Debbie IrwinRoss FarrellyPatrick GarnettSydney, Melbourne, Brisbane, Perth andassociated companies around the worldiiPearson Education AustraliaA division of Pearson Australia Group Pty LtdLevel 9, 5 Queens RoadMelbourne 3004 Australiawww.pearsoned.com.au/schools Offces in Sydney, Brisbane and Perth, and associated companies throughout the world.Copyright Pearson Education Australia 2007(a division of Pearson Australia Group Pty Ltd)First published 2007Reproduction and Communication for educational purposesThe Australian Copyright Act 1968 (the Act) allows a maximum of one chapter or 10 per cent of the pages of this work, whichever is the greater, to be reproduced and/or communicated by any educational institution for its educational purposes provided that the educational institution (or the body that administers it) has given remuneration notice(s) to Copyright Agency Limited (CAL) under the Act. For details of the CAL licence for educational institutions contact Copyright Agency Limited (www.copyright.com.au).Reproduction and Communication for other purposesExcept as permitted under the Act (for example a fair dealing for the purposes of study, research, criticism or review) no part of this book may be reproduced, stored in a retrieval system, communicated or transmitted in any form or by any means without prior written permission.All inquiries should be made to the publisher at the address above.Designed by Pearson EducationCover design by Divine Design Cover image by NASAIllustrated by Wendy GortonPrepress work by The Type FactoryProduced by Pearson Education AustraliaPrinted in Hong Kong Cover shows a Hubble image of galaxy NGC 4214National Library of AustraliaCataloguing-in-Publication dataIrwin, Debbie.Chemistry contexts. 1.2nd ed. Includes index.For secondary students.10 ISBN 0 7339 7660 3 13 ISBN 978 0 7339 7660 51. Chemistry.2. Chemistry Problems, exercises, etc. 3. Chemistry Study and teaching.I. Farrelly, Ross.II. Title.540Every effort has been made to trace and acknowledge copyright. However, should any infringement have occurred, the publishers tender their apologies and invite copyright holders to contact them.iiiACKNOWLEDGEMENTSWe would like to thank the following for permission to reproduce photographs, texts and illustrations. The following abbreviations are used in this list: t = top,b = bottom, l = left, r = right, c = centre.Airliquide: p. 307l.Ancient Art & Architecture Collection Ltd, The: p. 102t.Australian Bureau of Meteorology: Ian Forrest, p. 333.Australian Picture Library: pp. 42b, 65b.Bank of Greece: p. 41.Coo-ee Picture Library: pp. 107, 110bl.Farrelly, Ross: p. 324.Fermilab: p. 42t.Heffernan, David: p. 16.Herald & Weekly Times: p. 316b.Jupiterimages Corporation: 2006 Jupiterimages Corporation, pp. 110l, 318Kho, Devin: Photo courtesy by Devin Kho , p. 103br.Mount Isa Mines: pp. 116tl, 116br.Museum Victoria: Source Museum Victoria, photographer Frank Coffa, p. 11.NASA: pp. 7, 103t.Natural History Museum Picture Library: p. 281t.News Limited: Andrew Batsch, p. 316t.Normandy Group: p. 116tr.Parker, Brian: pp. 14, 326br.Pearson Education Australia: Tricia Confoy, pp. 35t, 35b, 72, 102b, 109, 110r, 110br, 128, 195, 221, 279, 307r, 325, 326tl; Kim Gomes, p. 267.Photolibrary: pp. 2, 17b, 18b, 18c, 20, 22, 23, 30, 33, 36t, 36b, 65t, 71, 81l, 81r, 83l, 83c, 83r, 104b, 111, 116bl, 126, 127l, 127r, 129, 142, 143, 144, 145, 194, 198, 203, 222tr, 222b, 239, 263, 270, 281b, 304, 332l, 332r, 336l, 336r.Qantas Airways Limited: p. 106l.Rio Tinto Limited: p. 17t.Simsmetal: p. 120.Spithill, Arthur: p. 4.Sydney Water Corporation: p. 18t.University Museum of Archaeology and Anthropology, Cambridge: p. 102c.Woodside Energy Ltd: Courtesy of Woodside Energy Ltd, p. 283.Every effort has been made to trace and acknowledge copyright. However, should any infringement have occurred, the publishers tender their apologies and invite the copyright owners to contact them.ivivContentsIntroduction viHowtousethisbook viiiOutcomesxTableofrelativeatomicmasses 1MoDULe 1 tHe CHeMICAL eARtH Chapter 1the earth: a mixture of ChemiCals 1.1 The scope of chemistry31.2States and properties of matter: the kinetic theory51.3Classifcation of matter81.4Chemicals of the Earth101.5Useful mixtures 141.6Separation of mixtures151.7Chemical analysis22Key points25Application and investigation27Chapter 2 elements of the earth 2.1Abundance of elements on Earth292.2Formulae of elements312.3Reactivity of elements332.4Metals, non-metals and semi-metals34Key points38Application