← Engineering Chemistry & Environmental Science · DSSSB AE Civil

Chapter 4 of 8

Polymers & Nanomaterials

In the DSSSB AE Civil syllabus under Engineering Chemistry & Environmental Science · 2 parts

Fuels, Lubricants & Polymers · Nanomaterials & Environmental Chemistry

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📑 Contents (16 sections)

Part 1 of 2

Fuels, Lubricants & Polymers

Last reviewed 16 Sept 2026 · 12 min read

Fuels

A fuel is a combustible substance that releases heat energy on burning.

Classification

Origin	Solid	Liquid	Gaseous
Primary (natural)	Wood, peat, lignite, coal	Crude petroleum	Natural gas
Secondary (derived)	Charcoal, coke, briquettes	Petrol, diesel, kerosene, fuel oil, biodiesel, ethanol	Producer gas, water gas, coal gas, LPG, biogas, hydrogen

Characteristics of a good fuel

High calorific value; moderate ignition temperature; low moisture and ash; low sulphur and non-polluting combustion products; controllable combustion; easy storage, transport and handling; low cost and availability.

Calorific value

Calorific value (CV) — heat liberated by complete combustion of unit mass (or volume) of fuel.

Term	Meaning
Gross (higher) calorific value, HCV/GCV	Heat released when combustion products are cooled to room temperature — water vapour condensed, latent heat recovered
Net (lower) calorific value, LCV/NCV	Heat actually available when water vapour escapes — HCV minus latent heat of steam formed

FormulaCalorific value relations

Dulong's formula (HCV of coal from ultimate analysis, percentages):

HCV = \frac{1}{100} [8080 C + 34500 (H - \frac{O}{8}) + 2240 S] kcal/kg

Net calorific value:

LCV = HCV - 0.09 H \times 587 kcal/kg

(H in %; 587 kcal/kg ≈ latent heat of steam; 9 kg of water forms per kg of hydrogen.)

Bomb calorimeter (solids and liquids): $HCV = \frac{( W + w ) ( t _{2} - t _{1} )}{x}$ (with corrections), where W = water mass, w = water equivalent of calorimeter, x = mass of fuel. Junkers gas calorimeter — for gaseous fuels.

1 kcal ≈ 4.187 kJ.

Solid fuels — coal

Formation and rank

Plant matter → peat → lignite (brown coal) → sub-bituminous → bituminous → anthracite (coalification with increasing pressure, temperature and time).

With increasing rank: carbon content and calorific value increase; moisture and volatile matter decrease; ignition becomes more difficult (anthracite burns with little smoke).

Analysis of coal

Analysis	Determines	Significance
Proximate analysis	Moisture (at ~~105–110 °C), volatile matter (~~925 °C, covered crucible), ash (~700–750 °C, open), fixed carbon (by difference)	Practical assessment: high moisture and ash reduce CV; high volatile matter → long smoky flame; high fixed carbon → higher CV
Ultimate analysis	C, H, N, S, O (elemental)	Calorific value calculation (Dulong), combustion air, pollution (S)

Carbonisation

Heating coal in absence of air:

Low-temperature carbonisation (~500–700 °C) — semi-coke, domestic fuel.
High-temperature carbonisation (~900–1200 °C) — metallurgical coke (strong, porous, low sulphur) for blast furnaces; by-products coal gas, tar, ammonia (Otto–Hoffman by-product ovens).

Liquid fuels

Petroleum refining

Crude oil is separated by fractional distillation into fractions (approximate boiling ranges): LPG gases → petrol (gasoline) → naphtha → kerosene → diesel → fuel oils → lubricating oils, waxes → bitumen (residue — used in road construction). Cracking (thermal/catalytic) breaks heavy fractions into lighter, more valuable ones; reforming improves octane.

