GCSE Chemistry – End-of-Year 9 Core Vocabulary

60 vocabulary flashcards covering key GCSE Chemistry terms and concepts from the lecture notes.

Melting

Change of state from solid to liquid.

Sublimation

Change of state directly from solid to gas.

Boiling / Evaporation

Change of state from liquid to gas.

Condensation

Change of state from gas to liquid.

Freezing

Change of state from liquid to solid.

Solid

Particles packed closely together and vibrating in fixed positions.

Liquid

Particles packed closely together but able to move past one another.

Gas

Particles far apart and moving rapidly in all directions.

Density trend (states)

Gas < Liquid < Solid (increasing density).

Particle energy trend (states)

Solid < Liquid < Gas (increasing energy).

Solute

Solid that dissolves in a solvent.

Solvent

Liquid in which a solute dissolves.

Saturated solution

Solution in which no more solute will dissolve at a given temperature.

Solubility (unit)

g of solute per 100 g of solvent (g/100 g).

Solubility–temperature trend (solids)

Solubility of most solids increases as temperature rises.

Solubility–temperature trend (gases)

Solubility of gases decreases as temperature rises.

Diffusion

Spreading of particles from a region of high concentration to low concentration.

Element

Substance made of only one type of atom.

Compound

Substance formed when two or more different atoms are chemically bonded.

Atom

Smallest particle of an element that retains the element’s properties.

Molecule

Two or more atoms chemically combined.

Isotope

Atoms of the same element with the same number of protons but different numbers of neutrons.

Relative atomic mass (Aᵣ)

Weighted average of the mass numbers of an element’s isotopes.

Proton

Sub-atomic particle; mass = 1, charge = +1; located in nucleus.

Neutron

Sub-atomic particle; mass = 1, charge = 0; located in nucleus.

Electron

Sub-atomic particle; mass ≈ 1/1840, charge = –1; orbits the nucleus.

Atomic number

Number of protons in an atom’s nucleus.

Mass number

Total number of protons plus neutrons in an atom.

Electron shell (energy level)

Region around nucleus where electrons are found; first holds 2, second 8, third 8.

Group (Periodic Table)

Vertical column; elements have same number of outer-shell electrons.

Period (Periodic Table)

Horizontal row; indicates number of occupied electron shells.

Alkali metals

Group 1 elements; very reactive, soft metals that form alkaline solutions.

Halogens

Group 7 elements; reactive non-metals that form diatomic molecules.

Noble gases

Group 0 elements; unreactive due to full outer electron shells.

Oxidation

Gain of oxygen or loss of electrons.

Reduction

Loss of oxygen or gain of electrons.

Oxidising agent

Substance that causes another to be oxidised (accepts electrons).

Redox (displacement) reaction

Reaction involving simultaneous oxidation and reduction.

Rust

Hydrated iron(III) oxide formed when iron reacts with oxygen and water.

Galvanising

Coating steel or iron with zinc to prevent rusting.

Sacrificial protection

Attaching a more reactive metal (e.g., zinc) to protect iron from corrosion.

Filtration

Separating an insoluble solid (residue) from a liquid (filtrate) using filter paper.

Crystallisation

Separating a soluble solid from its solution by evaporating solvent until crystals form.

Simple distillation

Separates a solvent from a solution using evaporation and condensation.

Fractional distillation

Separates a mixture of liquids with different boiling points.

Anti-bumping granules

Small glass beads added during distillation to ensure smooth boiling.

Residue

Solid left on the filter paper after filtration.

Filtrate

Liquid that passes through the filter paper during filtration.

Chromatography

Technique to separate substances based on differing solubilities in a solvent.

Baseline (chromatogram)

Pencil line where sample spots are placed; must stay above solvent level.

Solvent front

Highest point reached by the solvent on the chromatogram.

Rf value

Distance travelled by spot ÷ distance travelled by solvent; ranges 0.00–1.00.

Halide

Compound containing a halogen bonded to a metal.

Reactivity trend – Group 1

Reactivity increases down the group; melting points decrease.

Reactivity trend – Group 7

Reactivity decreases down the group; melting points increase.

Displacement of halogens

More reactive halogen displaces less reactive halogen from its compound (e.g., Cl₂ + KI → KCl + I₂).

Hydrogen test

Apply a burning splint; hydrogen burns with a squeaky pop.

Universal indicator in alkali

Turns purple/violet in strongly alkaline solutions (e.g., NaOH from Na + H₂O).

Solubility curve

Graph showing how solubility of a substance changes with temperature.

Pencil (chromatography)

Used to draw baseline because graphite is insoluble and will not run.

Iron rusting requirements

Requires both oxygen and water to produce hydrated iron(III) oxide.