and investigation39Chapter 3atoms Combine to form Compounds 3.1Atomic theory413.2The arrangement of electrons in atoms463.3Ions473.4Electron dot diagrams503.5Chemical formulae and naming of compounds54Key points59Application and investigation60Chapter 4 ChemiCal Change 4.1Physical and chemical changes644.2Chemical equations674.3Balancing chemical equations694.4Decomposition of compounds704.5Synthesis of chemical substances734.6Bond energy75Key points77Application and investigation78Chapter 5bonding and struCture determine properties 5.1Physical and chemical properties of matter815.2Comparison of properties of compounds and their constituent elements825.3Structure and bonding in substances84Key points92Application and investigation94MoDULe 1 ReVIeW98MoDULe 2 MetALs Chapter 6the extraCtion and uses of metals 6.1The historical use of metals1016.2Contemporary uses of metals 1046.3Alloys1076.4Minerals and ores1116.5The extraction of metals from their ores1156.6 Factors affecting the use of metals1186.7Recycling of metals120Key points123Application and investigation124Chapter 7 ChemiCal reaCtions of metals 7.1Reactions of metals with oxygen1267.2Reactions of metals with water1297.3Reactions of metals with acids1307.4The activity series and ionisation energy1327.5Oxidationreduction reactions1337.6Metals for different purposes136Key points138Application and investigation139Chapter 8 the periodiC table 8.1Development of the periodic table1428.2The modern periodic table1488.3Trends in the periodic table152Key points157Application and investigation158Chapter 9measuring the amounts of substanCes: the mole 9.1Relative atomic mass1629.2Relative molecular and formula mass1659.3Avogadros number and the mole1669.4Moles and numbers of particles1689.5Moles and mass1699.6Percentage composition1719.7Empirical and molecular formulas1729.8Gay-Lussacs law and Avogadros hypothesis1749.9Chemical equations and reacting masses1779.10Limiting reagents and theoretical yields180Key points186Application and investigation187MoDULe 2 ReVIeW191vMoDULe 3 WAteR Chapter 10 Water on earth 10.1The distribution of water on Earth19510.2Solutions19710.3The importance of water in Earth processes19910.4Water density202Key points204Application and investigation204Chapter 11the moleCular struCture of Water and hydrogen bonding 11.1The shapes of simple molecules20711.2Polarity of bonds and molecules20911.3Forces between molecules21511.4Properties of water221Key points225Application and investigation226Chapter 12 Water as a solvent 12.1The solution process22912.2Relating solubility to structure231Key points237Application and investigation238Chapter 13 soluble and insoluble salts 13.1Solubility rules for ionic substances23913.2Reversible reactions and equilibrium systems24313.3Concentrations of solutions24813.4Dilutions25313.5Calculations from chemical equations involving solutions255Key points257Application and investigation258Chapter 14 the heat CapaCity of Water 14.1Specifc heat capacity26114.2Energy changes in chemical reactions26314.3Heat of solution and reaction26514.4Thermal pollution270Key points272Application and investigation273MoDULe 3 ReVIeW275MoDULe 4 eneRGY Chapter 15some Compounds are important sourCes of energy 15.1The production of carbohydrates by plants27915.2Fossil fuels28015.3The origin of fossil fuels281Key points284Application and investigation284Chapter 16the variety of Carbon Compounds 16.1Carbon chemistry28616.2Allotropes of carbon28816.3Bonding in carbon compounds29016.4Representing the structures of carbon compounds295Key points297Application and investigation298Chapter 17 hydroCarbons 17.1Defning hydrocarbons29917.2Naming hydrocarbons30117.3Separation of petroleum (crude oil)30417.4Physical properties of hydrocarbons30817.5Evaporation, vapour pressure and boiling31117.6 The safe handling of hydrocarbons315Key points320Application and investigation321Chapter 18 Combustion of hydroCarbons 18.1Combustion reactions32418.2Energy changes in chemical reactions32718.3Pollution caused by burning fossil fuels329Key points334Application and investigation335Chapter 19 rates of ChemiCal reaCtions 19.1Chemical reactions occur at different rates33619.2Factors affecting the rate of reactions33719.3Collision theory and activation energy34119.4Applying collision theory346Key points354Application and investigation355MoDULe 4 ReVIeW358Index361vviOur aim has been to present Chemistry as an exciting, relevant and accessible discipline. We have structured the books to allow students easy