Knocking, octane and cetane numbers

Concept	Petrol (SI) engines	Diesel (CI) engines
Knocking	Premature auto-ignition of unburnt end gas → metallic knock, power loss, damage	Long ignition delay → accumulated fuel burns suddenly (diesel knock)
Rating	Octane number — % of iso-octane (ON = 100) in a mixture with n-heptane (ON = 0) that knocks like the fuel	Cetane number — % of cetane (n-hexadecane) (CN = 100) in mixture with α-methylnaphthalene (CN = 0)
Good fuel	High octane (branched chains, aromatics)	High cetane (straight-chain paraffins)
Additives	Anti-knock agents (earlier tetraethyl lead — phased out; now MTBE, ethanol)	Cetane improvers

Straight-chain hydrocarbons have low octane but high cetane — so a good petrol is a poor diesel and vice versa.

Alternative liquid fuels

Biodiesel — methyl esters from vegetable oils/animal fats by transesterification; renewable, biodegradable, lower sulphur.
Ethanol — from sugarcane molasses, grains; blended with petrol (ethanol blending programmes increase blend ratios over time).
Power alcohol, methanol.

Gaseous fuels

Fuel	Main constituents (approx.)	Features / uses
Natural gas	Mainly methane	High CV; piped gas, power plants, fertilisers
CNG	Compressed natural gas (methane) at high pressure	Cleaner vehicle fuel
LPG	Propane + butane (liquefied under pressure)	Domestic cooking, industry; heavier than air (leaks settle low); odorant added
Biogas	Methane (roughly 55–65%) + CO₂	Anaerobic digestion of cattle dung, sewage sludge, organic waste; manure by-product
Producer gas	CO + N₂ (+ H₂)	Air + steam over hot coke; low CV; furnaces
Water gas	CO + H₂	Steam over red-hot coke; higher CV
Coal gas	H₂, CH₄, CO	Carbonisation by-product
Hydrogen	H₂	Highest CV per unit mass, clean (water only); storage/safety challenges; green hydrogen from electrolysis using renewable power

Advantages of gaseous fuels: clean combustion, easy control, little excess air, no ash; disadvantages: storage and leakage hazards.

Combustion calculations

FormulaCombustion relations (by mass)

C + O₂ → CO₂ : 12 kg C needs 32 kg O₂ (→ 44 kg CO₂)
2H₂ + O₂ → 2H₂O : 4 kg H₂ needs 32 kg O₂ (1 kg H needs 8 kg O₂; forms 9 kg H₂O)
S + O₂ → SO₂ : 32 kg S needs 32 kg O₂

Minimum O₂ per kg fuel $= \frac{32}{12} C + 8 (H - \frac{O}{8}) + S$ (C, H, O, S as mass fractions) Air contains about 23% O₂ by mass (≈ 21% by volume):

Minimum air = \frac{O _{2} required}{0.23} kg

Actual air includes excess air for complete combustion.

Part 2 of 2

Nanomaterials & Environmental Chemistry

Last reviewed 16 Sept 2026 · 11 min read

Nanomaterials

Nanomaterials — materials with at least one dimension in the nanoscale (about 1–100 nm); 1 nm = 10⁻⁹ m (a human hair is roughly tens of thousands of nanometres wide).

Why nanoscale properties differ

Very high surface area to volume ratio — more atoms at the surface → higher reactivity, adsorption, catalytic activity.
Quantum confinement effects — changes in optical, electrical and magnetic properties (e.g. colour of gold nanoparticles, band gap of quantum dots).
Altered mechanical, thermal and melting behaviour.

FormulaSpecific surface area of spheres

S S A = \frac{6}{ρ d}

$ρ$ = density; $d$ = particle diameter — halving the size doubles the surface area.

