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Class 10 Science examination papers. Since the archive does
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questions are not labelled as a specific year's PYQ here.
Official CBSE Previous Year Papers
Class 10 Science – 2026
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Chapter-Focused Practice
Practice Question 1
Why is carbon able to form such a large number of compounds?
Carbon has valency four and can form strong bonds with other
carbon atoms. This tetravalency and catenation allow it to
form straight chains, branches and rings.
Practice Question 2
Differentiate between saturated and unsaturated hydrocarbons.
Saturated hydrocarbons contain only carbon-carbon single
bonds.
Unsaturated hydrocarbons contain one or more carbon-carbon
double or triple bonds.
Practice Question 3
What is a homologous series?
A homologous series is a family of organic compounds having
the same functional group and similar chemical properties,
where consecutive members differ by a CH₂ unit.
Practice Question 4
Identify the functional group present in ethanol and
ethanoic acid.
Ethanol → –OH (hydroxyl/alcohol group)
Ethanoic acid → –COOH (carboxylic acid group)
Practice Question 5
Write the combustion equation for methane.
CH₄ + 2O₂ → CO₂ + 2H₂O + Energy
Practice Question 6
What is an addition reaction? Give one example.
An addition reaction involves addition of atoms or groups
across a carbon-carbon multiple bond.
Practice Question 7
What is esterification?
Esterification is the reaction of an alcohol with a
carboxylic acid in the presence of an acid catalyst to
form an ester and water.
Practice Question 8
Write the reaction between ethanol and ethanoic acid.
CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O
Practice Question 9
Why does soap not work efficiently in hard water?
Calcium and magnesium ions in hard water react with soap
and form insoluble scum, which reduces its cleansing action.
Practice Question 10
Explain the cleansing action of soap.
Soap molecules have a hydrophobic hydrocarbon part and a
hydrophilic ionic part. The hydrophobic part interacts with
oily dirt while the hydrophilic part remains associated
with water, allowing the dirt to be removed during washing.
Quick Revision Before PYQs
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Tetravalency and catenation of carbon.
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Covalent bonds and properties of covalent compounds.
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Saturated and unsaturated hydrocarbons.
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Alkanes, alkenes and alkynes.
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Homologous series and nomenclature.
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Important functional groups.
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Combustion, oxidation, addition and substitution reactions.
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Ethanol and ethanoic acid.
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Esterification.
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Soaps, detergents and micelles.