access to information, regular opportunities to review key concepts, and practice at exam-style questions.The coursebook consists of chapters with the following features:engaging colour photos and illustrationsstudent-centred approachchemistry presented through varied contextsto engage and stimulate studentsPrescribed Focus Areas integrated throughoutthe textsKey Points summarychapter review called Application and Investigation with problem-solving questions, investigation activities and skills-based questionsModule Review that develops essential HSCexam skills.ContextsSeConD eDItIonPreliminaryChemistry Contexts second edition is a two-book series that has been specifcally written for the NSW Stage 6 Chemistry course. Book 1 covers the Preliminary course. The material presents Chemistry in context, addressing the majority of the outcomes of the syllabus and preparing studentsfor the HSC examination.CHeMIstRY Contexts 1 seConD eDItIon CoURsebookThe coursebook includes an interactivestudentCD containing: solutions manual link to the live Companion Website.viiCHeMIstRY Contexts 1 seConD eDItIon teACHeRs ResoURCe PACkThe Teachers Resource Pack consists of a CD with printout. All documents are available as: PDFs to make printing easy editable MS Word documents that allow you to modify and adapt any resources to meet your needs.The Teachers Resource Pack provides a wealth of teacher support material including: lab manual fully worked solutions to coursebook questions worksheets and answers teacher demos risk assessments for practical activities teaching program.www.pearsoned.com.au/schools/secondaryThe Companion Website contains a wealth of support material for students and teachers that has been written to enhance teaching and learning: ReviewQuestions: auto-correcting multiple-choice for exam revision WebDestinations: a list of reviewed websites that support further investigation and revision Interactiveanimations to engage students in exploring concepts and reinforcing key ideas QuickTimevideos to explore chemical concepts in a visually stimulating way 3DMoleculeGallery:for viewing and manipulating molecular structures TeachersResourceCentre: password-protected part of the site containing the teachers resources found in the Teachers Resource Pack.QuickTime videoInteractive animationCHeMIstRY Contexts 1 seConD eDItIon CoMPAnIon WebsIteFor more information on the Chemistry Contexts series,visitwww.pearsoned.com.au/schoolsviiiWe have structured the books to allow students easy access to information, regular opportunities to review key concepts, and practice at exam-style questions.To do this, modules are broken down into chapters, which are divided into units that present comprehensive information in manageable-sized portions.The content is written in a very student-friendly style, with larger diagrams for clear explanations. This, along with extensive use of photographs and illustrations, makes Chemistry come alive for students of all abilities. This new edition has added Chemistry Context boxes, which provide students with insights into the history of chemistry, the nature and practice of chemistry, and the applications and uses of science.How to use this bookChemistry Contexts 1secondeditionhasbeenspecifcallywrittenfortheNSWStage6Chemistrycourse.ThematerialpresentsChemistryincontext,addressingthemajorityoftheoutcomesofthesyllabusandpreparingstudentsfortheHSCexamination.ixTo help students consolidate knowledge and to encourage independent learning, each chapter ends with a comprehensive review featuring: Key Points summary Application and Investigation with problem-solving questions, investigation activities, and skills-based questions.Each module ends with a Module Review to provide practice at HSC exam-style questions.THe CHemISTry CoNTexTS 1 SeCoNdedITIoN PaCkageDont forget the other ChemistryContexts 1 second edition componentsthat will help engage students in learningin chemistry: Chemistry Contexts 1 second edition Companion Website Chemistry Contexts 1 secondedition Teachers ResourcePack (CD and printout)CHeMIstRY Contexts 1 seConD eDItIonstUDent CDThe Chemistry Contexts 1 second edition Student CD is a comprehensive resource that will allow students to review their own work and revise key concepts, as well as provide an opportunity for accelerated learning.The Student CD included with this book contains: answers to all questions in the text (except investigation questions). Answers include explanations and fully worked solutions an electronic