Classification

Dimensions at nanoscale	Examples
0D (all three dimensions nanoscale)	Nanoparticles, quantum dots, fullerenes (C₆₀)
1D (two dimensions nanoscale)	Carbon nanotubes (CNTs), nanowires, nanorods, nanofibres
2D (one dimension nanoscale)	Graphene, nanosheets, thin films, nanoclays
3D nanostructured	Nanocomposites, nanoporous materials

Important nanomaterials

Material	Key properties	Uses
Carbon nanotubes (single/multi-walled)	Very high tensile strength and stiffness, electrical conductivity	Composites, sensors, self-sensing concrete (research)
Graphene (single layer of carbon atoms)	Extremely strong, highly conductive, impermeable	Coatings, electronics, cement composites (research)
Nano-silica (nano-SiO₂)	Highly pozzolanic, filler effect	Densifies concrete, accelerates hydration, reduces permeability
Nano-TiO₂	Photocatalytic under UV, hydrophilic surfaces	Self-cleaning facades, glass, pavements that degrade NOx
Nano-clays	Layered silicates	Polymer nanocomposites, barrier properties
Nano-Al₂O₃, nano-Fe₂O₃, nano-CaCO₃	Fillers, reactivity	Cement composites
Silver nanoparticles	Antimicrobial	Coatings, water filters
Zinc oxide nanoparticles	UV absorption, antimicrobial	Coatings, sunscreens

Synthesis approaches

Approach	Principle	Methods
Top-down	Breaking bulk material into nanoscale	Ball milling, lithography, laser ablation, etching
Bottom-up	Building from atoms/molecules	Sol–gel process, chemical vapour deposition (CVD), precipitation, hydrothermal synthesis, self-assembly

Characterisation techniques

Technique	Information
Scanning electron microscopy (SEM)	Surface morphology, microstructure (e.g. C–S–H, cracks)
Transmission electron microscopy (TEM)	Internal structure, particle size at nanoscale
X-ray diffraction (XRD)	Crystal structure, phases, crystallite size
Atomic force microscopy (AFM)	Surface topography at atomic resolution
BET surface area analysis	Specific surface area by gas adsorption
Dynamic light scattering (DLS)	Particle size distribution in suspensions
FTIR, Raman spectroscopy	Chemical bonds, composition

Applications in construction

Nano-modified concrete — nano-silica for strength and durability; CNT/graphene for crack control and self-sensing (largely research/early applications).
Self-cleaning and air-purifying surfaces — TiO₂ coatings on facades, tiles, glass, pavement blocks.
Protective coatings — anti-corrosion, water-repellent (superhydrophobic), anti-graffiti, UV-resistant.
Smart windows and insulation — aerogels (nanoporous insulation), low-e coatings.
Nanosensors for structural health monitoring.
Water treatment — nano-filtration membranes, adsorbents.

Health, safety and environmental concerns

Fine particles may be inhaled or penetrate cells — potential toxicity (e.g. some CNTs likened to fibre hazards).
Handle with engineering controls, PPE, avoid dust; consider life-cycle release and disposal.
Regulations and standards are evolving.

Environmental chemistry

Structure of the atmosphere

Layer	Approximate altitude	Features
Troposphere	0 – about 10–15 km	Weather; temperature decreases with height; most air pollution
Stratosphere	up to about 50 km	Ozone layer (absorbs UV); temperature increases with height
Mesosphere	up to about 85 km	Coldest; meteors burn
Thermosphere (includes ionosphere)	above	Very high temperatures; auroras; radio wave reflection

Dry air composition by volume: N₂ ≈ 78%, O₂ ≈ 21%, Ar ≈ 0.93%, CO₂ ≈ 0.04% (and rising).

Air pollutants

Pollutant	Main sources	Effects
Particulate matter (PM₁₀, PM₂.₅)	Construction dust, vehicles, industries, burning	Respiratory and cardiovascular diseases; reduced visibility
Carbon monoxide (CO)	Incomplete combustion (vehicles)	Combines with haemoglobin (carboxyhaemoglobin) — reduces oxygen transport
Sulphur dioxide (SO₂)	Coal and oil burning, smelters	Respiratory irritation, acid rain, damage to buildings and vegetation
Nitrogen oxides (NOx)	High-temperature combustion (vehicles, power plants)	Respiratory effects, acid rain, photochemical smog precursor
Hydrocarbons / VOCs	Vehicles, solvents, paints	Smog formation; some carcinogenic (benzene)
Ground-level ozone (O₃)	Secondary — NOx + VOCs + sunlight	Respiratory damage, crop damage
Lead	Earlier leaded petrol, batteries, smelting	Neurotoxic, especially in children
CO₂, CH₄	Fossil fuels, cement, agriculture, landfills	Greenhouse gases

(See Air Pollution in Environmental Engineering for standards and control devices.)

