AQA GCSE Chemistry: Chemical Changes (Reactivity of Metals, Reactions of Acids, and Electrolysis)

Comprehensive vocabulary flashcards covering reactions of acids, titrations, salt preparation, the pH scale, electrolysis principles, aluminium extraction, electrode half equations, the reactivity series, and redox theory according to AQA GCSE Chemistry Topic 4.

Acid-Metal Reaction

A redox reaction where an acid reacts with a metal to produce a salt and hydrogen ($\text{acid} + \text{metal} \rightarrow \text{salt} + \text{hydrogen}$), in which the metal loses electrons (oxidation) and hydrogen ions gain electrons (reduction).

Bases

Substances, such as insoluble metal hydroxides and metal oxides, that neutralise acids to produce a salt and water ($\text{acid} + \text{base} \rightarrow \text{salt} + \text{water}$).

Alkalis

Soluble metal hydroxides that neutralise acids to produce a salt and water ($\text{acid} + \text{alkali} \rightarrow \text{salt} + \text{water}$) and produce $OH^-$ ions in aqueous solutions.

Acid-Metal Carbonate Reaction

A neutralisation reaction where an acid reacts with a metal carbonate to produce a salt, water, and carbon dioxide ($\text{acid} + \text{metal carbonate} \rightarrow \text{salt} + \text{water} + \text{carbon dioxide}$).

Crystallisation

A method used to prepare soluble salts by adding solid insoluble substance to acid until in excess, filtering out the excess solid to leave the salt solution, evaporating some water, and leaving the rest to evaporate slowly.

pH Scale

A scale from $0$ to $14$ that measures the acidity or alkalinity of a solution; a value of $7$ is neutral, below $7$ is acidic, and above $7$ is alkaline.

Neutralisation (Ionic Equation)

The reaction between hydrogen ions and hydroxide ions in aqueous solutions, represented by the ionic equation $H^+(aq) + OH^-(aq) \rightarrow H_2O(l)$.

Titration

A quantitative chemical procedure used to determine the exact reacting volumes of acid and alkali solutions using an indicator.

Titre

The volume of acid needed to exactly neutralise an alkali in a titration, determined by finding the difference between the initial and second burette readings.

Strong Acid

An acid that is completely ionised in aqueous solution, such as hydrochloric acid ($HCl$), nitric acid ($HNO_3$), and sulfuric acid ($H_2SO_4$).

Weak Acid

An acid that is only partially ionised in aqueous solution, such as ethanoic acid, citric acid, and carbonic acid.

Electrolysis

The chemical process of passing an electrical current through a molten ionic compound or aqueous solution to break it down into its constituent elements.

Electrolyte

A liquid or solution containing free-moving ions that conducts electricity and is decomposed during the process of electrolysis.

Cathode

The negatively charged electrode in an electrolytic cell towards which positively charged ions move and are reduced by gaining electrons.

Anode

The positively charged electrode in an electrolytic cell towards which negatively charged ions move and are oxidised by losing electrons.

Cryolite

A compound mixed with aluminium oxide during the industrial extraction of aluminium to lower its high melting point and reduce energy costs.

Anode Burning (Aluminium Extraction)

The process where carbon positive electrodes gradually burn away and require continual replacement because discharged oxygen reacts with the carbon to form carbon dioxide.

Cathode Rule (Aqueous Electrolysis)

The principle that hydrogen gas is produced at the cathode during electrolysis of an aqueous solution unless the metal present is less reactive than hydrogen.

Anode Rule (Aqueous Electrolysis)

The principle that a halogen element is discharged at the anode if halide ions ($Cl^-$, $Br^-$, $I^-$) are present; otherwise, oxygen is formed from the discharge of $OH^-$ ions.

Half Equation

An equation that models the oxidation or reduction reaction occurring at a single electrode during electrolysis, including the gain or loss of electrons represented by the symbol $e^-$.

Reactivity Series

The ranking of metals in order of their reactivity based on their reactions with water and dilute acids, reflecting their tendency to form positive ions.

Displacement Reaction

A chemical reaction where a more reactive metal takes the place of a less reactive metal from its compound.

Reduction with Carbon

A method used to extract metals less reactive than carbon from their metal oxides by the chemical removal (loss) of oxygen.

OIL RIG

A mnemonic used to remember electron movements in redox reactions: 'Oxidation Is Loss and Reduction Is Gain' of electrons.

Oxidation (in Terms of Electrons)

The loss of one or more electrons by an atom or ion during a chemical reaction (e.g., $Na \rightarrow Na^+ + e^-$).

Reduction (in Terms of Electrons)

The gain of one or more electrons by an atom or ion during a chemical reaction (e.g., $Na^+ + e^- \rightarrow Na$).