version of the coursebook link to the live companion website.xChemistry Contexts 1 and stage 6 Chemistry preliminary Course outComesOBJECTIVES PRELIMINARY COURSE OUTCOMESMODULE 1 MODULE 2MODULE 3 MODULE 4PRESCRIBED FOCUS AREAStudents develop knowledge and understanding of:A student:1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 191the history of chemistryP1 outlines the historical development of major principles, concepts and ideas in chemistry 2the nature and practice of chemistryP2 applies the processes that are used to test and validate models, theories and laws of science with particular emphasis on frst-hand investigations in chemistry 3applications and uses of chemistryP3 assesses the impact of particular technological advances on understanding in chemistry 4implications for society and the environmentP4 describes applications of chemistry which affect society or the environment 5current issues, research and developmentsP5 describes the scientifc principles employed in particular areas of research in chemistry DOMAIN: KNOWLEDGE AND UNDERSTANDING6atomic structure and periodic tableP6 explains trends and relationships between elements in terms of atomic structure and bonding 7energy P7 describes chemical changes in terms of energy inputs and outputs 8chemical reactionsP8 describes factors that infuence the type of rate of chemical reactions 9carbon chemistry P9 relates the uses of carbon to the unique nature of carbon chemistry 10stoichiometry P10 applies simple stoichiometric relationships DOMAIN: SKILLS11planning investigationsP11 identifes the need for, drafts and improves investigation plans12conducting investigationsP12 discusses the validity and reliability of data gathered from frst-hand investigations and secondary sources13communicating information and understandingP13 identifes appropriate terminology and reporting styles to communicate information and understanding14developing scientifc thinking and problem-solvingP14 draws valid conclusions from gathered data and information 15working individually and in teamsP15 implements strategies to work effectively as an individual or as a member of a teamNote: the objectives and outcomes above are taken directly from the Stage 6 Chemistry Syllabus pages 16 and 17 Board of Studies NSW 2002.Outcomes addressed through practicals in Chemistry Contexts 1 Laboratory Manual.elementsymbolatomic numberatomic WeightActiniumAc 89 (227.0)AluminiumAl 13 26.98AmericiumAm 95 (243.1)AntinomySb 51 121.8ArgonAr 18 39.95ArsenicAs 33 74.92AstatineAt 85 210.0BariumBa 56 137.3BerkeliumBk 97 (247.1)BerylliumBe 4 9.012BismuthBi 83 209.0Bohrium Bh 107 (264.1)BoronB 5 10.81BromineBr 35 79.90CadmiumCd 48 112.4CaesiumCs 55 132.9CalciumCa 20 40.08CaliforniumCf 98 (251.1)CarbonC 6 12.01CeriumCe 58 140.1ChlorineCl 17 35.45ChromiumCr 24 52.00CobaltCo 27 58.93CopperCu 29 63.55CuriumCm 96 (247.1)Darmstadtium DS 110 (271)Dubnium Db 105 (262.1)DysprosiumDy 66 162.5EinsteiniumEs 99 (252.1)ErbiumEr 68 167.3EuropiumEu 63 152.0FermiumFm 100 (257.1)FluorineF 9 19.00FranciumFr 87 223.0GadoliniumGd 64 157.3GalliumGa 31 69.72GermaniumGe 32 72.64GoldAu 79 197.0HafniumHf 72 178.5Hassium Hs 108 (277)HeliumHe 2 4.003HolmiumHo 67 164.9HydrogenH 1 1.008IndiumIn 49 114.8IodineI 53 126.9IridiumIr 77 192.2IronFe 26 55.85KryptonKr 36 83.80LanthanumLa 57 138.9LawrenciumLr 103 (262.1)LeadPb 82 207.2LithiumLi 3 6.941LutetiumLu 71 175.0MagnesiumMg 12 24.31ManganeseMn 25 54.94element symbolatomic numberatomic WeightMeitnerium Mt 109 (268)MendeleviumMd 101 (258.1)MercuryHg 80 200.6MolybdenumMo 42 95.94NeodymiumNd 60 144.2NeonNe 10 20.18NeptuniumNp 93 237.0NickelNi 28 58.69NiobiumNb 41 92.91NitrogenN 7 14.01NobeliumNo 102 (259.1)OsmiumOs 76 190.2OxygenO 8 16.00PalladiumPd 46 106.4PhosphorusP 15 30.97PlatinumPt 78 195.1PlutoniumPu 94 (244.1)PoloniumPo 84 209.0PotassiumK 19 39.10PraseodymiumPr 59 140.9PromethiumPm 61 144.9ProtactiniumPa 91 231RadiumRa 88 226.0RadonRn 86 (222.0)RheniumRe 75 186.2RhodiumRh 45 102.9Roentgenium Rg 111 (272)RubidiumRb 37 85.47RutheniumRu 44 101.1RutherfordiumRf 104 (261.1)SamariumSm 62 150.4ScandiumSc 21 44.96SeaborgiumSg 106 (266.1)SeleniumSe 34 78.96SiliconSi 14 28.09SilverAg 47 107.9SodiumNa 11 22.99StrontiumSr 38 87.62SulfurS 16 32.07TantalumTa 73 180.9TechnetiumTc 43 97.91TelluriumTe 52 127.6TerbiumTb 65 158.9ThalliumTl 81 204.4ThoriumTh 90 232.0ThuliumTm 69 168.9TinSn 50 118.7TitaniumTi 22 47.87TungstenW 74 183.8UraniumU 92 238.0VanadiumV 23 50.94XenonXe 54 131.3YtterbiumYb 70 173.0YttriumY 39 88.91ZincZn 30 