Acid rain

Rain with pH below about 5.6 (normal rain is slightly acidic due to dissolved CO₂).
Formed from SO₂ and NOx: SO₂ → SO₃ → H₂SO₄; NO₂ → HNO₃.
Effects: acidification of lakes and soils, forest damage, corrosion of metals, deterioration of marble and limestone monuments (CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂ — "stone leprosy"; the Taj Mahal has been a well-known concern), damage to concrete and paints.
Control: flue gas desulphurisation, low-sulphur fuels, catalytic converters, liming of lakes.

Photochemical smog

Forms in sunny, warm, stagnant conditions from NOx + VOCs + sunlight → ozone, PAN (peroxyacetyl nitrate), aldehydes.
Brownish haze; eye irritation, respiratory problems, plant damage, rubber cracking.
Contrast: classical (London/reducing) smog — smoke + SO₂ + fog in cold humid conditions.

Ozone layer depletion

Stratospheric ozone absorbs harmful UV-B/UV-C radiation.
CFCs (refrigerants, aerosols, foam blowing agents) and halons release chlorine/bromine radicals under UV in the stratosphere: Cl• + O₃ → ClO• + O₂; ClO• + O → Cl• + O₂ — one chlorine atom can destroy many thousands of ozone molecules (catalytic cycle).
Ozone hole over Antarctica (polar stratospheric clouds).
Effects: skin cancer, cataracts, immune suppression, damage to crops and marine life.
Montreal Protocol (1987) — phase-out of ozone-depleting substances; ozone layer is recovering slowly.

Greenhouse effect and global warming

Greenhouse gases (CO₂, CH₄, N₂O, water vapour, fluorinated gases, O₃) are transparent to incoming short-wave solar radiation but absorb and re-emit outgoing long-wave infrared → warming.
The natural greenhouse effect keeps earth habitable; the enhanced greenhouse effect from human emissions causes global warming and climate change — rising temperatures, sea-level rise, extreme weather, glacier retreat.
Global warming potential (GWP) compares gases to CO₂ over a time horizon — methane and especially fluorinated gases have much higher GWP than CO₂.
International frameworks: UNFCCC, Kyoto Protocol (1997), Paris Agreement (2015).

Water pollution chemistry

Parameter / pollutant	Significance
Dissolved oxygen (DO)	Needed by aquatic life; saturation about 8–9 mg/L at 20–25 °C; low DO indicates organic pollution
Biochemical oxygen demand (BOD₅, 20 °C)	Oxygen consumed by microbes decomposing biodegradable organic matter in 5 days
Chemical oxygen demand (COD)	Oxygen equivalent of organic matter oxidised by strong chemical oxidant (dichromate) — includes non-biodegradable matter; COD > BOD
Heavy metals	Mercury (Minamata disease — methylmercury), cadmium (Itai-itai disease), lead (neurotoxicity), arsenic (arsenicosis — groundwater in parts of the Ganga–Brahmaputra plains), chromium (VI) (tanneries — carcinogenic)
Fluoride	Beneficial in small amounts; excess causes dental and skeletal fluorosis
Nitrates	Fertiliser runoff, sewage — methaemoglobinaemia ("blue baby syndrome"); eutrophication
Phosphates	Detergents, fertilisers — eutrophication (algal blooms, oxygen depletion)
Pesticides and persistent organic pollutants	Bioaccumulation and biomagnification (DDT)
Oil spills, microplastics, emerging contaminants	Ecological damage

(See Water Quality and Sewage Characteristics in Environmental Engineering.)

Soil pollution

Sources: industrial waste, excess fertilisers and pesticides, landfills and leachate, mining, e-waste, oil spills, construction and demolition waste.
Effects: reduced fertility, contamination of crops and groundwater, health risks.
Remediation: bioremediation, phytoremediation, soil washing, stabilisation/solidification, capping.

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