ICSE 2026 Chemistry Practice Paper 1 Vocabulary

Vocabulary practice flashcards based on the ICSE 2026 Chemistry Practice Paper 1.

Ionisation potential

The energy required to remove an electron from a neutral isolated gaseous atom and convert it into a positively charged gaseous ion.

Electronegativity

The tendency of an atom to attract electrons towards itself when combined in a covalent compound.

Empirical formula

The formula that represents the simplest ratio of the various elements present in one molecule of a compound.

Calcination

The process by which certain ores, especially carbonates, are converted to oxides by heating in the absence of air.

Non-polar covalent compound

A covalent compound in which bonding electrons are shared equally between the combining atoms, with no permanent dipole (such as $\text{CCl}_4$).

Acid (Arrhenius definition)

A chemical substance that releases hydronium ion ($\text{H}_3\text{O}^+$) as the only positive ion when dissolved in water.

Aqua fortis

The traditional chemical name for concentrated nitric acid ($\text{HNO}_3$).

Sal ammoniac

The common chemical name for ammonium chloride ($\text{NH}_4\text{Cl}$).

Efflorescent salt

A hydrated salt that loses its water of crystallization when exposed to air.

Esterification

The reaction between an alcohol (such as ethyl alcohol) and a carboxylic acid (such as acetic acid) in the presence of concentrated $\text{H}_2\text{SO}_4$ to produce an ester.

Lone pair of electrons

The unshared pair of electrons around an atom in the middle of a molecule of a polar covalent compound.

Ostwald's Process

An industrial manufacturing process for nitric acid involving the catalytic reaction of ammonia and air over a platinum ($\text{Pt}$) catalyst at $500^\circ\text{C}$.

Contact Process

An industrial manufacturing process for sulphuric acid in which sulphur dioxide and oxygen react over platinised asbestos or vanadium pentoxide ($\text{V}_2\text{O}_5$) at $450^\circ\text{C}$ to yield sulphur trioxide.

Strong electrolyte

A conducting substance, such as a molten ionic compound, that dissociates completely into mobile ions and easily conducts electric current.

Weak electrolyte

An electrolytic solution that contains solvent molecules, solute molecules, and ions formed by the partial dissociation of solute molecules.

Non-electrolyte

A chemical compound (such as carbon tetrachloride) that consists entirely of molecules and does not conduct electricity due to the absence of ions.

Vapour density

The relative gas density quantity that relates to molecular weight according to the equation $\text{Molecular mass} = 2 \times \text{Vapour density}$.

Alkali metals

Group 1 elements that possess a single valence electron, making them easily oxidised and powerful reducing agents.

Upward displacement of air

The laboratory collection method used for dry hydrogen chloride gas due to its higher density compared to air.

Quick lime ($\text{CaO}$)

Calcium oxide; a basic drying agent that cannot be used for drying hydrogen chloride gas because it undergoes an acid-base neutralization reaction with it.

Hydrogen sulphide ($\text{H}_2\text{S}$)

A toxic gas that turns moist lead acetate paper silvery black through the formation of lead sulphide.

Nitric oxide ($\text{NO}$)

A colorless gaseous oxide that turns reddish brown when oxidized by atmospheric oxygen to nitrogen dioxide ($\text{NO}_2$).

Sulphur dioxide ($\text{SO}_2$)

A reducing gas that turns acidified potassium dichromate solution green.

2-Methylpropane

A branched alkane with molecular formula $\text{C}_4\text{H}_{10}$ consisting of a propane chain with a methyl branch on carbon-2.

Ethanoic acid

The IUPAC name for acetic acid, an organic carboxylic acid with the formula $\text{CH}_3\text{COOH}$.

Butan-2-ol

A four-carbon secondary alcohol containing a hydroxyl functional group ($-\text{OH}$) attached to carbon-2.

Molar volume at STP

The constant volume occupied by one mole of any ideal gas at standard temperature and pressure, equal to $22.4\,\text{dm}^3$.

Gay-Lussac's Law of Combining Volumes

The law stating that gaseous reactants and products combine and form in simple whole-number volume ratios when measured under identical temperature and pressure.

Cathode

The negatively charged electrode in an electrolytic cell at which metal ions and hydrogen ions are discharged by reduction.

Electro-refining

An industrial electrolytic process used to purify impure metals by depositing pure metal onto a cathode from an electrolyte solution.