65.41ZirconiumZr 40 91.22(number) indicates Relative atomic mass of most stable isotope if atomic mass not knowntAbLe of ReLAtIVe AtoMIC MAssesChapter 1 The earTh: a mixTureof ChemiCalsChapter 2 elemenTs of The earThChapter 3 aToms Combine Toform CompoundsChapter 4ChemiCal ChangeChapter 5 bonding andsTruCTure deTermine properTiesmodule 1reviewMODULE1This module will cover the following material: thekinetictheoryofmatter originoftheelementsandthechemicalcompositionoftheEarth separationofmixtures theperiodictable Daltonsatomictheory chemicalformulasandequations propertiesofelements atomicstructureandisotopes ionsandionicbonding moleculesandcovalentbonding electrondotformulas chemicaldecompositionandsynthesis metallic,ionic,covalentmolecularandcovalentnetworksubstances extractionofelements.The chemical earthareusedtomanufactureChemicals(suchasacids,bases,salts,organiccompounds,solventsandgases)whichareusedinchemicalindustrytoproducefertilisersPesticidesDrugsandmedicinessoapsanddetergentsExplosivesDyesPaintscosmeticsPlasticmaterialssyntheticfibressyntheticrubberPetroleumproductsinotherindustriestoproduceBuildingmaterialsmetalproductsusedinaircraft,ships,carsandmachineryGlassPaperproductsTextilesPackagingfoodproductsrubberproductsBeveragesraw materials(fromtheair,sea,mines,oilwells,forests)FM 88 92 96 100 108 aM 5.3 6 7 8 10 12 1416 Mhz khz X100OFF ONraDio cassETTE PlaYErfm/am1.1 ThescopeofchemistryChemistry deals with the composition, structure, properties and reactions of matter. Our planet Earth provides us with a vast array of chemical substances to study and use. Metals such as gold and aluminium, non-metals such as carbon, sulfur, oxygen and hydrogen, chemical compounds such as sodium chloride, carbon dioxide, methane and water, and mixtures including crude oil, granite and concrete are used by us every day. The extraction and purifcation of these substances from the Earth can be understood and improved using our increasing knowledge of chemistry.An understanding of chemistry is fundamental to all biological systems including human biology. This relationship exists partly because the biosphere (containing all living things) and the environment in which organisms live are made up of chemical substances. Life itself is a very complicated system of interrelated chemical processes.Chemistry also fnds applications in many other scientifc disciplines. These include agricultural science, engineering, pharmacy, medicine, space science, oceanography and environmental science. The overlap of chemistry with other sciences has led to the development of new sciences that have become disciplines in their own right. Examples of these newer disciplines are biochemistry, geochemistry, astrochemistry Chapter 1ThEEarTh:amixTurEofchEmicalsfigure 1.1 The earth provides the raw materials of the chemical industry. moDulE1:ThechemicalEarthand chemical engineering. Because of its application in many sciences, chemistry is often referred to as the central science.Today, chemists continue to extend our chemical knowledge. Universities, the CSIRO (Commonwealth Scientifc and Industrial Research Organisation), various government instrumentalities and many industries employ chemists to work on a wide range of activities. The extent and importance of chemical industries can be gauged by considering the range of products that are manufactured by these industries. This includes fertilisers, pesticides, food preservatives, petroleum, metals, paper, paint, cosmetics, rubber, plastics, pharmaceuticals, textiles, and many others.Chemistry has made a signifcant contribution to the quality of life in our society. The effciency of the food production industry today is largely due to the use of fertilisers and pesticides. The polymer and plastics industry has had an enormous impact in many areas such as furniture, clothing, childrens toys and food packaging. The pharmaceutical industry, with its development of vaccines, antibiotics and pain relievers, has also had a substantial impact on the quality of life we enjoy.However, side-effects of the chemical industry and the occasional irresponsible use of chemicals have had damaging environmental consequences. The agricultural insecticide DDT has become notorious because it weakens the eggshells of certain birds and has led some species to the verge of extinction. At the beginning of the Second World War, however, DDT was viewed more favourably as it was used extensively in the control of malarial mosquitoes and saved millions of human lives.Another