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IGCSE Chemistry Glossary
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- 1AcetyleneA gas (formula C²H²) used as a fuel, for example in the oxy-acetylene torch
- 2Acid RainRain that is acidic because gases such as sulfur dioxide are dissolved in it (from burning fossil fuels)
- 3Acidic SolutionHas a pH less than 7; an acidic solution contains H+ ions
- 4Acid FermentationThe process in which bacteria convert ethanol to ethanoic acid
- 5Addition ReactionWhere a molecule adds onto an alkene, and the C=C double bond of the alkene changes to a single bond
- 6Addition PolymerisationWhere small molecules join to form a very large molecule, by adding on at double bonds
- 7AlcoholsA family of organic compounds, similar to the alkanes but with the OH functional group; ethanol is example
- 8AlkaliA soluble base; for example sodium hydroxide
- 9Alkali MetalsThe group I elements of the periodic table
- 10Alkaline Earth MetalsThe group II elements of the periodic table
- 11Alkaline SolutionHas a pH above 7; alkaline solutions contain OH- ions
- 12AlkanesA family of saturated hydrocarbons with the general formula CnH2n+2; 'saturated' means they have only single C-C bonds
- 13AlkenesA family of unsaturated hydrocarbons with the general formula CnH2n ; their molecules contain carbon=carbon double bond
- 14AllotropesDifferent forms of an element; diamond and graphite are allotropes of carbon
- 15AlloyA mixture where at least one other substance is added to a metal, to improve its properties; the other substance is often a metal too (but not always)
- 16AmphotericCan be both acidic and basic in its reaction; for example aluminium oxide is an amphoteric oxide
- 17AnionAnother name for negative ion
- 18AnodeThe positive electrode of a cell
- 19AquiferUnderground rocks holding a large volume of water; it can be pumped out to give a water supply
- 20AtmosphereThe layer of gases around the Earth; here at the Earth's surface, we call it air
- 21AtomsElements are made up of atoms. which contain protons, neutrons and electrons
- 22Avogadro ConstantThe number of particles in one mole of an element or compound; it is 6.02 x 10^23
- 23Back ReactionThe reaction in which the product breaks down again, in a reversible reaction
- 24BacteriaTiny organisms, some of which can cause disease; other break down dead plant and animal material
- 25Balanced EquationA chemical equation in which the number of each type of atom is the same on both sides of the arrow
- 26BaseA metal oxide or hydroxide; a base will neutralise an acid, to form a salt and water
- 27BatteryA portable electrical cell; for example a torch battery
- 28BiodegradableWill decay naturally in the soil, with the help of bacteria
- 29BiopolymerA polymer made by bacteria
- 30Blast FurnaceThe chemical plant in which iron is extracted from its ore, iron(III) oxide
- 31BoilingThe change from a liquid to a gas, which takes place at the boiling point
- 32Boiling PointThe temperature at which a substance boils
- 33Bond EnergyThe energy needed to break a bond, or released when the bond is formed; it is given in kilojoules (kJ) per mole
- 34BondingHow the atoms are held together in an element or compound; there are three types of bonds: ionic, covalent, and metallic
- 35BrittleBreaks up easily when struck
- 36BrineThe industrial name for a concentrated solution of sodium chloride in water; it can be made by dissolving rock salt
- 37BuretteA piece of laboratory equipment for delivering a measured volume of liquid
- 38BurningAn exothermic chemical reaction in which the reactant combines with oxygen to form an oxide; also called combustion
- 39Carbon CycleThe way carbon moves non-stop between the atmosphere, living things, the land, and the ocean; it moves in the form of carbon dioxide
- 40Carboxylic AcidsA family of organic acids, which have the COOH functional group; ethanoic acid is an example
- 41Cast IronIron from the blast furnace that is run into molds to harden; it contains a high % of carbon, which makes it brittle
- 42CatalystA substance that speeds up a chemical reaction, without itself being used up in the process
- 43Catalytic ConverterA device in a car exhaust, in which catalysts are used to convert harmful gases to harmless ones
- 44Catalytic CrackingWhere large molecules of hydrocarbons are split up into smaller ones, with the help of catalyst
- 45CathodeThe negative electrode of an electrolysis cell
- 46CationAnother name for a positive ion
