Chemistry Terms

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Term Definition
Acid A substance that can attack metal clothing or the skin. Has a pH of less than 7. They are proton (H+ ion) donators.
Activation Energy The minimum energy needed to start a reaction
Alkali Metal (Definition) Elements in group 1 of the periodic table
Alkali Metal (Example) Lithium (Li). Sodium (Na). Potassium (K)
Alkali It’s solution has a pH of more than 7
Alkane (Definition) A saturated hydrocarbon that has no double bonds between the carbon atoms
Alkane (Example) Ethane
Alkene (Definition) Unsaturated hydrocarbon which contains a double carbon-carbon bond.
Alkene (Example) Ethene
Alloy (Definition) A mixture of metals (and sometimes non metals)
Alloy (Example) Brass – A mixture of Copper and Zinc
Aluminium A low density corrosion-resistant metal used in many alloys
Anhydrous Describes a substance that does not contain water.
Aqueous Solution (Definition) The mixture made by adding a soluble substance to water
Aqueous Solution (Abbreviation In Equations) aq
Atom The smallest part of an element which can be recognised as an element
Atomic Number The number of protons (which equals the number of electrons) in an atom. It is sometimes called the proton number
Atomic Weight The historical term that was used before relative atomic masses were defined in the 20th century.
Base The oxide, hydroxide or carbonate of a metal that forms a salt as a product when it reacts with acid. They are proton (H+ ion) acceptors.
Biodegradable Materials that can be broken down by microorganisms
Biodiesel Fuel for cars made from plant oils
Biofuel Fuel made from animal or plant products
Bioleaching Process of extraction of metals from ores using microorganisms
Blast Furnace The huge reaction vessels used in industry to extract iron from its ore.
Bond Energy The energy needed to break a particular chemical bond
Burette A long glass tube with a tap at one end and markings to show volumes of liquid used to add precisely known amounts of liquids to a solution in a conical flask below it
Calcium Carbonate The main compound found in limestone. It is a white solid whose formula is CaCO
Calcium Hydroxide A white solid made by reacting calcium oxide with water. It is used as a cheap alkali in industry.
Calcium Oxide A white solid made by heating limestone strongly. For example in a lime kiln.
Carbon Monoxide A toxic gas whose formula is CO
Cast Iron The impure iron taken directly from a blast furnace.
Catalyst A substance that increases the rate of a chemical reaction. It is not used or changed in the reaction.
Cement A building material made by heating limestone and clay.
Chromatography The process whereby small amounts of dissolved substances are separated by running a solvent along a material such as absorbent paper.
Collision theory An explanation of chemical reactions that says that particles colliding have to have a sufficient amount of energy in order for a reaction to take place.
Compound A substance made when two or more elements are chemically bonded together. For example water (H2O) is a compound made from hydrogen and oxygen.
Concrete A building material made by mixing cement sand and aggregate (crushed rock) with water.
Convection Current The circular motion of matter caused by heating in fluids.
Copper-Rich Ore Rock that contains a high proportion of a copper compound.
Core The centre of the Earth.
Covalent Bonding The attraction between two atoms that share one or more pairs of electrons.
Cracking The reaction used in the oil industry to break down large hydrocarbons into smaller more useful ones. This occurs when the hydrocarbon vapour is either passed over a hot catalyst or mixed with steam and heated to a high temperature.
Crust The outer solid layer of the Earth.
Delocalised Electron Bonding electron that is no longer associated with any one particular atom.
Displace When one element takes place of another in a compound.
Distillation Separation of a liquid from a mixture by evaporation followed by condensation.
Dot And Cross Diagram A drawing to show the arrangement of the outer shell electrons only of the atoms or ions in a substance.
Double Bond A strong covalent bond made by sharing 2 pairs of electrons.
Electrolyte A liquid containing free-moving ions that is broken down by electricity in the process of electrolysis.
Electron A tiny particle with a negative charge. Electrons orbit the nucleus in atoms or ions.
Electronic Structure A set of numbers to show the arrangement of electrons in their shells (or energy levels). For example the electronic structure of a potassium atom is 2,8,8,1.
Element A substance made up of only one type of atom. It cannot be broken down chemically into any simpler substance.
Empirical Formula The simplest ratio of elements in a compound.
Emulsifier A substance which helps keep immiscible liquids (for example oil and water) mixed so that they do not separate out into layers.
Emulsion A mixture of liquids that do not dissolve in each other.
End Point The point in a titration where the reaction is complete and titration should stop.
Ester When a carboxylic acid is reacted with an alcohol
Endothermic A reaction that takes in energy from the surroundings
Energy Level An area in an atom round its nucleus where the electrons are found.
