Acid | A chemical that produces hydrogen ions when it dissolves in water. |
Activation energy | The minimum amount of energy required for a given chemical reaction to take place. |
Alkali | A base that is soluble in water. |
Alloy | A metallic substance madeby comtwo or more metals. |
Anhydrous | An anhydrous substance does not contain any water. |
Anode | Electrode where oxidation occurs. |
Atomic number | The number of protons in a nucleus, symbol Z (also known as the proton number). |
Bases | Chemicals which react with acids to neutralise them. |
Bond energy | The energy required to break a particular chemical bond. |
Catalyst | A substance that incthe rate of another reaction but is not used up or changed itself. |
Cathode | Electrode where reduction occurs |
Chromatography | A technique for separatia mixture of substances using a stationary and a moving phase. |
Collision theory | An explanation of chemical reactions in terms of thereactant particlescolliding with sufficient energy for a reaction to take place. |
Covalent bond | The chemical bond made when atoms join together by sharing electrons. |
Dissociation | The separation of a chetwo or more simpler substances, or of a molecule into atoms or ions. |
Electrolyte | A substance that conducts electricity when molten or in aqueous sol. |
Electrolysis | Using eleto drive a redox reaction. |
Electronic structure | The arrangement of electrons in an atom. |
Empirical formula | A chemical formula showing the ratio of the number of atoms in a compound. |
Endothermic | A reaction that involves a net absorption of energy. |
Equilibrium | The point at which a reversible reaction happens at exactly the same rate in both directions. |
Exothermic | A reaction that involves a net release of energy. |
Fractional distillation | A way of separating a mixture of substances by their different boiling points. |
Giant covalent structures | Giant structures held together by many covalent bonds which give them high melting points and hardness, e.g. diamond and quartz. |
Hydrated | A hydrated subwater. |
Hydrocarbon | A compound made of only carbon and hydrogen. |
Indicator | A chemical that changes colour according to the pH of the solution it is in. |
Intermolecular forces | Forces of attraction between molecules. |
Ionic bond | A chemical bond made when one atom gives up one or more electrons to another atom. |
Ionisation | Any process in which atoms become charged by gaining or losing electrons. |
Isotopes | Atoms of the same element which have different numbers of neutrons. |
Mass number | The total number of protons and neutrons in an atom (symbol A). |
Mass spectrometer | An instrument used to measure the masses of atoms and molecules. |
Mole | A unit of measurement for the amount of substance, equ6.×1023particles. |
Molecular formula | A formula that shows the numbers of the different kinds of atoms in a molecule. |
Oxidation | The loss of electrons. |
Ozone layer | The layer of ozone gas in the Earth’s atmosphere that absorbs ultraviolet radiation. |
Percentage yield | The percentage of product formed in a chemical reaction as a perofthe maximum possible amount of product that could be formed. |
Polymer | A substance consisting of very large molecules made of smaller molecules called monomers. |
Proton acceptor | The modern definition of an alkali. |
Proton donor | The modern definition of an acid. |
Redox | A reaction where electrons are lost by one substance and gained by another. |
Reduction | The gain of electrons. |
Relative atomic mass | The mass of an atom compared with an atom of 12. |
Reversible reaction | A reaction in which the products react together to produce the original reactants. |
Shells | The region where eleare locatedas they travel around the nucleus of an atom. |
Solubility | The extent to which a solute will dissolve in a sol. |
Thermal decomposition | The splitting up of a substance by heat. |
Titration | A commethod for measuring the amount of substance in a solution. |
Transition metals | The block of metallic elements in the middle of the periodic table. |