Find and fix the mistake
- Test the claim against the stated conditions: Compare energy at the same system boundary.
- Extraction, emissions, use efficiency and other effects matter alongside energy density.
Compare energy at the same system boundary.
Example 5 · Reason from the visual model
- A fuel life cycle includes extraction, processing, transport, conversion and residual management. Direct CO₂, methane leakage, particulates, sulfur compounds and land/water effects are different pathways that need separate evidence. “Cleaner” is incomplete without naming the pollutant, service and boundary. A climate comparison using CO₂-equivalent values also needs a stated time horizon and conversion method; it is not simply a count of molecules emitted.
- Upstream methane, conversion efficiency and other life-cycle emissions can change the result under the stated horizon/boundary.
Original pathway inventory; no current plant emission factor or universal fuel ranking is asserted.
Avoid these mistakes
- Low direct operational CO₂ does not mean zero life-cycle impacts.
Check your understanding
Compare fossil-fuel and nuclear electricity mechanisms.
Discuss the answer
Both commonly make heat to drive a turbine; fossil fuels oxidize carbon compounds, while nuclear fission changes nuclei.
Return to the phenomenon
Return to the initial case. Why is a fuel’s name insufficient to judge its full impact? Revise your drawing or explanation using two named ideas and one stated limitation.
Compare explanations after your attempt
Direct emissions and full life-cycle outcomes use different accounts; decisions also involve explicit constraints and priorities.
What should we investigate next?
Which comparison would test a remaining uncertainty? State what you would change, keep comparable and measure.
Investigate, calculate and revise
Keep a first model and an evidence-supported revision. Attempt each task before opening guidance; all required explanations and supplied-data routes are available locally.
Activity 1 · Return to the opening case
Use the opening phenomenon, unit definitions and explained Parts 1–4.
Your task
Return to the initial case. Why is a fuel’s name insufficient to judge its full impact? Revise your drawing or explanation using two named ideas and one stated limitation.
Success criteria
- Use the stated observations and appropriate units.
- Connect a labeled model with the physical/environmental mechanism.
- State assumptions and an evidence limitation.
- Explain a substantive revision or next test.
Hint
Keep object/material identity, material transfer and energy account distinct.
Response guidance — discuss after your attempt
Direct emissions and full life-cycle outcomes use different accounts; decisions also involve explicit constraints and priorities.
Activity 2 · Transfer to a changed case
Cover the worked answer and use the explained models, relationships and notebook.
Your task
Plant A delivers 40 MJ electricity from 100 MJ fuel; B delivers 50 MJ from 100 MJ. Direct fuel factors are 80 and 70 g CO₂/MJ input. Compare direct emissions per delivered MJ, then name an omitted term.
Success criteria
- Use the stated measurements or conditions, with correct units.
- Connect the result to the physical or environmental mechanism or evidence relationship.
- Identify the assumption, model limit or further evidence requested.
Hint
Name known quantities and conditions, show intermediate steps and check conservation.
Response guidance — discuss after your attempt
A:8000/40=200 g/MJ delivered. B:7000/50=140 g/MJ. Upstream leakage, transport or construction is omitted; this direct comparison is not a complete life-cycle ranking.
Words to know
- fossil fuel
- A nonrenewable energy resource — coal, oil, or natural gas — formed from the buried remains of ancient organisms transformed by heat and pressure over millions of years.
- combustion
- The chemical reaction of burning a fuel with oxygen, releasing the fuel's stored chemical energy as heat and light and producing carbon dioxide and other emissions.
- hydraulic fracturing (fracking)
- A drilling method that injects high-pressure fluid underground to crack open shale rock and release the oil or natural gas trapped inside it.
- nuclear fission
- The splitting of a heavy atomic nucleus (such as uranium-235) into smaller nuclei, releasing a large amount of energy that a power plant uses to make steam and generate electricity.
In the real world
Compare supplied direct-operation and life-cycle factors separately when evaluating equal delivered energy.
Exit check
Compare fossil-fuel and nuclear electricity mechanisms.
Check your explanation after answering
Both commonly make heat to drive a turbine; fossil fuels oxidize carbon compounds, while nuclear fission changes nuclei.
Explain your reasoning without notes. If a key idea is missing, revisit the lesson and try again.