Equilibrium The point in a reversible reaction in which the forward and backward rates of reaction are the same. Therefore the amounts of substances present in the reacting mixture remain constant.
Ethene An alkene with the formula C2H4
Exothermic A reaction that gives out energy to the surroundings.
Fermentation The reaction in which the enzymes in yeast turn glucose into ethanol and carbon dioxide
Flammable Easily ignited and capable of burning rapidly.
Fraction Hydrocarbons with a similar boiling point separated from crude oil
Fractional Distillation A way to separate liquids from a mixture of liquids by boiling off the substances at different temperatures and then condensing and collecting the liquids
Fullerene Form of the element carbon that can form a large cage-like structure based on hexagonal rings of carbon atoms
Functional Group An atom or group of atoms that give organic compounds their characteristic reactions.
Gas Chromatography The process of separating the components in a mixture by passing the vapours through a column and detecting them as they leave the column at different times.
Giant Covalent Structure A huge 3D network of covalently bonded atoms (e.g. the giant lattice of carbon atoms in diamond or graphite).
Giant Lattice A huge 3D network of atoms or ions (e.g. the giant ionic lattice in sodium chloride).
Giant Structure Giant Lattice
Global Dimming The reflection of sunlight by tiny solid particles in the air.
Global Warming The increasing of the average temperature of the Earth.
Gradient Change In Y / Change In X
Group All the elements in each column (labelled 1 to 7 and 0) down the Periodic table.
Hard Water Water in which is it is difficult to form a lather with soap. It contains Calcium and/or Magnesium ions which react with soap to produce scum.
Hardening The process of reacting plant oils with hydrogen to raise their melting point. This is used to make spreadable margarine.
Homologous Series A group of related organic compounds that have the same functional group. For example the molecules of the homologous series of alcohols all contain the -OH group.
Hydrated Describes a substance that contains water in its crystals. For example Hydrated Copper Sulfate.
Hydrocarbon A compound containing only hydrogen and carbon.
Hydrogenated Oil Oil which has had hydrogen added to reduce the degree of saturation in the hardening process to make margarine.
Hydrophilic The water-loving part of an emulsifier molecule.
Hydrophobic The water-hating hydrocarbon part of an emulsifier molecule.
Incomplete Combustion When a fuel burns in insufficient oxygen producing carbon monoxide as a toxic product.
Inert Unreactive.
Intermolecular force The attraction between the individual molecules in a covalently bonded substance.
Ion A charged particle produced by the loss or gain of electrons.
Ion-Exchange Column A water softener which works by replacing calcium and magnesium ions with sodium or hydrogen ions. This removes the hardness.
Ionic Bonding The electrostatic force of attraction between positively and negatively charged ions
Isotope Atom that has the same number of protons but a different number of neutrons. It has the same atomic number but a different mass number
Limewater The common name for calcium hydroxide solution
Macromolecule Giant covalent structure
Mantle The layer of the Earth between the crust and the Core.
Mass Number The total number of protons and neutrons in an atom.
Mass spectrometer A machine that can be used to analyse small amounts of a substance to identify it and to find its relative molecular mass.
Mixture When some elements or compounds are mixed together and intermingle but do not react together (i.e. no new substance is made). A mixture is not a pure substance.
Mole The amount of substance in the relative atomic or formula mass of a substance in grams.
Molecular formula The chemical formula that shows the actual numbers of atoms in a particular molecule (e.g. C H^).
Molecular Ion peak The peak on the mass spectrum of a substance which tells us the relative molecular mass of the substance. The peak is produced by the heaviest positive ion shown on the mass spectrum.
Monomers Small reactive molecules that react together in repeating sequences to form a very large molecule (a polymer).
Mortar A building material used to bind bricks together. It is made by mixing cement and sand with water.
Nanometre 1.0 × 10-9 Metres
Nanoscience The study of very tiny particles or structures between 1 and 100 nanometres in size
Neutral (pH) A solution with a pH value of 7 that is neither acidic nor an alkaline
Neutral (Other) Something that carries no overall electrical charge – neither positively nor negatively charged.
Neutralisation When an acid reacts with a base they cancel each other out, and forms a salt and water.
Neutron A dense particle found in the nucleus of an atom. It is electrically neutral. They have no overall charge.
Nitrogen Oxides Gaseous pollutants given off from motor vehicles. This is a cause of acid rain.
Nucleus The very small and dense central part of an atom which contains protons and neutrons.
Ore Rock which contains enough metal to make it economically worthwhile to extract the metal.
Oxidation The reaction when oxygen is added to a substance (or when electrons are lost).
Oxidised A reaction where oxygen is added to a substance (or when electrons are lost from a substance).