- 47Cell (Biological)The building blocks for animals and plants
- 48Cell (Electrical)A device that converts chemical energy to electrical energy
- 49CementA substance used in building, made from limestone and clay
- 50CeramicA hard, unreactive material that can withstand high temperatures, made by baking clay in a kiln; ceramics are non-conductors
- 51ChalkA rock made of calcium carbonate
- 52Change of StateA change in the physical state of a substance - for example from solid to liquid, or liquid to gas
- 53Chemical ChangeA change in which a new chemical substance forms
- 54Chemical EquationUses chemical symbols to describe a chemical reaction in a short way
- 55Chemical ReactionA process in which chemical change takes place
- 56ChromatogramThe paper showing the separated coloured substances, after paper chromatography has been carried out
- 57Climate ChangeHow climates around the earth are changing, because of the rise in average air temperatures
- 58CoagulantA substance that will make small particles stick together; coagulants are used in cleaning up water, ready for piping to homes
- 59CokeA form of carbon made by heating coal
- 60CombinationWhere two or more substances react to form a single substance
- 61CombustibleCan catch fire and burn very easily
- 62CombustionAnother name for burning
- 63Compound FertiliserIt provides nitrogen, potassium and phosphorus for plants
- 64Compound IonAn ion containing more than one element; for example the nitrate ion NO3-
- 65CompoundA substance in which two or more elements are chemically combined
- 66ConcentrationTells you how much of one substance is dissolved in another; usually given as grams or moles per dm^3
- 67CondensationThe physical change in which a gas turns into a liquid on cooling
- 68Condensation PolymerisationWhere molecules join to make very large molecules, by elimenating small molecules (such as water molecules)
- 69CondenserA piece of laboratory equipment used to cool a gas rapidly, and turn it into a liquid
- 70ConductorA substance that allows heat or electricity to pass through it easily
- 71Contact ProcessThe industrial process for making sulfuric acid
- 72CorrosionWhere a substance is attacked by air or water, from the surface inwards; the corrosion of iron is called rusting
- 73Covalent BondThe chemical bond formed when two atoms share electrons
- 74Covalent CompoundA compound made of atoms joined by covalent bonds
- 75CrackingReactions in which long-chain hydrocarbon molecules are broken down to shorter, more useful molecules
- 76Cross-linkingThe chemical bonds between the long-chain molecules in some polymers, that hold the chains together
- 77Crude OilThe fossil fuel formed over millions of years from the remains of tiny sea plants and animals; it is also called petroleum
- 78CrystallisationThe process in which crystal form, as a saturated solution cools
- 79Decomposition ReactionWhere a substance breaks down to give two or more products
- 80DenatureTo destroy the structure of an enzyme by heat, or a change in pH
- 81DegradeableWill break down naturally (for example through the action of bacteria)
- 82DensityTells you how 'heavy' something is; the density of a substance is its mass per unit volume; for water it is 1g/cm3
- 83DiatomicA substance is called diatomic if its molecules contain two atoms joined by a covalent bond
- 84DiffusionThe process in which particles mix by colliding randomly with each other, and bouncing off in all direction
- 85Displacement ReactionA reaction in which a more reactive element takes the place of a less reactive one, in a compound
- 86DissolvingThe process in which a soluble substance forms a solution
- 87DistillationSeparating a liquid from a mixture by boiling it off, then condensing it
- 88Double bondA covalent bond in which two atoms share two pairs of electrons
- 89DuctileCan be drawn out into a wire; for example copper is ductile
- 90Dynamic EquilibriumWhere forward and back reactions take place at the same rate, so there is no overall change
- 91ElectrodesThe conductors used to carry current into and out of an electrolyte; they could be graphite rods, for example
- 92ElectrolysisThe process of breaking down a compound by passing a current through it
- 93ElectrolyteThe liquid through which the current is passed, in electrolysis; the current is carried by ions in the electrolyte
- 94Electron Distribution / ConfigurationHow the electrons in an atom are arranged in shells (2 + 8 + ......)
