CHEMISTRY PAPER 1 KEYWORDS

Element

A substance made of only one type of atom.

Compound

A substance made from two or more elements chemically bonded.

Mixture

Two or more substances not chemically bonded and easily separated.

Isotope

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

Relative Atomic Mass (Ar)

The weighted average mass of an atom of an element compared to 1/12 the mass of carbon-12.

Atomic Number

The number of protons in the nucleus of an atom.

Mass Number

The total number of protons and neutrons in an atom's nucleus.

Ionic Bonding

The electrostatic attraction between oppositely charged ions.

Covalent Bonding

A bond formed when two atoms share a pair of electrons.

Metallic Bonding

The attraction between positive metal ions and a sea of delocalised electrons.

Alloy

A mixture of metals or a metal and another element, designed to have improved properties.

Simple Molecular Substance

A substance made up of molecules containing a few atoms joined by covalent bonds.

Giant Covalent Structure

A large lattice of covalently bonded atoms (e.g., diamond or graphite).

Giant Ionic Lattice

A regular structure of ions held together by strong electrostatic forces.

Mole

The amount of substance containing 6.02 × 10²³ particles (Avogadro’s constant).

Relative Formula Mass (Mr)

The sum of the relative atomic masses of all atoms in a formula.

Concentration

The amount of solute dissolved in a given volume of solution (mol/dm³).

Limiting Reactant

The reactant that is completely used up first, limiting the amount of product formed.

Reactivity Series

A list of elements ordered by their reactivity with water or acid.

Displacement Reaction

A reaction in which a more reactive element displaces a less reactive element from a compound.

Redox Reaction

A reaction involving both reduction (gain of electrons) and oxidation (loss of electrons).

Electrolysis

The breakdown of a substance using electricity.

Anode

The positive electrode where oxidation occurs.

Cathode

The negative electrode where reduction occurs.

Ore

A rock containing enough metal to make it economically worthwhile to extract.

Exothermic Reaction

A reaction that releases energy to the surroundings (temperature increases).

Endothermic Reaction

A reaction that absorbs energy from the surroundings (temperature decreases).

Activation Energy

The minimum amount of energy needed for a reaction to start.

Reaction Profile

A diagram showing the energy levels of the reactants and products in a reaction.