Worksheet Chapter 14: Chemistry in industry and technology glossary

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1 Worksheet 14.1 Chapter 14: Chemistry in industry and technology glossary Active site The region of an enzyme or catalyst that binds the substrate or reactant molecule(s) and catalyzes a reaction. Addition polymerization A type of polymerization which occurs when alkene-based monomers undergo repeated addition reactions to form a single molecule. Adsorption The accumulation, usually temporarily, of gases, liquids or solutes on the surface of a solid or liquid through the formation of weak intermolecular interactions. Allotropy The ability of an element to exist in different crystalline forms or allotropes. Carbon exists in three allotropic forms: diamond, graphite and fullerene. Alloy An alloy is a homogeneous mixture of metals or metals with a non-metal. Amalgam A solid or liquid alloy which contains mercury. Amphoteric A substance capable of accepting or donating protons, it is able to behave as an acid and a base. Annealing A method of heat treatment in which the metal is allowed to cool slowly to produce a soft malleable steel. Anode The anode is where oxidation (the loss of electrons) occurs during an electrochemical process. In an electrolytic cell the anode is the positive electrode. In an electrochemical cell it is the negative electrode as the oxidation half-reaction produces electrons which can move in the external circuit. Anodizing A process for protecting aluminium. A thin aluminium oxide layer is formed when sulfuric acid is electrolysed with the aluminium object as the anode. Atactic A polymer chain in which the substituents, or side chains, are randomly distributed along the chain. Propene and PVC, for example, have atactic forms. Basic oxygen converter In the basic oxygen process scrap steel and a small amount of limestone are dissolved in molten iron. Pure oxygen is then blown into the molten mixture to remove impurities. Batch process A process which produces a specified amount of a product in a single operation. Battery A collection of galvanic or electrochemical cells connected in series or in parallel. Biphenyl nitriles A series of organic molecules with an alkyl group bonded to two benzene rings and a nitrile functional group. They have liquid crystal properties. 1

2 Blast furnace A furnace in which iron oxide is reduced to iron by using a strong blast of air to produce carbon monoxide from coke, and then using this gas as the reducing agent. Bleach A substance used to decolourise materials by a process of oxidation or reduction. Sodium chlorate (I) is an example. Brine A concentrated aqueous solution of sodium chloride. It is electrolysed to make sodium hydroxide, chlorine and hydrogen, T and sodium chlorate (I). By-products Unwanted products of a chemical synthesis or manufacturing process. Carbocation A carbocation is an organic ion with a positive charge on an electron-deficient carbon atom. They are intermediates in many heterolytic reaction mechanisms. Carbon nanotubes These are made from cylinders of carbon hexagons with carbon pentagons at the ends to close the structure. They have novel properties, which make them useful in many applications in nanotechnology, electronics, optics and other fields of materials science. Cast iron The solidified iron produced in the blast furnace. It is brittle, but very hard. Catalysis A reaction process accelerated by the presence of a substance (a catalyst) which is neither consumed nor produced during the overall reaction. Catalyst A substance which, when present in relatively small amounts, increases the rate of a chemical reaction, but which is not consumed during the overall process. A catalyst provides a new reaction pathway with lower activation energy. Catalytic cracking Cracking carried out in the presence of a heated catalyst, for example, aluminium oxide (alumina) or silicon dioxide (silica). Cathode The cathode is where reduction (the gain of electrons) occurs during an electrochemical process. In an electrolytic cell the cathode is the negative electrode. In an electrochemical cell the cathode consumes electrons in a reduction half-reaction, making it the positive terminal of the cell. Cell potential The potential difference between the two electrodes (in their standard states) of an electrochemical cell. Chain reaction A chain reaction occurs when a reaction intermediate generated in one step reacts in such a way that it is regenerated. Chemical feedstock The raw materials required for an industrial process. Chlor alkali industry The chlor alkali industry is based on the electrolysis of brine. Sodium hydroxide, chlorine and hydrogen are products. Coal A brown or black deposit composed largely of carbon. It is a fossil fuel formed by the action of heat and pressure on the remains of plants buried under sediments. 2

