GCSE Science Dictionary

Acid A solution with a pH of less than 7 - a "proton donor"
Activation energy The minimum amount of energy needed to start (or "activate") a reaction.
Addition polymerisation Reaction where many small molecules are joined together to make a long chain molecule and nothing else is produced
Alcohol A homologous series of compounds containing the functional group OH
Alcohol (in Chemistry) A homologous series of compounds containing the functional group OH
Alkali A solution with a pH of more than 7 - a "proton acceptor".
Alkali metal Metals from group 1 in the periodic table that react with water to produce an alkaline solution
Alkane A hydrocarbon that contains only single bonds - a "saturated hydrocarbon"
Alkene A hydrocarbon that contains 1 carbon carbon double bond - an unsaturated hydrocarbon
Alloy A mixture of metals
Ammonia A compound made from nitrogen and hydrogen
Ammonium nitrate A fertiliser made from a neutralisation reaction between ammonia and nitric acid
Anhydrous Describes a substance that does not contain water
aq An abbreviation that stands for "aqueous solution"
Aqueous When something has been dissolved in water
Ar A symbol for relative atomic mass - the relative mass of one atom of an element
Atmosphere The layer of gases above the Earth's surface
Atom The smallest particle of an element that can exist
Atom economy A way to measure how many starting chemicals end up as useful products
Atomic mass See Relative Atomic Mass (use this for your definition)
Atomic number Also known as the proton number, the number of protons in the nucleus of an atom
Atoms The smallest particle of an element
Balanced equation A way to show how many moles of products and reactants are involved in a reaction
Base A compound that will neutralise an acid
Biodegradable A word used to describe a substance that can be broken down by microorganisms
Biodiesel A hydrocarbon fuel made from plant oils that can be burned releasing heat energy
Biofuel A fuel derived from plants
Biogas A gas produced by the breakdown of organic matter in the absence of oxygen. Biogas is a renewable energy source
Bioleaching When bacteria are used to extract metals.
Blast furnace A device used to extract iron from iron oxide
Boiling point The temperature at which a substance turns from a liquid to a gas
Bond A "link" formed between atoms or ions, holding them together in a compound
Bond energy The amount of energy released when a bond is made or the amount of energy required to break a bond
Burette A burette is a long glass tube with a tap at the bottom used to measure volumes of liquids
Calcium carbonate CaCO3, Limestone
Calcium hydroxide Ca(OH)2 (s) also known as slaked lime or Ca(OH)2 (aq) also know as lime water. Both forms are produced by adding water to calcium oxide.
Calcium oxide CaO, or quicklime.
Carbon monoxide A poisonous gas
Carbonate A general name for a compound containing carbon and oxygen
Cast iron Cast iron or pig iron is the iron produced by the blast furnace. It contains carbon which makes it brittle.
Catalyst A chemical that speeds up a reaction
Cement A substance made from limestone and clay; it is used to concrete.
Chemical formula A way to represent how many atoms are in a compound
Chemical reaction A reaction between chemicals (reactants) which produce one or more new substances (products)
Chromatography A technique used to separate dissolved substances e.g. artificial colours in foods
Collision theory For a reaction to occur, the reactants must collide with sufficient energy for a succesful collision.
Combustion Burning something, a reaction with oxygen to release heat energy
Complete combustion When combustion occurs in an excess of oxygen.
Compound A substance made from atoms of different elements joined together by covalent or ionic bonds.
Concentration (mass) The number of grams of solute per cubic decimetre of a solution
Concentration (molar) The number of moles per cubic decimetre of a solution
Concrete An artificial stone made using cement.
Condensation When a gas is cooled to form a liquid
Conductor A substance that allows electricity or thermal (heat energy) to pass through it easily.
Continental drift The process of tectonic plates moving relative to each other
Convection current Convection currents are movements occurring in materials that can flow because of differences in temperature. Between different parts.
Core The part of the Earth's structure nearer to the centre
Corrode When a substance usually a metal reacts with the environment which causes it to break down
Corrosion When a substance usually a metal reacts with the environment which causes it to break down
Covalent When a compound has no free electrons and no free ions
Covalent bond A type of bond formed when atoms "share" electrons
Cracking The breaking up of long chained hydrocarbons to form an Alkene and an Alkane.
Crude oil A mixture of hydrocarbons from fossil fuel.
Crust The outer layer of the Earth, it is solid.
Delocalised electron An electron which is not located in an electron shell but can move between different atoms.
Diamond A form of carbon
Diesel A fossil fuel
Dilute solution A weak form of a solution
Displacement An element which is more reactive can displace a less reactive element.
Distillation A process used to separate a mixture of liquids with different boiling points
Dot and cross diagram Dot and cross diagrams are used to display electrons in ionic or covalent bonding.
Double bond A bond found between carbon atoms in alkenes
Economically viable If a product is worth the expense of making it then the process is economically viable
Electrodes These supply an electric current to a molten or dissolved ionic compound so that electrolysis can occur. The products of electrolysis form at the electrodes.
Electrolysis The process of splitting a compound using electricity
Electrolyte The molten substance or solution where electrolysis occurs.
Electron The negatively charged particle in an atom
Electron arrangement A way to show which shells electrons are in
Electron configuration A way to show which shells electrons are in
Electronic configuration A way to show which shells electrons are in
Electrostatic attractions The attraction of a positive charge to a negative charge.
Element A substance that is made of one type of atom only
Empirical formula the simplest formula of a compound
Emulsifier A substance added to form an emulsion, it stops the mixture from separating
Emulsion A mixture of two liquids in which small droplets of one liquid are spread throughout the other liquid e.g. Oil and water can be mixed with an emulsifier to form an emulsion
End point In a titration the point at which a colour change indicates the change in pH.
Endothermic reaction A chemical reaction that takes in energy from the surroundings often as thermal (heat) energy.
Energy profile A diagram showing the energy of reactants and products in a reaction, the activation energy and shows whether the reaction is endothermic or exothermic
Equilibrium the point in a reversible reaction when the rate of the forward reaction (reactants to products) exactly balances the rate of the reverse reaction.
Ethanol Ethanol is more commonly referred to as alcohol. C2H5OH
Exothermic reaction A chemical reaction that transfers energy to the surroundings often as thermal (heat) energy.
Extraction The process of releasing a metal from its ore
Fermentation A reaction involving yeast that produces carbon dioxide.
Fertiliser A chemical used to help crops to grow
Flammable A substance that catches fire easily
Fossil fuel Coal, oil and gas (remember solid, liquid and gas)
Fossil fuels Coal, oil and gas (remember solid, liquid and gas)
Fraction A part of crude oil that is separated using fractional distillation, the hydrocarbon in each fraction will have similar boiling points
Fractional distillation A process used to separate crude oil into different fractions.
Fullerene A type of carbon structure in the shape of a ball, cage or cylinder

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Chemistry Words