Carbon and its Compounds · Class 10 Science: quick revision, 60 bites

Why Carbon Shares

Four in hand, nowhere to throw

Carbon (2,4) can neither lose nor gain four electrons — both routes cost impossible energy. Its only road to the octet is **sharing electron pairs** with other atoms: the **covalent bond**. Every carbon compound is covalent.

Takeaway. Can't give, can't take — so carbon shares.

The Covalent Bond

The bond, defined

Takeaway. One shared pair = one covalent bond.

Single, Double, Triple

One, two, three pairs

Takeaway. Count the needs, pair them up — the bond order follows.

Methane's Electron Story

The simplest carbon compound

In CH₄, carbon shares one electron pair with EACH of four hydrogens. Result: carbon's octet complete, each hydrogen's duet complete, four strong single bonds. Methane — cooking gas's main component and the head of the alkane family.

Takeaway. CH₄ = carbon's four sockets, each filled by a hydrogen.

Properties of Covalent Compounds

The anti-ionic profile

Takeaway. Molecules, not ions — hence soft-melting insulators.

Strong Bonds, Weak Neighbours

The strong-weak paradox

Takeaway. Within: strong. Between: weak. Melting fights 'between'.

Catenation

Superpower #1

C-C bonds are strong because carbon's small size holds the shared pairs tightly — chains of thousands of atoms (polymers) survive intact.

Takeaway. Carbon links to itself endlessly — the chain-maker.

Tetravalency

Superpower #2

Four sockets per atom on unlimited chains — the combinatorial explosion behind millions of compounds.

Takeaway. Four bonds each, every atom — possibilities multiply.

Millions of Compounds

The census

Catenation × tetravalency ≈ over **10 million known carbon compounds** — more than all other elements' compounds COMBINED. Fuels, plastics, medicines, fabrics, food and the molecules of life are all entries in carbon's catalogue.

Takeaway. One element out-writes the rest of the periodic table.

Diamond vs Graphite

Same atoms, opposite lives

Takeaway. Architecture — not atoms — writes the properties.

Fullerenes

The carbon football

The third allotrope family: closed cages of carbon. **C-60**, the first found, arranges 60 atoms exactly like a football's pattern of hexagons and pentagons — named after architect Buckminster Fuller's dome designs.

Takeaway. C-60: sixty carbons folded into a football.

Polythene — Chains by the Thousand

Catenation you can buy

Takeaway. Every plastic bag is catenation made visible.

Worked: Water and Nitrogen

Dot-structure drill

Takeaway. Count needs, share pairs, verify octets.

Board Favourites

The reliable four

Takeaway. Four answers carry this topic's marks.

Memory Pack

Whole topic in three lines

Takeaway. Three lines, the whole bonding story.

Hydrocarbons

The simplest carbon family

Takeaway. C + H only — three families by bond type.

Alkane, Alkene, Alkyne

Three formulas rule them all

Takeaway. Three families, three formulas — count and classify.

Saturated vs Unsaturated

Full or hungry?

Takeaway. Single-bonded = full; multiple-bonded = hungry and reactive.

Alkenes and Alkynes Start at C₂

Why no 'methene' exists

A double or triple bond must connect TWO carbon atoms — a single carbon has no partner. So the alkene and alkyne series both begin at ethene/ethyne (n = 2), while alkanes start at methane (n = 1).

Takeaway. Multiple bonds need two carbons — no C₁ member.

Structural Isomers

Same formula, different skeletons

Isomerism starts at C₄ for alkanes and multiplies explosively with size.

Takeaway. One formula can hide several different compounds.

The Homologous Series

Chemistry's family system

Takeaway. One formula, one chemistry, a CH₂ staircase.

The CH₂ Ladder

The staircase in numbers

CH₄ → C₂H₆ → C₃H₈ → C₄H₁₀ — each step adds exactly **CH₂ (mass 14 u)**. Boiling points climb with each step: methane and ethane are gases, mid-members liquids, long chains waxes — the same chemistry in progressively heavier bodies.

Takeaway. +CH₂ per step; physics shifts, chemistry stays.

Functional Groups

The personality tag

Takeaway. The group, not the chain, decides the chemistry.

The IUPAC Roots

Five roots to name the world

Carbon count → root: **meth**(1), **eth**(2), **prop**(3), **but**(4), **pent**(5), hex(6). Add the bond suffix (-ane/-ene/-yne), then the group suffix if any. Ethanol = eth + an + ol; propyne = prop + yne.

Takeaway. Root + bond + group = the whole name.

Worked: Four Names

Name-decoding drill

Takeaway. Read root for size, suffix for family — the name IS the structure.

n-Butane vs Isobutane

The butane twins

Takeaway. The first isomer pair every exam asks: straight vs branched C₄H₁₀.

The Alkanes in Your Kitchen and Car

Fuels you already know by name

Takeaway. Hydrocarbon names hide inside every fuel label.

-ol vs -al vs -one

The suffix minefield

Takeaway. ol-alcohol, al-aldehyde, one-ketone — never mix.

Board Favourites

The reliable five

Takeaway. Formulas, homologues, isomers, groups, names — the five staples.

Memory Pack

Whole topic in three lines

Takeaway. Three lines, the whole naming toolkit.

Combustion

Why carbon compounds are fuels

Carbon and its compounds release large heat on burning — the entire fuel economy (CNG, LPG, petrol, coal, wax) runs on this one reaction.