3 Coke This is produced when the volatile components in coal have been removed by heating. It contains a very high percentage of carbon. Condensation polymerization A type of polymerization which involves the elimination of small molecules, usually water. Contact process An industrial process for the manufacture of sulfuric acid. Sulfur dioxide and air are passed over a heated vanadium (V) oxide catalyst to produce sulfur trioxide which is dissolved in sulfuric acid to form disulfuric acid (H 2 SO 4 (l) + SO 3 (g) H 2 S 2 O 7 (l) H 2 S 2 O 7 (l); H 2 S 2 O 7 (l) + H 2 O (l) 2H 2 SO4 (l)) which is further diluted to make sulfuric acid. Copolymer A polymer formed from two or more different monomers. Corrosion The process by which a metal undergoes oxidation by air and water. Cracking The process of breaking down long chain alkanes into smaller alkanes and alkenes using heat, usually in the presence of a catalyst. Cross linking The presence of covalent bonds between adjacent chains in a polymer. This strengthens the material. Crude oil or petroleum A mixture of hydrocarbons formed originally from marine animals, trapped between layers of sedimentary rock. It is obtained by drilling. Cryolite Sodium hexafluoroaluminate (Na 3 AlF 6 ) is a mineral used in the electrolysis of aluminium oxide. It reduces the melting point of the oxide and so reduces the energy costs of the process. Current The rate of flow of electric charge through a conductor. The charge can be carried by electrons in metals, or ions in an aqueous or molten ionic compound. It is measured in coulombs per second or Amperes. Detergent Water-soluble mixtures that can emulsify grease and remove dirt. Diaphragm cell An industrial electrolytic cell used to electrolyze aqueous sodium chloride solution. A porous diaphragm is used to separate the electrodes and prevent the products from reacting. Doping The addition of impurities to the crystal lattice of silicon so as to increase its conductivity. The addition of Group 3 elements produces p-type conductors and the addition of Group 5 elements produces n-type conductors. Ductility The ability of metals to be drawn out under tension and stretched into wires. Electrode A conductor which dips into the electrolyte of an electrolytic or voltaic cell and allows the current to flow to and from the electrodes. An electrode which is involved in the cell reactions is called an active electrode. Inert electrodes are not involved in the cell reaction. Electrolysis A process in which chemical decomposition of a substance, known as the electrolyte, is caused by an electric current. 3

4 Electrolyte An electrolyte is an ionic compound, a salt, alkali or acid, which conducts electricity when it is melted or dissolved in water. An electrolyte does not conduct electricity when solid. Ester Organic compounds formed by the condensation reaction between alcohols and acids. Esters formed from carboxylic acids have the general formula RCOOR. Esterification The reaction between an acid and alcohol to form an ester and water. Expansion moulding A process used in the manufacture of expanded polystyrene. A volatile hydrocarbon, such as pentane, is placed into a mould and heated when styrene (phenylethene) polymerizes. The product has a low density, is white, opaque and an excellent thermal insulator. Feedstock The raw material(s) for an industrial chemical process. Fossil fuel Non-renewable fuels, such as coal, oil and natural gas, formed underground over geological periods of time from the decaying remains of plants and animals. Fraction A mixture of liquids with similar boiling points collected by fractional distillation. Fractional distillation Distillation used to separate volatile liquids with different boiling points. The products are collected in a series of separate fractions, each with a higher boiling point than the previous fraction. Free radical A species with one or more unpaired electrons, often produced by photolysis. They act as highly reactive intermediates in hemolytic reaction mechanisms. Fuel cell A device which converts chemical energy directly into electrical energy. A gaseous fuel, usually hydrogen or a hydrocarbon, and oxygen are passed over porous electrodes where combustion occurs. This is accompanied by the production of an electric current. Fuels Chemicals that burn in air or oxygen and release heat energy. Fullerenes A group of cage-like hollow molecules composed of hexagonal and pentagonal groups of an even number of carbon atoms. Haber Process The industrial manufacture of ammonia from nitrogen and hydrogen, carried out at high pressure (200 atm.) and moderate temperature (450 C) in the presence of an iron catalyst. Haematite This is a mineral form of iron(iii) oxide (Fe 2 O 3 ), used as a raw material in the blast furnace. Half-cell An electrode in contact with a solution of ions. Half-reactions The two parts of a redox reaction, one describes oxidation and the other reduction. Heterogeneous catalyst Heterogeneous catalysis occurs when the catalyst and the reactants are in different phases (or states). 4

5 Heterolytic fission The breaking of a covalent bond, where one of the atoms or groups takes both bonding electrons and becomes negatively charged. The other atom or group is left with a positive charge. High Density Polyethene HDP is produced at low pressure and temperature in the presence of Zeigler catalysts (Al (C 2 H 5 ) 3 & TiCl 4 ). It has very little branching and forms a regular lattice. It has higher density and higher melting point than LDP. Homogenous catalysis Occurs when the catalyst and the reactants are in the same phase (or states). Homolytic fission The breaking of a covalent bond with one electron from the bond left on each fragment. It results in the formation of two free radicals. Hydrocracking A process by which the hydrocarbon molecules of crude oil or petroleum are broken into simpler molecules, by the addition of hydrogen under high pressure and in the presence of a catalyst. Hydrocarbons Organic compounds containing hydrogen and carbon atoms only. Initiation The first elementary step in a free radical reaction. It involves the homolytic fission of a bond, typically by ultraviolet radiation or high temperature, to produce free radicals. Intermediate A chemical species that is neither a reactant nor a product but is formed and consumed during the overall chemical reaction. Intermediates never appear in a rate expression. Isocyanate Isocyanate is the functional group of atoms N = C = O. Polyurethanes are produced by monomers with two isocyanate groups combining with monomers with two hydroxyl groups. Isocyanate Isotactic A polymer chain in which the substituents, or side chains, are distributed on the same side of the chain. Propene and PVC, for example, have isotactic forms. Knocking A knocking noise made by a petrol engine in car, as a result of premature combustion. Lead acid battery The battery used in cars with a lead anode, a lead (IV) oxide cathode and a sulfuric acid electrolyte. 5

