Science — Natural Resources — CTET Mathematics & Science

Six NCERT chapters feed into this one CTET sub-topic — Class VII's "Water: A Precious Resource" and "Forests: Our Lifeline" and "Soil," Class VIII's "Coal and Petroleum," "Combustion and Flame," and "Pollution of Air and Water" — but at weightPct: 4, this is one of the lightest of the eight Science chapters, guaranteed only about 2 questions out of Science's 30. That mismatch between content breadth and mark weight is exactly what should shape your prep: this is a recognise-and-recall chapter, not a deep-dive one, and the two questions it actually delivers could come from any of the six themes below almost at random.

1. What CTET actually asks

Natural Resources carries weightPct: 4 of the Mathematics & Science elective's 60 questions — roughly 2 of the Science sub-area's ~30 questions, or 2 of the exam's 150 total marks. Every CTET question is marked +1 for correct, 0 for wrong or unattempted — there is no negative marking anywhere on the paper, so a question from this chapter is never worth skipping over a reasoned guess.

Six themes share this small mark budget, and in a typical year only one or two of them actually surface as a question — you don't get a question from every theme, you get roughly two questions drawn from among all six:

1. Air — composition, air pollution, and why combustion and respiration both depend on it.
2. Water — sources, the water cycle, water pollution, conservation, and groundwater depletion.
3. Forests as a resource — ecosystem services, deforestation, and conservation.
4. Soil — formation, profile, types, erosion, and conservation.
5. Coal and petroleum — fossil-fuel formation, products, conservation, and renewable alternatives.
6. Combustion and flame — types of combustion, the structure of a flame, fuel efficiency, and fire safety.

CTET's questions on this chapter fall into two recognisable shapes. Direct-fact questions name a component, process, or figure outright — "What percentage of air is nitrogen?" Applied/scenario questions describe a household or classroom situation and ask which principle it illustrates — "Why should water, not carbon dioxide, never be used on an electrical fire?" Because the mark weight is so small, the efficient strategy here is genuinely breadth over depth: know each of the six themes' core facts at NCERT Class VII-VIII level, well enough to answer whichever one or two happen to appear, rather than mastering any single theme in isolation.

2. Air — composition, pollution, and the need for oxygen

Air is a mixture, not a single substance — by volume, dry air is roughly 78% nitrogen, 21% oxygen, and about 1% other gases (argon, carbon dioxide, water vapour, and suspended dust), a composition CTET tests as a direct-recall fact more often than any other single number in this chapter.

Two everyday processes both depend on that 21% oxygen slice, and CTET likes pairing them in the same question: combustion (burning) is a chemical reaction between a fuel and oxygen that releases heat and light — cover a burning candle with a jar and it goes out once the trapped oxygen is used up, the same principle behind smothering a fire to starve it of air. Respiration is the process by which living cells break down food (glucose) using oxygen to release the energy the body runs on, producing carbon dioxide and water as by-products — which is why both plants and animals need a continuous air supply, not just animals.

Air pollution is the presence of harmful substances in air at concentrations that damage health or the environment. The named pollutants CTET tests by name: suspended particulate matter (SPM) — soot, dust, smoke; sulphur dioxide (SO₂) and oxides of nitrogen (NOₓ) — from burning fossil fuels, which dissolve in rainwater to form acid rain, damaging monuments (the Taj Mahal is the standard NCERT example), crops, and aquatic life; carbon monoxide (CO) — a poisonous, colourless, odourless gas produced by incomplete combustion, dangerous in poorly ventilated rooms with a burning heater or geyser; excess carbon dioxide (CO₂) — a greenhouse gas driving global warming; and chlorofluorocarbons (CFCs), once common in refrigerants and aerosols, which deplete the ozone layer and increase the ultraviolet radiation reaching the ground. The chief sources across all of these are the same short list — vehicle exhaust, industrial smoke, burning of fossil fuels and biomass, and deforestation (which removes the trees that would otherwise absorb CO₂).

3. Water — sources, the water cycle, pollution, and conservation

Water reaches us from two broad sources: surface water — rivers, lakes, ponds, and (saline, not directly potable) seas — and groundwater, rainwater that percolates through soil and rock to collect in underground layers called aquifers, drawn up through wells, tube wells, hand pumps, or reaching the surface naturally as springs.