Takeaway. Burn a carbon compound → CO₂ + water + the energy we live on.

Blue vs Sooty

Read the flame like a chemist

Takeaway. The flame's colour reports the fuel's bonds and the air supply.

When the Stove Flame Yellows

The blackened kadhai clue

Takeaway. Yellow flame at home = oxygen problem, not fuel problem.

Combustion Pollution

The burn's dark side

Coal and petroleum contain traces of sulphur and nitrogen; burning them releases **SO₂ and oxides of nitrogen** — the gases that dissolve in rain as ACID RAIN. Cleaner fuels (CNG) and scrubbers exist precisely to cut these.

Takeaway. Fossil-fuel burning writes the acid-rain story.

Oxidation with KMnO₄

Alcohol to vinegar-acid, on command

Alkaline potassium permanganate (or acidified potassium dichromate) supplies oxygen — an **oxidising agent**, consumed in the act.

Takeaway. Oxidising agents turn alcohols into carboxylic acids.

The Colour Test of Oxidation

The vanishing purple

Takeaway. Purple fades while alcohol lasts; stays when it's gone.

KMnO₄ Is Consumed

Agent, not catalyst

Takeaway. Oxidant is spent; catalyst survives.

Addition Reactions

Opening the double bond

Double and triple bonds OPEN and add atoms across themselves — the signature reaction (and test) of unsaturation. Nickel or palladium catalyses the hydrogen addition.

Takeaway. Unsaturated compounds add H₂ over Ni — becoming saturated.

Hydrogenation of Vegetable Oils

Oil to ghee in a factory

Takeaway. Vanaspati = vegetable oil + H₂ + Ni — addition industrialised.

Saturated vs Unsaturated — the Health Note

The label on your oil packet

Excess **saturated fats** (solid, hydrogenated) are linked to heart problems; **unsaturated oils** are generally the healthier cooking medium. The chemistry terms of this chapter are printed on every cooking-oil label.

Takeaway. For health: prefer the unsaturated oils.

Substitution Reactions

The saturated workaround

Alkanes have no bonds to open — so chlorine SWAPS with their hydrogens one by one (on to CH₂Cl₂, CHCl₃, CCl₄). Sunlight starts the reaction.

Takeaway. Saturated compounds substitute; sunlight is the switch.

Addition vs Substitution

The pairing that sorts every MCQ

Takeaway. Bond type decides the reaction type.

Diamond and Graphite Burn Alike

Same ash for gem and pencil

Burn a diamond or graphite in oxygen and both leave nothing but CO₂ — historically the cleanest proof that both are pure carbon. (An expensive experiment with the diamond.)

Takeaway. Combustion is carbon's identity test.

Board Favourites

The reliable five

Takeaway. Five staples carry this topic's marks.

Memory Pack

Whole topic in three lines

Takeaway. Three lines, four reactions.

Ethanol — Properties and Uses

The spirit in the sanitiser

Takeaway. Ethanol: the neutral, water-loving workhorse solvent.

Ethanol + Sodium

The neutral compound that pops

The evolved gas burns with a POP — the same hydrogen test as with acids, from a litmus-neutral liquid.

Takeaway. Na + alcohol → ethoxide + popping hydrogen.

Dehydration to Ethene

Stealing the water out

Concentrated H₂SO₄ acts as a **dehydrating agent** — it removes a water molecule from ethanol, leaving the unsaturated ethene.

Takeaway. Hot conc. H₂SO₄ pulls water out — alcohol becomes alkene.

Ethanoic Acid — the Weak Acid

Vinegar's molecule

Takeaway. Weak but complete acid — and 'glacial' when pure and cold.

Ethanoic Acid + Carbonates

The fizz that identifies acids

With NaOH it neutralises quietly: CH₃COOH + NaOH → CH₃COONa + H₂O.

Takeaway. Carbonate fizz + base neutralisation — the acid repertoire.

Esterification

The perfume reaction

Takeaway. Acid + Alcohol + Acid-catalyst = Aroma.

Saponification

The reaction that makes soap

Treat an ester with sodium hydroxide and it splits back: **ester + NaOH → alcohol + sodium salt of the acid**. When the ester is a FAT (long-chain fatty acid ester), that sodium salt is **SOAP** — the reaction is called **saponification**.

Takeaway. Alkali splits esters; fats + NaOH = soap.

The Soap Molecule

One molecule, two loyalties

Takeaway. Soap = fatty-acid salt with a two-sided molecule.

Micelles — How Soap Cleans

The cleaning machine

Takeaway. Tails trap the grease; heads ferry it away in water.

Soap vs Hard Water

When lather refuses to form

Hard water carries **Ca²⁺ and Mg²⁺** ions. They react with soap to form an **insoluble curdy precipitate — SCUM** — wasting the soap and blocking lather. The classic test for hard water is exactly this failed lather.

Takeaway. Ca²⁺/Mg²⁺ + soap = scum, not suds.

Soap vs Detergent

The washing-powder upgrade

Takeaway. Same tail-head design; the head decides the hard-water fate.

Methanol and Denatured Alcohol

The poisoned bottle

Takeaway. Methanol kills; the dye on industrial alcohol is a warning label.

Testing for Hard Water

The two-tube lather test

Takeaway. Lather comparison = the classroom hardness test.

Board Favourites

The bankers of this topic

Takeaway. Five staples carry the topic's marks.

Memory Pack

Whole topic in three lines

Takeaway. Three lines, the two stars and the soap.