6 Lean-burn engine Lean combustion engines are designed to increase fuel efficiency without reducing power. All engines burn a mixture of air and fuel, but a lean-burn engine has a higher air-tofuel ratio than conventional engines. Its use can lead to significant savings in petrol and reduction in carbon dioxide emissions. Liquid crystals These are fluids with physical properties (electrical, optical and elasticity) dependent on molecular orientation relative to some fixed axis in the material. Low Density Polyethene LDP is produced at high temperature and very high pressure in the presence of a free-radical initiator (small amounts of O 2 or peroxides). It is a branched chain polymer with an irregular lattice. It has a lower density and lower melting point than HDP. Lyotropic liquid crystals These are solutions which show the liquid-crystal state at a certain concentration range. Malleability The ability of metals to be bent and beaten into thin sheets. Mercury cathode cell An industrial electrolytic cell used to electrolyze aqueous sodium chloride solution. The sodium formed at a flowing mercury cathode reacts with water to produced hydrogen. Metal Chemical elements which are shiny solids and are good conductors of heat and electricity when solid. They form positive ions (cations). They are located on the left-hand side of the Periodic Table and possess one, two or three electrons in the outer shell which take part in chemical bonding. Metallic bonding Metallic bonding, found in metals and mixtures of metals (known as alloys), consists of a lattice of cations surrounded by delocalized or mobile valence electrons. Metalloid Elements which show some of the physical properties of metals, but the chemical properties of non-metals. Mineral A naturally occurring element or compound which is used as a raw material in the chemical industry. Monomer A small molecule which can be polymerized to form a polymer. Nanotechnology Research development at nm range, which uses structures which, because of their small size, have novel properties. It builds on the ability to manipulate material at the atomic scale. Physical techniques allow atoms to be manipulated and positioned to specific requirements and chemical technique positions atoms in molecules using chemical reactions. Naphtha A light hydrocarbon fraction produced from the fractional distillation of crude oil with a boiling point between 40 C and 150 C. It is an important feedstock used to manufacture other substances. Natural gas Gas obtained from underground deposits and often found with crude oil or petroleum. It contains a high proportion of methane. 6

7 Nematic liquid crystals These are made from rod-shaped molecules and are used in the liquidcrystal displays. Their ability to transmit light depends on the relative orientation of the molecules to the plane of polarization. This orientation can be controlled by applying a small electric field. Nitrile A compound with the C N functional group. They can be hydrolyzed to carboxylic acids. n-type semiconductor An n-type semiconductor is formed when small amounts of Group 5 elements are added to silicon. They donate extra electrons into unoccupied energy level in the silicon atoms and increase the conductivity. Nylon A condensation polymer with a long chain of carbon atoms with amide groups ( NH CO ) at regular intervals. There is extensive hydrogen bonding between the chains. Octane number A measure of the antiknock properties of motor fuel, compared to a standard reference fuel, iso-octane (2,2,4-trimethylpentane), which has an octane number of 100. Ore A naturally occurring mineral from which a metal can be extracted. Organic peroxides These are organic compounds which contain an O O single bond (ROOR'). This bond is readily broken to give two free radicals: ROOR' RO + OR'. Oxidation Oxidation involves an increase in oxidation number or loss of electrons. Oxidation number A number, positive or negative, given to indicate whether an element has been reduced or oxidized during a redox reaction. Oxidizing agent A chemical or substance that brings about oxidation; it accepts electrons from the reactant or one of the reactants. In the reaction the oxidizing agent is itself reduced. Phase A physically or chemically distinct part of a chemical equilibrium. A phase is homogenous throughout and is separated from other phases by a phase boundary. Pixel In digital imaging this is the smallest unit of a picture that can be controlled. Plane-polarized light Electromagnetic radiation in which the electric and magnetic components of the wave oscillate in a single plane. It is used to detect optical activity. Plastic Materials that can be shaped by applying heat or pressure. Plasticizer A substance added to a synthetic (man-made) plastic to make it flexible. Plasticizers are used, for example, to make PVC more flexible. Polar covalent bond A bond formed where the pair of bond electrons are shared unequally between two atoms due to a difference in electronegativity. The more electronegative atom has a partial negative charge the other atom has an equal, but opposite, partial negative charge. Polyamide A polymer in which the monomer molecules are linked by amide bonds. Nylon and Kevlar are examples. Polyamide 7

