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Chemical Changes and Reactions — Syllabus

ICSE · Class 9 · Chemistry

What Chemical Changes and Reactions covers in ICSE Class 9 Chemistry: 4 topics, for the 2026-27 session. Part of the ICSE Class 9 Chemistry syllabus.

43 questions36 flashcards9 formulas & key relations5 concepts

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An infographic illustrating various conditions required for chemical reactions to occur, such as close contact, solution, heat, light, electricity, pressure, and catalysts, with a simple example for e
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4 Topics · ICSE Class 9 Chemistry · 2026-27

Topics in Chemical Changes and Reactions

1

1. Chemical Reaction and Its Signs

  • A chemical reaction is the process of breaking the chemical bonds of the reactants and making new bonds to form new products.
  • A chemical bond is the force that holds the atoms of a molecule together, as in a compound.
  • Chemical reactions occur when particles collide, usually by close contact or by supply of energy.
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2. Types of Chemical Reactions

  • The main types of chemical reactions are direct combination, decomposition, displacement, and double decomposition.
  • In a combination reaction, two or more substances combine to form a single product.
  • In a decomposition reaction, a compound breaks into simpler substances or elements.
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3. Decomposition, Reversible Reactions, and Thermal Dissociation

  • Decomposition can happen by heat, light, or electricity.
  • Thermal decomposition is decomposition brought about by heat.
  • Thermal dissociation is a simultaneous reversible decomposition reaction brought about only by heat.
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4. Catalysts, Promoters, and Activity Series

  • Catalysts speed up or slow down the rate of reactions, but catalysts themselves do not take part in the reaction.
  • When a catalyst accelerates a reaction, it is a positive catalyst.
  • A catalyst employed to retard a reaction is a negative catalyst.

Key Concepts

Central concept: Chemical change is the breaking of old bonds and formation of new bonds that creates new substances, often with energy change and observable signs such as gas, colour change, precipitate, or change of state.

Chemical reactionConditions for reactionObservable changesDirect combinationDecompositionDisplacementDouble decompositionEnergy changes

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Frequently Asked Questions

What are the important topics in Chemical Changes and Reactions for ICSE Class 9 Chemistry?
Key topics in Chemical Changes and Reactions include Chemical Reaction and Its Signs, Types of Chemical Reactions, Decomposition, Reversible Reactions, and Thermal Dissociation, Catalysts, Promoters, and Activity Series. Study these first, then practise questions on each for Class 9 exams.
How should I revise Chemical Changes and Reactions for Class 9 exams?
Learn the core ideas first, then work through the 43 practice questions on Chemical Changes and Reactions. Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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