Reactions of acids key terms

Limewater

A dilute solution of calcium hydroxide used to test for carbon dioxide. In Neutralisation of acids and salt production, this term helps explain describe the test for carbon dioxide using limewater for AQA GCSE Chemistry 8462 Unit 4.4.

Carbon dioxide test

The process of bubbling carbon dioxide through limewater, which turns milky if carbon dioxide is present.

Soluble salt

A salt that can dissolve in water to give a clear solution. In Soluble salts, this term helps explain describe how to prepare a soluble salt from an acid and an insoluble reactant for AQA GCSE Chemistry 8462 Unit 4.4.

Acid–insoluble reactant

A solid that does not dissolve in water but reacts with an acid to form a soluble salt.

Insoluble solid

A substance that does not dissolve in a solvent, used in excess to ensure complete reaction with an acid.

Excess reactant

A reactant that is present in a greater amount than necessary to completely react with another reactant.

filtration

A separation technique that removes solid particles from a liquid by passing the mixture through a porous medium, allowing the liquid to pass while retaining the solid.

excess insoluble solid

A solid reactant added in a quantity greater than stoichiometrically required, ensuring that the reaction proceeds to completion and the remaining solid can be separated by filtration.

evaporation

The process of turning a liquid into a gas, leaving dissolved solids behind. In Soluble salts, this term helps explain describe how evaporation and crystallisation produce a pure dry salt sample for AQA GCSE Chemistry 8462 Unit 4.4.

crystallisation

The formation of solid crystals from a solution when the solute becomes supersaturated and precipitates out.

soluble salt

A salt that dissolves in water to form a solution. In Soluble salts, this term helps explain identify suitable apparatus for preparing, filtering and crystallising a soluble salt. (AT 2, AT 3, AT 4, AT 6) for AQA GCSE Chemistry 8462 Unit 4.4.

crystallisation

The process of forming solid crystals from a solution. In Soluble salts, this term helps explain identify suitable apparatus for preparing, filtering and crystallising a soluble salt. (AT 2, AT 3, AT 4, AT 6) for AQA GCSE Chemistry 8462 Unit 4.4.

soluble salt

A salt that dissolves in water to form a solution. In Soluble salts, this term helps explain write word equations for soluble salt preparation reactions for AQA GCSE Chemistry 8462 Unit 4.4.

word equation

A representation of a chemical reaction using the names of the reactants and products.

soluble salt

A salt that dissolves in water to form a solution. In Soluble salts, this term helps explain write balanced symbol equations for soluble salt preparation when formulae are supplied for AQA GCSE Chemistry 8462 Unit 4.4.

balanced symbol equation

An equation that shows the reactants and products of a chemical reaction with equal numbers of atoms for each element on both sides.

soluble salt

A salt that dissolves in water to form a solution. In Soluble salts, this term helps explain explain how to obtain a pure dry sample of a named soluble salt in the required practical for AQA GCSE Chemistry 8462 Unit 4.4.

required practical

A hands-on experiment conducted to demonstrate a scientific principle or process.

Acid handling

Safe practices for handling acids, including wearing protective equipment, using fume hoods, and avoiding splashes.

Controlled heating

Gradual, monitored heating of acid solutions to prevent rapid boiling, splattering, and pressure build‑up.

pH scale

A scale used to measure the acidity or alkalinity of a solution, ranging from 0 (acidic) to 14 (alkaline), with 7 being neutral.

neutral solution

A solution that has a pH of 7, indicating it is neither acidic nor alkaline. In The pH scale and neutralisation, this term helps explain use the pH scale to classify solutions as acidic, neutral or alkaline for AQA GCSE Chemistry 8462 Unit 4.4.

universal indicator

A pH indicator that changes color to indicate the acidity or alkalinity of a solution.

pH meter

An electronic device used to measure the pH level of a solution accurately. In The pH scale and neutralisation, this term helps explain describe universal indicator and pH meters as methods for measuring pH for AQA GCSE Chemistry 8462 Unit 4.4.

Hydrogen ion (H+)

A positively charged ion formed when an acid dissociates in aqueous solution. In The pH scale and neutralisation, this term helps explain explain that acids produce hydrogen ions, H+, in aqueous solution for AQA GCSE Chemistry 8462 Unit 4.4.

Aqueous solution

A solution in which water is the solvent, commonly used to describe the state of acids and bases.

alkali

A substance that produces hydroxide ions, OH-, in aqueous solution. In The pH scale and neutralisation, this term helps explain explain that alkalis produce hydroxide ions, OH-, in aqueous solution for AQA GCSE Chemistry 8462 Unit 4.4.

hydroxide ion

A negatively charged ion (OH-) formed when an alkali dissolves in water. In The pH scale and neutralisation, this term helps explain explain that alkalis produce hydroxide ions, OH-, in aqueous solution for AQA GCSE Chemistry 8462 Unit 4.4.

neutralisation

The reaction between an acid and a base or alkali to produce salt and water. In The pH scale and neutralisation, this term helps explain describe neutralisation in terms of hydrogen ions reacting with hydroxide ions to produce water for AQA GCSE Chemistry 8462 Unit 4.4.

hydrogen ion

A positively charged ion (H+) that is produced by acids in aqueous solution. In The pH scale and neutralisation, this term helps explain describe neutralisation in terms of hydrogen ions reacting with hydroxide ions to produce water for AQA GCSE Chemistry 8462 Unit 4.4.