Chapter 1 – Chemical Reactions and Equations (NCERT)

Vocabulary flashcards summarizing essential terms and definitions from NCERT Chapter 1: Chemical Reactions and Equations.

Chemical reaction

A process in which one or more reactants are transformed into new substances called products.

Indicators of a chemical reaction

Observable signs such as colour change, temperature change, evolution of gas, formation of a precipitate, or change in state.

Chemical equation

A symbolic representation of a chemical reaction using element symbols and chemical formulas for reactants and products.

Balanced chemical equation

An equation in which the number of atoms for each element is equal on both sides, satisfying the Law of Conservation of Mass.

Law of Conservation of Mass

Scientific law stating that mass is neither created nor destroyed in a chemical reaction.

Combination reaction

A reaction where two or more substances combine to form a single product. Example: CaO + H₂O → Ca(OH)₂.

Decomposition reaction

A reaction in which a single compound breaks into two or more simpler substances.

Thermal decomposition

Decomposition brought about by heat, e.g., CaCO₃ →(heat) CaO + CO₂.

Photodecomposition

Decomposition caused by light, e.g., 2AgCl →(sunlight) 2Ag + Cl₂.

Electrolytic decomposition

Decomposition driven by electric current, e.g., 2H₂O →(electricity) 2H₂ + O₂.

Displacement reaction

A reaction in which a more reactive element displaces a less reactive element from its compound, e.g., Zn + CuSO₄ → ZnSO₄ + Cu.

Double displacement reaction

A reaction where the ions of two compounds exchange partners, often forming a precipitate, e.g., Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl.

Precipitate

An insoluble solid formed during a chemical reaction in solution.

Oxidation (in redox)

Process involving gain of oxygen or loss of hydrogen by a substance.

Reduction (in redox)

Process involving gain of hydrogen or loss of oxygen by a substance.

Redox reaction

A reaction involving simultaneous oxidation and reduction, e.g., CuO + H₂ → Cu + H₂O.

Corrosion

Gradual destruction of metals by chemical reaction with air and moisture; example: rusting of iron.

Rust

Hydrated iron(III) oxide (Fe₂O₃·xH₂O) formed during corrosion of iron.

Galvanization

Protective coating of iron or steel with zinc to prevent corrosion.

Rancidity

Oxidative spoilage of fats and oils leading to bad smell and taste.

Antioxidants (BHA, BHT)

Additives that prevent rancidity by slowing oxidation of fats and oils.

Magnesium combustion

Reaction where Mg burns in O₂ with a bright white flame forming white MgO ash.

Ferrous sulphate decomposition

Heating 2FeSO₄ causes a colour change from green to brown, producing Fe₂O₃, SO₂ and SO₃ gases.

Exothermic reaction

Reaction that releases heat to the surroundings, such as CaO + H₂O → Ca(OH)₂ + heat.