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Carbon and its compounds feels different from the rest of Class 10 chemistry. Instead of a few reactions to remember, you meet a whole family of names and structures. The good news is that the chapter runs on a small set of rules. Once you can count carbons, spot the functional group and apply four naming steps, most questions become routine. This post covers those rules with worked examples, the common slips, and a practice plan.
What does the syllabus include?
The CBSE Class X Science syllabus for 2026-27 lists: covalent bonds, the versatile nature of carbon, saturated and unsaturated hydrocarbons, homologous series, nomenclature of carbon compounds with halogen, alcohol, aldehyde and ketone groups, chemical properties (combustion, oxidation, addition and substitution), ethanol and ethanoic acid ("only properties and uses") and soaps and detergents. The examples here come from Chapter 4 of the NCERT Class 10 Science textbook. Check the syllabus for your own exam year.
Why does carbon form so many compounds?
NCERT gives two reasons. Carbon is tetravalent: it has four valence electrons and forms four covalent bonds. And it shows catenation: carbon atoms bond to each other in long chains, branched chains and rings. Covalent compounds have strong bonds within each molecule but weak forces between molecules, which is why most have low melting and boiling points and do not conduct electricity.
What is a homologous series?
A homologous series is a family of compounds with the same functional group, where each member differs from the next by a –CH₂– unit. Work it out for the alcohols:
CH₃OH (methanol): 12 + 4 + 16 = 32 u
C₂H₅OH (ethanol): 24 + 6 + 16 = 46 u
C₃H₇OH (propanol): 36 + 8 + 16 = 60 u
Each step adds CH₂, which is 12 + 2 = 14 u. NCERT notes that as molecular mass rises, physical properties such as melting and boiling points change gradually, while chemical properties stay similar because the functional group decides them.
The general formulae are worth knowing: alkanes CₙH₂ₙ₊₂ (propane, C₃H₈), alkenes CₙH₂ₙ (propene, C₃H₆) and alkynes CₙH₂ₙ₋₂ (propyne, C₃H₄).
How do you name a carbon compound?
NCERT's method has four steps. Here they are applied to CH₃CH₂CHO.
Count the carbons. Three, including the carbon in –CHO. So the parent chain is propane.
Identify the functional group. –CHO is an aldehyde, shown by the suffix "-al".
Drop the final "e" if the suffix starts with a vowel. Propane becomes propan, plus "al": propanal.
For double or triple bonds, replace "ane" with "ene" or "yne": propene, propyne.
Practise on these: CH₃COCH₃ is propanone (ketone, suffix "-one"); CH₃CH₂CH₂OH is propanol; CH₃CH₂COOH is propanoic acid; CH₃CH₂Br is bromoethane, because halogens take a prefix, not a suffix.
Which reactions should you know?
Combustion. Carbon compounds burn in oxygen to give carbon dioxide, water, heat and light.
Oxidation. Alkaline potassium permanganate or acidified potassium dichromate oxidises ethanol to ethanoic acid. NCERT calls these oxidising agents because they add oxygen.
Addition. Unsaturated hydrocarbons add hydrogen in the presence of a nickel or palladium catalyst. This is how vegetable oils are hydrogenated.
Substitution. In sunlight, chlorine replaces hydrogen atoms in an alkane one by one: CH₄ + Cl₂ → CH₃Cl + HCl.
For ethanoic acid, NCERT notes that vinegar is a 5 to 8 per cent solution of it in water, and that pure ethanoic acid melts at 290 K, so it can freeze in cold weather. It reacts with sodium carbonate and sodium hydrogencarbonate to give carbon dioxide, and with ethanol, using an acid catalyst, to give a sweet-smelling ester.
Which mistakes come up most often?
Writing a ketone with fewer than three carbons. A ketone's carbonyl carbon must be bonded to two other carbons, so propanone is the smallest one.
Wrong number of bonds on carbon. Every carbon in your structure needs exactly four bonds. Count them before you move on.
Calling isomers different compounds with different formulae. Structural isomers share a molecular formula. Butane, C₄H₁₀, has two: a straight chain and a branched one.
Confusing addition and substitution. Addition needs a double or triple bond; substitution happens to saturated compounds.
A practice routine for naming and reactions
Naming is a skill you build by producing answers, not by reading lists. In Roediger and Karpicke (2006), students who practised recalling a passage remembered more of it a week later than students who reread it. Apply that to this chapter.
Write 12 structures on cards: four alcohols, three aldehydes or ketones, three acids, two haloalkanes. Put the name on the back.
Each day, shuffle and name them aloud. Put the ones you miss in a separate pile and repeat those first next time.
Draw the electron dot structures of methane, ethene and ethyne from memory, then check against NCERT.
Write one equation for each reaction type above, labelling the reagent or condition.
If you get a name wrong and cannot see why, work through the reasoning step by step. The Fermi Problem Library has a step-by-step solver that explains the reasoning rather than printing an answer, which suits naming and equation questions. For the reaction types that come before this chapter, see our guide to chemical reactions in Class 10.
Start today by naming CH₃CH₂CH₂CHO without looking at the answer: count the carbons first.