The water cycle is the continuous movement of water between the earth's surface and the atmosphere: the sun's heat causes evaporation from oceans, rivers and lakes, and transpiration releases water vapour from plants; the rising vapour cools and condenses into clouds; clouds release water back down as precipitation (rain, snow, or hail); and the fallen water either runs off into rivers and water bodies or infiltrates the ground to recharge aquifers, closing the loop.

Water pollution comes chiefly from four sources CTET expects you to name: untreated domestic sewage; industrial effluents carrying chemicals and heavy metals; agricultural runoff, where excess fertiliser triggers eutrophication (a nutrient-fuelled algal bloom that depletes dissolved oxygen and kills fish) and pesticide residue enters the food chain; and oil spills or direct dumping of waste into water bodies. The human cost is chiefly waterborne disease — cholera, typhoid, and diarrhoea are the standard NCERT examples of illnesses spread by contaminated drinking water.

Water conservation measures worth naming individually: rainwater harvesting (rooftop collection and recharge pits that return runoff to the aquifer instead of losing it to drains), drip and sprinkler irrigation in place of wasteful flood irrigation, fixing leaking taps and pipes, and treating and reusing wastewater rather than discharging it untreated.

Groundwater depletion is a distinct, increasingly-tested angle: water tables are falling in many parts of India chiefly because of over-extraction through tube wells for irrigation (intensified since the Green Revolution in states like Punjab and Haryana), reduced recharge as deforestation and urban concretisation seal off the surfaces rainwater would otherwise soak through, and increasingly erratic monsoon rainfall. The consequences compound: deeper and deeper borewells are needed to chase a falling water table, and in some regions this reaches aquifer layers contaminated with arsenic or fluoride. The fixes mirror the causes — mandatory rainwater harvesting structures, check dams and percolation tanks, community watershed management, and regulating how much groundwater can be pumped.

4. Forests as a resource

NCERT frames a forest not as a stockpile of timber but as a dynamic, living system — an interdependent web of plants, animals, microorganisms, and soil — and CTET's forest questions consistently test that ecosystem-services framing over a narrower "trees = wood" view.

The services a forest provides, beyond timber: oxygen production and carbon absorption through photosynthesis (forests act as a carbon sink); regulating local rainfall and climate, since transpiration returns significant moisture to the atmosphere; preventing soil erosion — root systems bind soil in place, and the canopy breaks the direct force of rainfall before it strikes the ground; maintaining the water table, since forest floors act like a sponge, slowing runoff and aiding groundwater recharge; sustaining biodiversity and habitat; and supplying non-timber forest produce (fruit, fodder, gums, resins, medicinal plants) that forest-dwelling and tribal communities depend on directly for livelihood.

Deforestation — the large-scale clearing of forest — is driven by agricultural expansion, logging, mining, dam and infrastructure projects, and fuelwood collection. Its effects cascade well beyond the missing trees: accelerated soil erosion and eventual desertification, a disrupted local water cycle and reduced rainfall, loss of biodiversity, rising atmospheric CO₂, and a higher risk of flooding and landslides, since there are no longer roots to hold soil and slow water. CTET's most common trap option on this theme understates deforestation's effect to "just" habitat loss for wildlife — the actual scope reaches soil, water, and climate together.

Conservation responses: afforestation and reforestation, social/community forestry and Joint Forest Management (JFM) programmes that give local communities a stake in protecting forest land, protected areas (national parks, wildlife sanctuaries, biosphere reserves), and sustainable, selective logging in place of clear-felling. The Chipko movement — villagers in the Himalayan foothills, prominently women, embracing trees to physically block felling in the 1970s — is the standard NCERT example of grassroots forest conservation and worth recognising by name.

5. Soil — formation, profile, types, and erosion

Soil formation is weathering of parent rock acting over an extremely long timescale — physical weathering (temperature swings, freeze-thaw cycling, and abrasion by wind and water), chemical weathering (rock minerals reacting with water, oxygen, and dissolved carbon dioxide), and biological weathering (plant roots prising rock apart, lichens and burrowing organisms breaking it down further). Because this process unfolds over centuries to millennia, soil is best treated as a slowly-renewing resource on any human timescale — a fact that connects directly to why soil erosion (Section 5.3) is such a serious concern: soil is lost far faster than it forms.

The soil profile is built of distinct layers, top to bottom:

Soil types, classified by particle composition: sandy soil (large particles, drains fast, retains little water, low fertility), clayey soil (fine, tightly packed particles, retains water well but drains and aerates poorly), and loamy soil — a balanced mix of sand, silt, and clay, and the type NCERT identifies as best suited to most agriculture, since it combines adequate drainage with good water retention and fertility.