- 95Electron ShellsThe different energy levels which electrons occupy, around the nucleus
- 96ElectronsThe particles with a charge of 1- and almost no mass, in an atom
- 97ElectroplatingCoating one metal with another, using electrolysis
- 98ElementA substance that cannot be split into anything simpler, in a chemical reaction
- 99Empirical FormulaShows the simplest ratio in which the atoms in a compound are combined
- 100EndothermicTakes in energy from the surroundings
- 101EnzymesProteins made by living cells, that act as biological catalysts
- 102EquationIt uses symbols to describe a chemical reaction (but a word equation uses just words)
- 103EquilibriumThe state where the forward and back reactions are taking place at the same rate, in a reversible reaction; so there is no overall change
- 104EsterA compound formed when an alcohol reacts with carboxylic acid; ester often smell of fruit or flowers
- 105EvapourationThe physical change where a liquid turns to a gas at a temperature below its boiling point
- 106ExothermicGives out energy
- 107ExtractTo remove a metal from its ore
- 108FermentationThe process in which the enzyme in yeast break down sugars, to form ethanol and carbon dioixde
- 109FertilisersSubstances added to soil to help crops grow well
- 110FilteringSeparating solids from liquids by pouring the mixture through filter paper
- 111FiltrateThe liquid obtained from filtration (after the solid has been removed)
- 112FlammableBurns easily
- 113Flue Gas DesulfurisationThe removal of sulfur dioxide from the waste gases at power stations, to stop it getting into the atmosphere
- 114FormulaUses symbols and numbers to tell you what elements are in a compound, and the ratio in which they are combined
- 115Forward ReactionThe reaction in which the product is made, in a reversible reaction
- 116Fossil FuelsPetroleum (crude oil), natural gas, and coal; they are called fossil fuels because they were formed from the remains of living things, millions of years ago
- 117Fractional DistillationA method used to separate two or more liquids that have different boiling points
- 118FractionsThe different groups of compounds that a mixture is separated into, by fractional distillation; fractions are collected one by one
- 119FreezingThe change from liquid to solid, that occurs at the freezing point (= melting point)
- 120FuelA substance we use to provide energy; most fuels are burned to release their energy (but nuclear fuels are not)
- 121Functional GroupThe part of the molecule of an organic compound, that largely dictates how it reacts; for example the OH group in molecules of the alcohol family
- 122GalvanisingCoating iron with zinc, to prevent the iron from rusting
- 123Giant StructureWhere a very large number of atoms or ions are held in a lattice by strong bonds; metals, diamond and ionic solids such as sodium chloride are all giant structures
- 124Global WarmingThe rise in average temperature taking place around the world; many scientists believe that carbon dioxide (from burning fossil fuels) is the main cause
- 125Greenhouse GasA gas in the atmosphere that traps heat, preventing its escape into space; carbon dioxide and methane are examples
- 126GroupA column of the Periodic Table; elements in a group have similar properties
- 127Haber ProcessThe process for making ammonia from nitrogen and hydrogen, in industry
- 128Half-equationAn equation that shows the reaction taking place at an electrode
- 129HalogensThe Group VII elements of the Periodic Table
- 130Heating CurveA graph that showing how the temperature of a substance changes on heating, while it goes from solid to liquid to gas
- 131Homologous SeriesA family of organic compounds, that share the same general formula and have similar properties
- 132HydratedHas water molecules built into its crystal structure; for example copper (II) sulfate: CuSO4 . 5H2O
- 133HydrocarbonA compound containing only carbon and hydrogen
- 134Hydrogen Fuel CellIt uses the reaction between hydrogen (from a tank), and oxygen (from the air), to give an electric current
- 135HydrolysisThe breaking down of a compound by reaction with water
- 136HypothesisA statement you can test by doing an experiment and taking measurements
- 137Incomplete CombustionThe burning of fuels in a limited supply of oxygen; it gives carbon monoxide instead of carbon dioxide
- 138IndicatorA chemical that shows by its colour whether a substance is acidic or alkaline
- 139InertDoes not react (except under extreme conditions)
- 140Inert ElectrodeIs not changed during electrolysis; all it does is conduct the current
- 141In ExcessMore than is needed for a reaction; some will be left at the end
- 142InsolubleDoes not dissolve in a solvent
- 143InsulatorA poor conductor of heat or electricity
- 144Intermolecular ForcesForces between molecules
- 145IonA charged atom or groups of atoms formed by the gain or loss of electrons
- 146Ionic BondThe bond formed between ions of opposite charge
- 147Ionic CompoundA compound made up of ions, joined by ionic bonds
- 148Ionic EquationShows only the ions that actually take part in a reaction, and ignores any other ions present; the other ions are called spectators ions
- 149IsomersCompounds that have the same formula, but a different arrangement of atoms
- 150IsotopesAtoms of the same element, that have different numbers of neutrons
- 151LatticeA regular arrangement of particles
- 152LimeThe common name for calcium oxide
- 153LimewaterA solution of the slightly soluble compound calcium hydroxide, which is used to test for carbon dioxide
- 154Locating AgentUsed to show up colourless substances, in chromatography; it reacts with them to give coloured substance
e.g. : ninhydrin - 155MacromoleculeA very large molecule; for example a molecule in a polymer
- 156MalleableCan be bent or hammered into shape
- 157Mass SpectrometerAn instrument used to find the masses of atoms and molecules
- 158Melting PointThe temperature at which a solid substance melts
- 159MeltingThe physical change from a solid to a liquid
- 160MetalAn element that shows metallic properties (for example conducts electricity, and forms positive ions)
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- GCSE and IGCSE (Chemistry) GCSEs Fichas sobre IGCSE Chemistry Glossary, creado por Jade Lai el 19/11/2014.
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- Jade Lai
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