Chemical Reactions and Equations – Vocabulary Flashcards

Vocabulary flashcards covering key terms and definitions from the lecture on Chemical Reactions and Equations.

Chemical Reaction

A process in which the nature and identity of substances change, forming new substances with different properties.

Reactant

A substance that undergoes change during a chemical reaction; written on the left-hand side of a chemical equation.

Product

A new substance formed in a chemical reaction; written on the right-hand side of a chemical equation.

Word Equation

A shorthand sentence describing a reaction using the names of reactants and products, e.g., Magnesium + Oxygen → Magnesium oxide.

Skeletal Chemical Equation

An unbalanced equation written with chemical formulae that does not yet obey the law of conservation of mass.

Balanced Chemical Equation

A chemical equation in which the number of atoms of each element is equal on both sides, satisfying the law of conservation of mass.

Law of Conservation of Mass

Principle stating that mass can neither be created nor destroyed in a chemical reaction; total mass of reactants equals total mass of products.

Hit-and-Trial Method

Common procedure for balancing equations by adjusting coefficients until atom counts match on both sides.

Physical-State Symbols

Notations (s), (l), (g), and (aq) that indicate solid, liquid, gas, and aqueous states in a chemical equation.

Combination Reaction

Reaction in which two or more substances combine to form a single product, e.g., CaO + H₂O → Ca(OH)₂.

Exothermic Reaction

Chemical reaction that releases heat energy to the surroundings, often making the reaction mixture warm.

Endothermic Reaction

Chemical reaction that absorbs energy (heat, light, or electricity) from the surroundings.

Decomposition Reaction

Reaction in which a single compound breaks down into two or more simpler substances, often requiring energy input.

Thermal Decomposition

Decomposition reaction driven by heat, e.g., CaCO₃ → CaO + CO₂ on heating.

Electrolysis

Decomposition of a substance by passing an electric current through it, such as the electrolysis of water.

Photolytic Decomposition

Decomposition reaction initiated by light energy, e.g., 2AgCl → 2Ag + Cl₂ in sunlight.

Displacement Reaction

Reaction in which a more reactive element displaces a less reactive element from its compound, e.g., Fe + CuSO₄ → FeSO₄ + Cu.

Double Displacement Reaction

Reaction involving exchange of ions between two compounds, producing two new compounds, often with a precipitate.

Precipitation Reaction

Reaction in which an insoluble substance (precipitate) is settled in the solution after mixing two soluble reactants, resulting in the formation of a solid.

Oxidation

Process in which a substance gains oxygen or loses hydrogen during a reaction.

Reduction

Process in which a substance loses oxygen or gains hydrogen during a reaction.

Redox Reaction

Reaction involving simultaneous oxidation of one substance and reduction of another.

Quick Lime (Calcium Oxide)

CaO; a white solid produced by heating limestone, used in cement manufacture and combination reactions with water.

Slaked Lime (Calcium Hydroxide)

Ca(OH)₂; product of quick lime reacting with water, used in whitewashing walls.

Corrosion

Gradual deterioration of a metal by reaction with environment (e.g., rusting of iron) forming oxide or other compounds.

Rancidity

Spoilage of fats and oils due to oxidation, leading to unpleasant odour and taste.

Respiration

Exothermic biological reaction in which glucose combines with oxygen to produce CO₂, H₂O, and energy.

Photosynthesis

Process by which green plants convert CO₂ and H₂O into glucose and O₂ using sunlight and chlorophyll.

Law of Conservation of Mass – Application

Reason why chemical equations must be balanced: the total atoms (and hence mass) on both sides must be equal.

Precipitate

An insoluble solid that separates from a solution during a chemical reaction, such as BaSO₄ in Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl.