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EARLSTON HIGH SCHOOL HIGHER CHEMISTRY GLOSSARY CA/2/AW6523/Chem-O UNIT 1 Activation energy ENERGY MATTERS The minimum KE required by colliding molecules to form an activated complex. Activated complex An unstable arrangement of atoms formed at the maximum of the potential energy barrier during a reaction. Active site The point on the surface of the catalyst where adsorption occurs. Adsorption Bonding onto the surface of a substance (eg a catalyst). Anomalous Unusual – not following the expected trend. Avogadro constant The number of formula units in 1 mole (6.02 x 1023). Catalyst A substance which increases the rate of reaction and is recovered unchanged at the end. Catalyst poisoning A substance is preferentially absorbed onto the surface of the catalyst preventing adsorption by the substrate eg lead poisons the catalyst in catalytic converters. Catalytic converter Fitted to cards to catalyse the conversion of poisonous carbon monoxide and oxides of nitrogen to CO2 and N2. Collision theory A theory used to explain the effects of concentration and surface area on reaction rates. Contact process Industrial process to manufacture sulphuric acid using the catalyst vanadium (V) oxide. Covalent bond Atoms are held together by electrostatic forces of attraction between positively charged nuclei and negatively charged shared electrons. Covalent network A giant lattice of covalently bonded atoms. Delocalised Not attached to one particular atom. Dipole Results from charge separation within particles – particles have oppositely charged ends. Discrete Separate. CA/2/AW6523/Chem-O Electrolysis Production of an element from a compound, either molten or in a solution, by passing electricity through it. Electronegativity Attraction of atoms for bonding electrons. Values increase across a period and decrease down a group. Elementary entity Could refer to atoms, molecules, ions, ion pairs, electrons or other particles. Avogadro’s number of them in a mole. Endothermic Heat is taken in during the reaction. ∆H is positive. Energy distribution diagrams Diagrams to show the kinetic energy distributed throughout a number of particles. Enthalpy change (∆H) The heat of reaction or the difference in energy between products and reactants in kilojoules per mole can be calculated using cm ∆T. Enthalpy of combustion The enthalpy change when one mole of a substance burns completely in oxygen. Enthalpy of neutralisation Energy change when one mole of water is produced in a neutralisation reaction. Enthalpy of solution Energy change when one mole of a substance dissolves completely in water. Enzyme A biological catalyst. Catalyse reactions taking place in living cells and used in many industrial processes. Excess There is more than enough of one reactant so some of it remains unchanged. Exothermic Heat is given out during the reaction. ∆H is negative. First ionisation enthalpy Energy required to remove one electron from each atom in a mole of atoms in the gaseous state. Fullerenes Recently discovered forms of carbon in the form of molecular balls (bucky balls) or tubes. Group A column of the periodic table. Haber Process Catalytic conversion of nitrogen and hydrogen to ammonia using iron as catalyst. Heterogeneous In a different physical state. CA/2/AW6523/Chem-O Homogeneous In the same physical state. Hydration of ions Attractive forces between a charged ions and polar water molecules. Hydrogen bonding Intermolecular electrostatic attractions found in compounds containing hydrogen bonded to an atom with a strong attraction for bonding electrons (N.F.O.Cl.). Stronger than other intermolecular bonds but weaker than covalent bonds. Inhibitor Substance used to slow down a reaction eg antioxidants in rubber. Intermolecular forces Forces of attraction between atoms or molecules such as van der Waals forces or polar attractions, including hydrogen bonds. Invertase Enzyme which catalyses the conversion of sucrose to glucose and fructose. Ionic compounds Compound formed between elements widely separated in the periodic table. Ionic lattice A giant lattice structure of oppositely charged ions electrostatically attracted to each other. Mendeleev Russian scientist who arranged elements in order of increasing atomic masses in conjunction with similar chemical properties, leaving gaps for yet to be discovered elements. Metallic bonding Electrostatic attraction of a lattice of positively charged ions and delocalised outer electrons. Miscible Can be mixed to form a homogeneous substance. Molar volume The volume occupied by 1 mole of a substance. It is the same for all gases at the same temperature and pressure. Mole The amount of a substance which contains as many formula units as there are C atoms in 12g of carbon-12. Monatomic Discrete atoms held together by van der Waals’ forces. Period A row across the periodic table. CA/2/AW6523/Chem-O Permanent diple-permanent dipole interactions Additional electrostatic forces of attraction between polar molecules – stronger than van der Waals’ forces. Photochemical reaction Reaction in which light energy increases the number of particles with energy greater than the activation energy. Polar Bonds Caused by a difference in electronegativity between covalently bonded atoms. Atoms become partially charged. Polar molecules Contain polar bonds which are not symmetrically opposed. Molecule has a permanent dipole. Polarity The charge separation – depends on electronegativity differences. Rate The change in concentration (or mass/volume) of reactant or product in unit time (eg mols/l/s). Reciprocal The inverse of eg the reciprocal of t = 1/t. Screening effect Shielding of the outer electrons from the positive nuclear charge by the inner shell electrons. Specific heat capacity of water (c) Energy (kJ) required to raise the temperature of 1 Kg of water 1oC. Stoichiometry Relative quantities of substances involved in reactions. Sublimation Change directly from a solid to a gas. Substrate The reactant which interacts with the catalyst in a reaction. Temperature A measure of the average kinetic energy of the molecules of a substance. Van der Waals’ forces Forces of attraction between atoms or molecules which are much weaker than other forms of bonding. They result from electrostatic attraction between temporary dipoles caused by movement of electrons in atoms and molecules. Bigger particles have stronger forces. CA/2/AW6523/Chem-O UNIT 2 Addition polymers THE WORLD OF CARBON Made from unsaturated monomers by addition polymerisation eg polythene (polyethene) from ethane. Addition reaction Addition of atoms or groups of atoms to alkenes by opening up the double bond, eg hydrogenation, bromination, hydration. Alcohols Substances containing the hydroxyl functional group. Produced by catalytic hydration of alkenes or by fermentation of carbohydrates. Aldehydes Group of substances containing –CHO group. Produced by oxidation of primary alcohols eg using acidified dichromate (yellow to blue colour change seen). Oxidised to carboxylic acids using acidified dichromate or Fehlings/Benedict’s (blue to red colour change seen). Alkanals A homologous series of alcohols based on the corresponding parent alkanes. Alkanones A homologous series of ketones based on the corresponding parent alkanes. Alkenes Hydrocarbons with general formula CnH2n and a carbon to carbon double bond functional group. Alkynes Hydrocarbons with general formula CnH2n-2 and a carbon to carbon triple bond functional group. Aluminium oxide Catalyst in cracking (not an oxidising agent). Amide link Formed by reaction of an amine group with a carboxyl group. Also called a peptide link. Amino NH2 group present in amines and amides. Amino acids Monomers from which proteins are formed. Contain a Carboxyl group and an amino group. Anaerobic fermentation Animal or vegetable matter decays in the absence of air forming biogas. Aromatics Hydrocarbons containing a benzene ring. Produced from coal or the naphtha fraction of oil. They improve the efficiency of burning in petrol. CA/2/AW6523/Chem-O Benedict’s solution An oxidising agent containing Cu2+, used to oxidise aldehydes to carboxylic acids. Benzene The simplest member of the class of aromatic hydrocarbons, an important feedstock for a range of consumer products eg drugs, dyes. Biogas Mixture of mainly methane (60%) and carbon dioxide, which is a useful fuel in rural areas. Biopol An example of a biodegradable polymer. Bromination Addition reaction between bromine and unsaturated hydrocarbons eg alkenes. Carbonyl CO group present in aldehydes, ketones, esters, carboxylic acids. Carboxyl group COOH group in carboxylic acids. Carboxylic acids Substances containing –COOH (carboxyl) group. Formed by oxidation of primary alcohols via aldehydes, using acidified dichromate. Industrial production of ethanoic acid is by direct oxidation of alkanes from oil or by bacterial oxidation of ethanol from fermentation. Identified by the ‘-oic’ name ending. Catalytic hydration Addition reaction where water adds onto an alkene producing an alcohol. Used industrially to meet the market demand for ethanol. CFC’s Halogenoalkanes which are thought to have been responsible for depleting the ozone layer. Chromatography Separation technique for separating soluble components of a mixture. Condensation polymers Made from monomers with 2 functional groups per molecule eg nylon, a polyamide formed from a diamine and a diacid, by condensation polymerisation. Condensation reaction Organic molecules combine with the removal of water. Consumer products Generally complex molecules which have been synthesised from small reactive molecules, many of which are organic. CA/2/AW6523/Chem-O Covalent radius Half the distance between the nuclei of two of its bonded atoms. Cracking The breaking up of long chain hydrocarbons to produce shorter chain alkanes which are in demand and small unsaturated molecules which are feedstocks for plastics. Cured polyester resins Polyesters with a three dimensional structure. Denatured When the protein structure has been changed by high temperatures on pH changes. Diesel Produced by blending gas oil fractions. Digestion The breakdown of food eg the hydrolysis of proteins to form amino acids. Electrolysis Production of an element from a compound, either molten or in solution, by passing electricity through it eg production of hydrogen from water. Enzymes Biological catalysts. Some are wholly protein, others require a co-enzyme to activate them. Sensitive to pH and temperature. Essential amino acids Amino acids which are not produced in the body so have to be present in dietary protein. Ester link Formed by reaction between a hydroxyl group and a carboxyl group (-COO-) Esters Compounds formed by condensation reaction between an alcohol and a carboxylic acid. Identified by ‘-COO-‘ functional group and ‘-oate’ name ending. Ethene Alkene formed by cracking ethane from natural gas or cracking naphtha from crude oil distillation. Ethyne Common name acetylene. A hydrocarbon containing a triple bond between the 2 carbon atoms C2H2. Fats and oils Mixtures of triglycerides formed by combination of 1 mole glycerol with 3 miles fatty acid. They are examples of esters. They provide energy. Fatty acids Saturated or unsaturated straight chain carboxylic acids with even number of C atoms from C4-C24, primarily C16 and C18. CA/2/AW6523/Chem-O Feedstock Enzyme catalysed process to produce ethanol from carbohydrates. Fibrous proteins Long and thin and form the major structural materials of living tissues. Finite resource A substance which is in limited supply and will run out. Functional group A group of atoms with characteristic chemical reactivity. Globular proteins Spiral chains folded into compact units. Involved in the maintenance and regulation of life processes. Include enzymes, many hormones eg insulin, and haemoglobin. Glycerol Propane- 1, 2, 3-triol, a trihydric alcohol. Haloalkanes See halogenoalkanes Halides Compounds containing a halogen. Halogenoalkanes Halogen substituted alkanes with properties which make them useful in a variety of consumer products (see CFC’s). Hardening A process for partially saturing oils by reacting with hydrogen, using a nickel catalyst, to meet demands for particular properties. Hydrogen economy Possible future use of hydrogen to store and distribute energy. Hydrogenation Addition reaction between alkenes and hydrogen eg in margarine production. Hydrolysate Mixture produced by hydrolysis. Hydrolysis Breaking down in the presence of water eg hydrolysis of fats and oils to fatty acids and glycerol, or proteins to amino acids. Hydroxyl OH group present in alcohols and carboxylic acids. Ketones Group of substances containing –CO group. Produced by oxidation of secondary alcohols with acidified dichromate, resistant to further oxidation. CA/2/AW6523/Chem-O Kevlar An aromatic polyamide which is extremely strong because of the way in which its rigid, linear molecules pack together. It has many important uses. Knocking Caused by auto-ignition of fuel in the engine. Lipases Enzymes which hydrolyse (‘digest’) fats and oils. Liquefied petroleum gas (LPG) Methanal Mixture of mainly propane and butane. Methanol Produced industrially from synthesis gas, used to make methanal. Miscrible Applied to liquids which mix together (dissolve). Naphtha Fraction of crude oil used as a feedstock for alkenes by cracking and for aromatics by reforming. Natural gas Mixture of mainly methane and ethane in varying proportions. Ninhydrin Chemical used to show up the spots in chromatography. Organic Carbon containing compounds. Oxidation Reaction in which electrons are lost. It may happen along with addition of oxygen or removal of hydrogen. Ozone O3 in the atmosphere forms a protective layer which absorbs ultraviolet radiation from the sun. Pepsin Enzyme which hydrolyses proteins to amino acids. Peptide link (=amide link) The link between amino acids (‘-NHCO-‘). Formed by reaction of an amine group with a carboxyl group. Percentage yield (Actual yield/theoretical yield) x 100. Petrol Produced by reforming naphtha. Any petrol is a blend of hydrocarbons of different volatilities which takes account of prevailing temperatures. Phenyl A benzene ring in which one hydrogen has been substituted by another group of atoms – formula ‘C6H5-‘. Alkanal used to produce thermosetting plastics. CA/2/AW6523/Chem-O Photodegradable Can be broken down by light eg low density polythene can be modified during manufacture to produce a photodegradable polymer. Poly(ethanol) A plastic which readily dissolves in water and has many important uses. Made from a plastic by ester exchange. Poly(vinyl carbozole) Polymer exhibiting photoconductivity which is used in photocopiers. Polyamides Examples of condensation polymers formed by reaction of an amine group with a carboxyl group eg nylon. Polyesters Examples of condensation polymers formed by reaction of a hydroxyl group with a carboxyl group. Used as textile fibres and resins. Polymeric esters Used as textile fibres and resins – formed by condensation polymerisation. Primary Functional group as at the end of the chain. Propene Alkene formed by cracking propane from natural gas or cracking the naphtha fraction from oil. Protein Polymer formed by condensation polymerisation of amino acids. Reflux To heat up (at boiling point) using a condenser to prevent loss of vapour. Reforming A set of processes each of which alters the arrangement of atoms in molecules without necessarily changing the size eg conversion of straight chain hydrocarbons and cyclic hydrocarbons in naphtha into branched chains and aromatics, to improve the octane rating of petrol. Renewable source More can be made available eg sugar cane is a renewable source of ethanol for engine fuel. Saturated Containing single C-C bonds. Secondary Functional group is not at a terminal position. Soaps Sodium or potassium salts of fatty acids. Produced by the hydrolysis of fats and oils. CA/2/AW6523/Chem-O Substrate Reactant in an enzyme catalysed reaction. Sugar cane Used as a renewable source of enthanol. Synthesis To bulk up molecules from smaller simpler units. Synthesis gas Mixture of CO/H2/ Obtained by steam reforming of methane from natural gas or steam reforming of coal. Used to make methanol as feedstock for methanal. Tertiary Functional group is at a position where there is a branch on the chain. Triglyceride Ester formed from condensation of 3 moles of fatty acid with 1 mole of glycerol. The fatty acid groups may or may not be identical. Trihydric alcohol An alcohol with 3 OH groups per molecule. Tripeptide Molecule formed from 3 amino acids joined together (not part of a long polymer chain). Unleaded petrol The efficiency of burning is improved using branched chain and/or aromatic hydrocarbons instead of lead compounds. Unsaturated Containing multiple bonds eg C=C alkenes. Volatile Forms a vapour easily. Low B.Pt, but not necessarily flammable. CA/2/AW6523/Chem-O UNIT 3 Artificial sources CHEMICAL REACTIONS Made by bombarding stable nuclei with particles such as neutrons in a nuclear reactor. Batch process A non-continuous manufacturing process. By-product A product of a manufacturing process which is produced alongside the desired product. Carbon dating 14 Compression Increase in pressure. Coulomb Unit of charge. Decay Rearrangement of unstable to stable nuclei with emission of energy. The decay is independent of the physical or chemical state of the element. Dynamic equilibrium Reversible reactions attain a state of dynamic equilibrium when the rates of forward and reverse reactions are equal. Electrolysis Production of an element from a compound, either molten or in solution, by passing electricity through it. One mole of element requires nF coulombs (n=number of electrons in the ion-electron equation, F=the Faraday). Equilibrium When the concentrations of reactants and products remain constant although not necessarily equal. Equimolar Containing the same number of moles. Faraday The charge associated with 1 mole of electrons (96500C). Fission Splitting some nuclei by bombarding them with slowmoving neutrons. Energy is emitted and more neutrons are released leading to a self-sustaining chain reaction. Fusion Forming heavier nuclei by fusing together light nuclei with the emission of large amounts of energy. Elements are created in the stars from simple elements by nuclear fusion. C is used to date archaeological specimens. The ratio of 14C / 12C is know for living things but the 14C decays after death. The ratio for the specimen is measure and the half life for 14C can be used to determine its age. CA/2/AW6523/Chem-O Haber process Industrial process to synthesise ammonia from nitrogen and hydrogen using an iron catalyst. Half-life (t1/2 ) The time taken for the activity of the isotope to decrease by half. It is independent of the mass and is unaffected by temperature, pressure, concentration, catalysts or the physical or chemical state of the isotope. Hess’s Law ∆H is independent of the route taken. Intensity The strength of – eg colour or light. Isotopes Atoms of the same element which differ in the number of neutrons and hence the relative mass. Labelling Molecules can be labelled with radioisotopes to trace the path of chemicals eg 32P in phosphate fertilisers to observe the use of phosphate by growing plants. Le Chatelier’s principle If a system at equilibrium is subjected to any change, the system readjusts itself to try and counteract the applied change. Nuclear fusion See fusion. Mass spectra Output from a mass spectrometer which is used to determine the mass numbers and relative proportions of the various isotopes of an element. Monoprotic acid Containing one hydrogen in the formula eg HCl. Oxidising agent A substance which accepts electrons. pH scale A continuous range from below 0 to above 14 which is related to the H+ concentration (pH = -log[H+]). Pilot study A stage in the manufacture of a new product. A small scale industrial process is examined. Radioactivity A result of unstable nuclei rearranging to become more stable by releasing energy. Radioisotope An unstable nucleus. Used in medicine, in industry, for scientific research including carbon dating and to produce energy by uranium fission and nuclear fusion. Produced in igneous rocks which contain radioisotopes. This is the greatest source of background radiation. Radon CA/2/AW6523/Chem-O Raw materials Naturally occurring substances from which useful materials can be separated or synthesised. The major ones are fossil fuels, metallic ores and minerals, air and water. Redox equations Combination of the ion electron equations involved in the redox reaction. Redox reaction Reactions in which one reactant is oxidised (loses electrons) while the other is reduced (gains electrons). Redox titrations Redox reaction carried out quantitatively where there is a way of indicating the end point eg by a colour change. See volumetric titration. Reducing agent A substance which donates electrons. Relative atomic mass The average value of the relative mass of all atoms of the element. Mass is measured relative to the mass of an atom of 12C. Soaps Salts of weak acids and strong bases (see unit 2). Stoichiometry Relative quantities of substances involved in reactions. Strong acids (or bases) Completely dissociated in solution. Unstable nucleus (=radioisotope) A nucleus in which the proton/neutron ratio is outside the region associated with stable nuclei. Volumetric titration Titration performed to calculate the concentration of a reactant. Weak acids (or bases) Only partially dissociated in solution. particles He nuclei, He2+, they can travel a few cm in air but are absorbed by paper. particles High energy electrons emitted form the nucleus when a neutron changes into a proton and an electron. Can be absorbed by thin aluminium. rays High energy electromagnetic radiation (EMR) emitted either alone or accompanying or particles. Thick lead is required to absorb it. CA/2/AW6523/Chem-O