Soil erosion is the removal of topsoil by wind or water, accelerated by deforestation, overgrazing, faulty agricultural practice (continuous monocropping without rotation), and construction. Its effects: loss of the fertile topsoil layer that took centuries to build, siltation that reduces the capacity of rivers and reservoirs, and, in severe cases, desertification. Conservation measures worth naming individually: afforestation, contour ploughing (ploughing along a slope's contour rather than up-and-down it, to slow runoff), terrace farming (cutting step-like terraces into hillsides, common across hilly regions), strip cropping, shelter belts (rows of trees planted to break wind speed, a standard practice in arid regions like Rajasthan), and crop rotation.

6. Coal and petroleum — fossil fuels and the case for renewables

Coal formed from the buried remains of ancient plant matter, and petroleum (crude oil, alongside natural gas) formed from the buried remains of marine organisms — in both cases, sediment burial subjected the remains to intense heat and pressure over millions of years, gradually converting them into today's carbon- and hydrocarbon-rich fuels. Coal formation, per the NCERT account, began roughly 300 million years ago. Because both formed once, over a geological timescale, and are being consumed at a rate that vastly outstrips any natural replenishment, coal and petroleum are classified as non-renewable resources — a classification about the mismatch between formation rate and consumption rate, not a claim that the underlying geological process has permanently stopped (see Section 8 for the exact misconception this invites).

Both fuels are refined into a range of everyday products. Heating coal in the absence of air (destructive distillation) yields coke (used in steelmaking), coal tar (a raw material for dyes, drugs, and synthetic materials), and coal gas. Fractional distillation of crude petroleum separates it into petroleum gas/LPG, petrol, kerosene, diesel, lubricating oil, paraffin wax, and bitumen — petroleum is often called "black gold" precisely because nearly every fraction serves a distinct use. Natural gas, frequently found alongside petroleum deposits, is compressed into CNG as a comparatively cleaner-burning vehicle fuel.

Conservation of fossil fuels in everyday terms: using public transport and carpooling, keeping vehicles well-maintained for efficient combustion, switching off engines rather than idling, and simply avoiding wasteful use. But conservation only slows depletion — it doesn't solve the underlying finite-supply problem, which is the case CTET expects you to connect to renewable alternatives: solar energy (photovoltaic cells, solar cookers and heaters), wind energy, hydro power, and biogas (from cattle dung and organic waste — the "gobar gas" plants common in rural India, which produce both fuel and manure as a by-product). These sources are inexhaustible on any human timescale and, in general, pollute far less than fossil fuels, whose combustion drives both global warming (via CO₂) and acid rain (via SOₓ and NOₓ) — the same pollution mechanism covered in Section 2.

7. Combustion and flame

Combustion is a chemical reaction in which a substance reacts with oxygen to release heat and, usually, light. It needs three things at once — fuel, oxygen, and a temperature at or above the fuel's ignition temperature (the lowest temperature at which it catches fire and keeps burning) — and removing any one of the three puts a fire out. That's why water works on an ordinary wood or paper fire (it cools the fuel below its ignition temperature) but must never be used on an oil fire (oil floats on water and spreads) or an electrical fire (water conducts electricity); carbon dioxide is used instead for both, since it smothers the fire by cutting off its oxygen supply and doesn't conduct electricity.

CTET distinguishes three types of combustion: rapid combustion, where a fuel burns quickly with a clearly visible flame and heat, as in a gas stove; spontaneous combustion, where a substance catches fire on its own, with no external flame or spark, under ordinary conditions — white phosphorus is the standard NCERT example, and is stored underwater precisely because it ignites spontaneously in open air; and explosion, a sudden reaction releasing a large burst of heat, light, gas, and sound in a very short time, as in a firecracker.

Only fuels that vaporise while burning produce a visible flame — a candle or an LPG stove does, but glowing charcoal, which doesn't vaporise, does not. A candle flame's classic three-zone structure is a favourite CTET diagram-recall question: the innermost dark zone holds unburnt wax vapour and is the coolest region; the middle luminous zone is where incomplete combustion (insufficient oxygen) leaves glowing, unburnt carbon particles, giving the flame its bright yellow colour; and the outer non-luminous zone, where combustion is complete, burns blue and is the hottest part of the flame — the zone a goldsmith holds metal in to melt it.

