Edexcel International GCSE (9-1) Chemistry Unit 1 & 2 Vocabulary

Comprehensive vocabulary flashcards covering the principles of chemistry, inorganic chemistry, physical chemistry, and organic chemistry concepts as outlined in the Edexcel IGCSE Student Book.

Sublimation

The conversion of a solid directly into a gas without involving any liquid in the process.

Diffusion

The spreading out of particles from an area of high concentration to an area of low concentration.

Solute

The substance that dissolves in a liquid.

Solvent

The liquid in which a solute dissolves.

Saturated Solution

A solution which contains as much dissolved solid as possible at a particular temperature.

Solubility

The maximum mass of solute that dissolves in $100\,g$ of solvent at a particular temperature.

Element

A substance that cannot be split into anything simpler by chemical means and contains only one type of atom.

Compound

A substance formed when two or more elements chemically combine in fixed proportions.

Mixture

A combination of substances that are not chemically joined and can be separated by physical means.

Isotopes

Atoms of the same element which have the same atomic number but different mass numbers (different numbers of neutrons).

Relative Atomic Mass ($A_r$)

The weighted average mass of the isotopes of an element, measured on a scale where a carbon-12 atom has a mass of exactly $12$.

Mole (mol)

The unit for the amount of a substance; one mole contains the Avogadro constant ($6.02 \times 10^{23}$) of particles.

Empirical Formula

The formula showing the simplest whole number ratio of the atoms present in a compound.

Molar Volume

The volume occupied by one mole of any gas at room temperature and pressure; approximately $24\,dm^3$ ($24000\,cm^3$).

Ionic Bonding

The strong electrostatic attraction between positive and negative ions.

Covalent Bond

The strong electrostatic attraction between the nuclei of two atoms and a shared pair of electrons.

Metallic Bonding

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

Electrolysis

The chemical change caused by passing an electric current through a compound that is either molten or in solution.

Oxidation

The gain of oxygen or the loss of electrons.

Reduction

The loss of oxygen or the gain of electrons.

Halogens

The Group 7 elements (Fluorine, Chlorine, Bromine, Iodine, Astatine) which exist as diatomic molecules.

Hydrocarbon

A compound made up of hydrogen and carbon atoms only.

Activation Energy

The minimum amount of energy required for a collision between particles to result in a chemical reaction.

Catalyst

A substance that increases the rate of a reaction by providing an alternative pathway with a lower activation energy, without being used up itself.

Dynamic Equilibrium

A state in a sealed container where the forward and reverse reactions occur at the same rate and concentrations remain constant.