example of the benefcial and detrimental aspects of the application of chemicals is the use of fertilisers. While fertilisers have enabled our agricultural producers to become highly effcient, their indiscriminate overuse, resulting in them being washed into streams and lakes, has contributed to the excessive growth of algae, to the detriment of other aquatic life.These experiences illustrate the need to carefully monitor and control the use of chemicals in all aspects of life. Clearly, the chemical industry makes an important contribution to present-day living standards but it is equally important to ensure that these benefts are not obtained at an unacceptably high cost to the environment.figure 1.2 epoxy fbreglass, Kevlar, mylar, carbon fbre, polyester and stainless steel are just some of the materials used in state-of-the-art yachting. Reviewexercise1.1chaPTEr1:TheEarth:amixtureofchemicals 1.2 Statesandpropertiesofmatter:thekinetictheoryChemistry is the study of the composition, structure, properties and reactions of matter. Matter is defned as anything that has mass and occupies space, such as wood, water, steel and air. Light, sound and magnetic felds are examples of phenomena that are not matter.StatesofmatterMatter commonly exists in three statesgas, liquid and solid. Water, for example, exists as steam, liquid water and ice. The characteristics of solids, liquids and gases are summarised in Table 1.1. These characteristics reveal some information about the arrangement of particles in solids, liquids and gases.Table 1.1 Characteristics of solids, liquids and gases solid liquid gasShape defnite variable variableVolume defnite defnite variableCompressibilityalmostincompressibleveryslightlycompressiblehighlycompressibleDiffusion negligible slow fastThermal expansionslightlyexpandablemoderatelyexpandablehighlyexpandableA model for the arrangement of particles in solids, liquids and gases is illustrated in Figure 1.3.GasesThe kinetic theory uses a model of a gas that assumes gases are made up of particles of matter in a state of constant motion. The term kinetic indicates that it is the motion of these gas particles that plays a key role in their physical properties. The kinetic theory is based on the following assumptions:1Gases consist of tiny particles called molecules.2The average distance between the molecules of a gas is very large compared with the size of each gas molecule, i.e. in gases the particles are widely spaced.3The molecules of a gas move in rapid, random, straight-line motion.These movements result in collisions with each other and with the sidesof any container.1Identify one chemical used for each of the following: food preservative, analgesic (pain killer), cleaning agent, fuel, fertiliser, pesticide, building material, antibiotic, textile, plastic.2Defne each of the following felds of science: biochemistry, geochemistry, astrochemistry and chemical engineering.GasParticlesfarapartandmoveindependentlyofoneanother.LiquidParticlesclosetooneanotherbutfreetomove.SolidParticlescloselypackedandheldinposition. moDulE1:ThechemicalEarth4The molecules of a gas exert negligible attractive or repulsive forces on one another, so the molecules move virtually independently.5All collisions of gas molecules are perfectly elastic. This means that there is no net energy loss during these collisions.6The average kinetic energy of the molecules increases as the temperature of the gas increases.The kinetic theory is used to explain the physical properties of gases. Gas pressure is explained in terms of collisions of the gas molecules with the walls of the container. For example, an infated balloon maintains its shape due to collisions of the gas molecules with the inside surface of the balloon.The diffusion of gases can be explained in terms of the constant motion of gas molecules. If a bottle of perfume is spilt, the scent quickly becomes apparent throughout the room. This is because gas particles are in constant motion and will continue to move in all directions until stopped by the walls of a container. Gases always spread to occupy all the available space. This is called diffusion.The compressibility of gases can be explained by the large spacing between the molecules compared with the size of each molecule. Most of the volume occupied by a gas is empty space. As a result, gases can be compressed, as happens in car and bicycle tyres and in gas cylinders. The kinetic theory can be extended to explain the behaviour of solids and liquids. In