8 Polyester A synthetic polymer formed by reacting alcohols with carboxylic acids, so that the monomers are linked ester functional group, PET is an example. Polyester Polymer A compound containing very large molecules composed of repeating units called monomers. Polymerization A chemical reaction in which many small molecules called monomers are joined together covalently to form a polymer. Polyurethane Polyurethanes are addition polymers there are no small molecules formed as byproducts during the polymerization reaction. The presence of the hydrogen atoms bonded to the nitrogen atoms along the chain allows hydrogen bonds to form between the polymer chains. Potential difference (voltage) The potential difference between two points is a measure of the energy given out as 1 C charge passes between the two points. If the potential difference between two points is 1 volt, then the passage of 1 coulomb of charge between these points involves 1 joule of energy. It is a measure of the force pushing electrons around a circuit. Power (of a galvanic cell) The power of a cell (measured in watts (W)) is given by the product of the voltage and the current. Primary cell A cell produces a flow of electric current. A primary cell cannot be recharged. Propagation An elementary reaction step in a free racical mechanism. It involves one free radical causing the formation of another radical. p-type semiconductor Formed when the substances such as Group 3 elements are added to silicon and take electrons from its occupied energy level to leave positive holes. These move in the opposite direction to the electrons which move in the lattice to fill them and increase the conductivity of the semiconductor. Quenching A method of heat treatment in which a very hot metal is rapidly cooled so that the hightemperature crystal structure is retained, giving a hard, brittle steel. Radical initiators These are substances that produce radical species under mild conditions and promote free radical reactions. They generally possess weak bonds. Redox equation An equation constructed by combining two half-equations so the numbers of electrons on both sides of the equation cancel. Redox reaction A reaction involving the transfer of electrons. They form the basis of electrochemical cells. Reduction Reduction involves a decrease in oxidation number or gain of electrons. Reducing agent A chemical or substance that brings about reduction; it gives electrons to the reactant or one of the reactants. In the reaction the reducing agent itself is oxidized. 8

9 Refining The processes which separate, convert and purify chemicals in crude oil or the removal of impurities from metals. Repeating unit The unit of a polymer chain that originates from a single monomer, in the case of addition polymers, or from the pairing of two molecules in a condensation polymer. Rusting The corrosion of iron or steel due to the presence of oxygen and water. Secondary cell A secondary cell can be recharged by an electric current. It is based on a reversible redox reaction. Semiconductor A crystalline material with a conductivity intermediate between that of a conductor and an insulator. Its conductivity rises with increasing temperature. This should be contrasted with that of metals, which decrease with temperature. Slag A mixture of molten non-metallic oxides produced during the extraction of iron in the blast furnace or steel in the BOC. It consists of oxide impurities that have reacted with the calcium oxide produced from the thermal decomposition of limestone. Soap A sodium or potassium salt of a long-chain organic acid used to clean in aqueous solution. Steam cracking Cracking in the presence of steam at very high temperatures. Steam reforming The reaction of naphtha with steam over a platinum/alumina catalyst to give a variety of branched-chain alkanes, cycloalkanes and aromatic compounds, used in the blending of fuels. Storage cell An electrochemical cell that stores useful quantities of electrical energy, in the form of chemical energy. Rechargeable batteries, such as the lead-acid battery, are examples. Tempering A method of heat treatment in which the quenched steel is reheated to achieve a hardness intermediate between that achieved by annealing and quenching. Termination An elementary step in a free-radical reaction which involves two radicals combing together. Thermal cracking Cracking carried out a high temperature in the absence of a catalyst. Thermal decomposition The decomposition of a substance by heating. Cracking and the conversion of calcium carbonate in a blast furnace are examples. Thermoplastics Plastics which soften when heated and can then be re-moulded. Most addition polymers are thermoplastics. Thermosetting plastics Plastics which do not soften on heating but only char and decompose they cannot be re-moulded. Bakelite is an example. Thermotropic liquid crystals These are pure substances which show liquid-crystal behaviour in a temperature range between the solid and liquid states. 9

10 Voltaic cell Voltaic or galvanic cells contain two half-cells, each of which is composed of an electrode in contact with an electrolyte. They are sometimes connected with a salt bridge and an external circuit. Zeolite A naturally occurring series of aluminosilicate rocks that contain cations in the cavities of the aluminosilicate framework. They are widely used as catalysts and in ion-exchange columns. Ziegler Natta catalyst A catalyst of titanium (IV) chloride and triethylaluminium. 10