A fuel's calorific value — the heat released by completely burning a unit mass of it, measured in kJ/kg — is the standard measure of fuel efficiency. A good fuel combines a high calorific value with a moderate ignition temperature (low enough to ignite reliably, high enough to store and handle safely), minimal smoke or harmful residue, and ready availability at reasonable cost. Fire safety follows directly from the fire triangle: keep inflammable substances away from open flame, never use water on an oil or electrical fire, and ensure adequate ventilation wherever a fuel is burning indoors, since incomplete combustion in a closed room produces dangerous levels of carbon monoxide.

8. Teaching natural resources — activities and common misconceptions

NCERT's preferred approach to this entire theme is experiential, not textbook-first — a stance that previews the "process validity" and "connecting to the child's lived environment" criteria formalised in the next chapter. A working teacher is expected to reach for hands-on classroom and school-level projects rather than lecture through each theme: building a simple rainwater-harvesting model from a funnel, bottle, and pipe to demonstrate collection and recharge; testing local soil samples by shaking them with water in a jar and observing how sand, silt, and clay settle into visibly distinct layers by particle size; setting up a school composting or vermicomposting pit from kitchen and garden waste, connecting the abstract idea of humus formation to something students can watch happen; running a school water audit to find and fix leaking taps; and maintaining a small school nursery or tree-plantation drive that gives afforestation a concrete, ongoing classroom presence rather than a one-line textbook fact.

A handful of misconceptions recur often enough in CTET's option-writing to name individually. The most consequential: students (and sometimes teachers) reason that coal and petroleum are "renewable, if we just wait long enough," since more will technically form given enough geological time. The reasoning isn't wrong about geology — it's wrong about scale: renewability, as a practical classroom concept, means replenishment within a timescale relevant to human use, and millions of years is many orders of magnitude beyond that, which is exactly why these fuels are still correctly classified as non-renewable. A second common error treats soil formation and soil erosion as roughly balanced, ongoing processes — they are not: formation takes centuries, while a single severe monsoon or a few seasons of poor farming practice can strip away a comparable depth of topsoil, which is precisely why erosion is treated as a serious, not a self-correcting, problem. A third: treating air as a single gas rather than a mixture, and a fourth: assuming Earth's "71% water" figure means water is abundantly available for use, when in fact only a small fraction of that total is fresh water accessible for drinking, farming, and industry, most of it stored in glaciers, ice caps, and deep groundwater.

10. Common traps

• Treating air as a single gas rather than a mixture — always frame it as roughly 78% nitrogen, 21% oxygen, and about 1% other gases, not one dominant substance.
• "Coal and petroleum will become renewable eventually" — technically true of the geology, practically false as a classroom classification: replenishment on a scale of millions of years is not renewable on any human-relevant timescale.
• Confusing soil formation with soil erosion as opposing, self-balancing processes — formation is slow (centuries), erosion can be fast (a single severe monsoon), which is exactly why erosion outpaces formation and needs active conservation.
• Assuming deforestation's damage is limited to wildlife habitat loss — its effects extend to soil erosion, disrupted rainfall and the water cycle, and rising atmospheric CO₂.
• Using water to fight an oil or electrical fire — water spreads oil fires and conducts electricity; carbon dioxide is the correct choice for both, since it smothers the fire by cutting off oxygen without conducting current.
• Believing combustion always needs an external spark or flame to start — spontaneous combustion (white phosphorus in open air is the standard example) catches fire under ordinary conditions with no external ignition source at all.
• Assuming Earth's abundant total water supply means fresh water is abundant too — only a small fraction of Earth's water is usable fresh water; most of the rest is saline ocean water or locked in ice.

11. Revision protocol

Because this chapter's six themes share only about 2 guaranteed marks, prep should stay light-touch and broad rather than deep on any single theme: one clean fact-sheet per theme (air's composition and pollutants, water's cycle and conservation methods, forests' ecosystem services, soil's profile and erosion controls, fossil-fuel formation and its renewable alternatives, and the flame's three zones), reviewed on rotation. Fix the two facts CTET tests most reliably in this chapter — air's 78/21 composition, and the geological-timescale reasoning behind "non-renewable" — as instant recall, since they recur across multiple option-writing patterns even when the surface question changes. And because NCERT frames every one of these six themes through hands-on, experiential activities rather than pure textbook recall, keep the pedagogy angle in view alongside the content itself: a scenario question describing a classroom rainwater-harvesting model or a soil-testing activity is testing the same content knowledge, just dressed in NCERT's preferred activity-based framing.