Particulate Small solid particle given off from motor vehicles as a result of incomplete combustion of its fuel.
Percentage Yield The actual mass of product collected in a reaction divided by the maximum mass that could have been formed in theory multiplied by 100.
Periodic table An arrangement of elements in the order of their atomic numbers forming groups and periods.
Permanent hard water Hard water whose calcium and/or magnesium ions are not removed when the water is boiled thus remaining hard.
pH scale A number that shows how strongly acidic or alkaline a solution is. Acids have a pH value of less than 7 (pH 1 is strongly acidic). Alkalis have a pH value above 7 (pH 14 is strongly alkaline). A neutral liquid has a pH value of 7.
Phytomining The process of extraction of metals from ores using plants.
Pipette A tube used to measure accurate volumes of liquids.
Polymer A substance made from very large molecules made up of many repeating units. For example Poly(ethene).
Polymerisation The reaction of monomers to make a polymer.
Precipitate An insoluble solid formed by a reaction taking place in solution.
Product A substance made as a result of a chemical reaction.
Propene An alkene with the formula C3H8.
Proton A tiny positive particle found inside the nucleus of an atom.
Reactant A substance we start with before a chemical reaction takes place.
Reactivity Series A list of elements in order of their reactivity. The most reactive element is put at the top of the list.
Reduction A reaction in which oxygen is removed (or electrons are gained).
Relative Atomic Mass (Definition) The average mass of the atom of an element compared with carbon-12 (which is given a mass of exactly 12). The average mass must take into account the proportions of the naturally occurring isotopes of the element.
Relative Atomic Mass (Symbol) Ar
Relative Formula Mass (Definition) The total of the relative atomic masses added up in the ratio shown in the chemical formula of a substance.
Relative Formula Mass (Symbol) Mr
Retention Time The time it takes a component in a mixture to pass through the column during gas chromatography
Reversible Reaction A reaction in which the products can re-Form the reactants.
Salt A compound formed when some or all of the hydrogen in an acid is replaced by a metal (or by an Ammonium ion). For example Potassium Nitrate – KNO3 (from nitric acid).
Saturated Hydrocarbon A hydrocarbon that contains as many hydrogen atoms as possible in each molecule.
Scale (Limescale) the insoluble substance formed when temporary hard water is boiled.
Scum The precipitate formed when soap reacts with calcium and/or magnesium oxide ions in hard water.
Shape Memory Alloy Mixture of metals which respond to changes in temperature.
Shell An area in an atom round its nucleus where the electrons are found.
Smart Polymer Polymers that change in response to changes in their environment.
Smelting Heating a metal ore in order to extract its metal.
Soapless Detergent A cleaning agent that does not produce scum when used with hard water.
Soft Water Water containing no dissolved calcium and/or magnesium salts so it easily forms a lather with soap.
Stainless Steel A chromium-nickel alloy of steel which does not rust.
State Symbol The abbreviations used in balanced symbol equations to show if reactants and products are solid (s). Liquid (1). Gas (g) or dissolved in water (aq).
Steel An alloy of iron with small amounts of carbon or other metals such as nickel and chromium added.
Strong Acids Acids that ionise completely in aqueous solutions.
Sulfur Dioxide A toxic gas whose formula is SO2. It causes acid rain.
Tectonic Plates The huge stabs of rock that make up the Earth’s crust and the top part of its mantle.
Temporary Hard Water Hard water which is softened when it is boiled.
Thermal Decomposition The breakdown of a compound by heat.
Thermosetting Polymer Polymer that can form extensive cross-linking between chains. This results in rigid materials which are heat-resistant.
Thermosoftening Polymer Polymer that forms plastics which can be softened by heat. It is then remoulded into different shapes as they cool down and set.
Titanium A shiny and corrosion-resistant metal used to make alloys.
Titration A method for measuring the volumes of two solutions that react together.
Transition Element Element from the central block of the periodic table. It has typical metallic properties and forms a coloured compound.
Transition Metal Element from the central block of the periodic table. It has typical metallic properties and forms a coloured compound.
Universal Indicator A mixture of indicators which can change through a range of colours depending on the pH of a solution. Its colour is matched to a pH number using a pH scale. It shows how strongly acidic or alkaline liquids and solutions are.
Unsaturated Hydrocarbon A hydrocarbon whose molecules contain at least one carbon-carbon double bond.
Unsaturated Oil Plant oil whose molecules contain at least one carbon-carbon double bond
Vegetable Oil Oil extracted from plants
Viscosity The resistance of a liquid to flowing or the “thickness” or a resistance of a liquid to pouring
Weak Acids Acids that do not ionise completely in aqueous solutions.
Yield The amount of product obtained in a reaction.