Chemical Reactions and Equations

Vocabulary review covering terms, definitions, symbols, and concepts from the chapter on Chemical Reactions and Equations.

Chemical Reaction

A process involving a chemical change in which initial substances change in nature and identity to form new substances by breaking and making bonds between atoms.

Reactants

The initial substances that undergo a chemical change during a chemical reaction, written on the left-hand side (LHS) of a chemical equation with a plus sign ($+$") between them.

Products

The new substances formed during a chemical reaction, written on the right-hand side (RHS) of a chemical equation with a plus sign ($+$") between them.

Word-Equation

A chemical equation written using the names of reactants and products, with an arrow between them pointing toward the products to indicate the direction of the reaction.

Skeletal Chemical Equation

An unbalanced chemical equation written using chemical formulae where the number of atoms of each element is not equal on both sides of the arrow.

Balanced Chemical Equation

A chemical equation in which the total number of atoms of each element is identical on both the reactant and product sides, satisfying the law of conservation of mass.

Law of Conservation of Mass

A fundamental law stating that mass can neither be created nor destroyed in a chemical reaction, requiring the total mass of the products to equal the total mass of the reactants.

Hit-and-Trial Method

A method of balancing chemical equations by making trials to equalise atoms on both sides using the smallest whole-number coefficients.

Aqueous ($(aq)$)

A state symbol used in a chemical equation to indicate that a reactant or product is present as a solution in water.

Combination Reaction

A reaction in which two or more substances (elements or compounds) combine to form a single product.

Quick Lime

The common name for calcium oxide ($CaO$), which reacts vigorously with water to form slaked lime and releases a large amount of heat.

Slaked Lime

The common name for calcium hydroxide ($Ca(OH)_2$), produced by reacting calcium oxide with water and commonly used for whitewashing walls.

Exothermic Chemical Reaction

A chemical reaction in which heat energy is released along with the formation of products (e.g., respiration, burning of natural gas, and decomposition of vegetable matter).

Respiration

An exothermic process in which glucose combines with oxygen inside body cells to release energy: $C_6H_{12}O_6(aq) + 6O_2(aq) \rightarrow 6CO_2(aq) + 6H_2O(l) + \text{energy}$.

Decomposition Reaction

A reaction in which a single reactant breaks down into two or more simpler products.

Thermal Decomposition

A decomposition reaction that is driven by the application of heat (e.g., heating limestone, $CaCO_3$, to yield quick lime, $CaO$, and carbon dioxide, $CO_2$).

Endothermic Reaction

A chemical reaction in which energy is absorbed from the surroundings in the form of heat, light, or electricity to break down the reactants.

Displacement Reaction

A chemical reaction in which a more reactive element displaces or removes another element from its compound in solution.

Precipitate

An insoluble solid substance that separates out of a liquid solution during a chemical reaction.

Precipitation Reaction

Any chemical reaction between solutions that produces an insoluble precipitate.

Double Displacement Reaction

A chemical reaction in which two compounds react by exchanging their ions to form two new compounds.

Oxidation

A chemical process that involves the gain of oxygen or the loss of hydrogen by a substance during a reaction.

Reduction

A chemical process that involves the loss of oxygen or the gain of hydrogen by a substance during a reaction.

Redox Reaction

A chemical reaction in which one reactant undergoes oxidation while another reactant undergoes reduction simultaneously.

Corrosion

The slow degradation of a metal when attacked by substances in the surrounding environment, such as moisture and acids (e.g., rusting of iron, black coating on silver, green coating on copper).

Rusting of Iron

A specific corrosion process where iron surfaces become coated with a reddish-brown powder after prolonged exposure to a humid atmosphere.

Rancidity

The spoiling of fats and oils resulting from oxidation, causing an unpleasant change in their taste and smell over time.

Antioxidants

Substances added to foods containing fats and oils to prevent or slow down oxidation and rancidity.