the gaseous state, the particles are widely spaced and exhibit random straight-line movement. Intermolecular forces are so small that they can be ignored. However, in solids and liquids (the condensed states) the particles are much closer together and are restricted in their movement. Attractive forces exist between the particles. As a result, the properties of solids and liquids are quite different from those of gases.LiquidsAlthough the particles are much closer in liquids than in gases, they still constantly change their positions. The particles can slip past each other but, because of their close proximity, a particle cannot travel far before colliding with a figure 1.4 gases spread to occupy the available space. The spacing between molecules is very large compared with the size of the molecules.figure 1.3 arrangement of particles in solids, liquids and gases Reviewexercise1.2GascylinderlargeseparationbetweenparticlesParticlesinrapidrandommotioncollisionsareperfectlyelasticchaPTEr1:TheEarth:amixtureofchemicals figure 1.6 There is a fourth state of matter, plasma, which makes up most of the matter in the universe. This is composed of rapidly moving charged particles such as electrons and positive ions and is found in stars.neighbouring particle. This allows the particles to move relative to one another and is why liquids have a variable shape. The fact that the particles of a liquid do not occupy fxed positions allows the liquid to fow and hence take on the shape of its container. It is also the reason that diffusion occurs in liquids. The lack of space between particles is the reason that liquids are virtually incompressible and have a defnite volume. SolidsIn solids the particles are closely packed and held fairly rigidly in position. The movement of particles in solids is therefore more restricted than in liquids, and much more restricted than in gases. Each particle in a solid occupies a fxed position in relation to its neighbours and the particles vibrate about these fxed positions in the limited space available to them. As a result, solids have a defnite shape as well as a defnite volume.figure 1.5 The kinetic theory accounts for the behaviour of gases.1Outline how the models of gases, liquids and solids presented in Figure 1.3 can account for each of the observed characteristics of these states of matter given in Table 1.1.2Explain how a smell produced from cooking in the kitchen can quickly travel around a whole house.3Analyse how the kinetic theory explains the fact that the pressure of a gas in a sealed container remains constant indefnitely, provided the volume and temperature are kept constant.4Account for the observation that gases are easily compressed.5Explain why gases spread to occupy the available space.6Use the kinetic theory to describe the different arrangement of particles in solids and liquids, and explain the properties that result.Matter(hasmassandoccupiesspace)pure substances(constantcomposition)Mixtures(variablecomposition)elements(notseparableintosimplersubstances)Compounds(twoormoreelementschemicallycombinedinfixedproportions)Solutionshomogeneous mixtures(uniformcompositionandpropertiesthroughout)Solutionsheterogeneousmixtures(variablecompositionandpropertiesthroughout) moDulE1:ThechemicalEarth1.3 ClassifcationofmatterThe matter that makes up the Earth includes naturally occurring matter such as rocks, air and water, and matter modifed by human activity such as most metals, glass and plastics. A classifcation scheme for different kinds of matter found on Earth is shown in Figure 1.7. In this scheme, matter is classifed into pure substances and mixtures.Pure substances consist of matter that is homogeneousthat is, it has the same type and distribution of particles throughout, and a defnite, fxed composition. Pure substances include elements and compounds. Elements are substances that cannot be separated by chemical change into simpler substances, such as carbon, oxygen and copper. They also consist of only one type of atom. Compounds are substances composed of two or more elements combined in fxed proportions. Water and carbon dioxide are examples of compounds. Water consists of hydrogen and oxygen, which are chemically combined; carbon dioxide contains combined carbon and oxygen. Compounds have quite different properties from those of the elements they contain. Water, for example, has very different properties from the elements hydrogen and oxygen which, as elements, exist as gases at normal temperatures. Iron(II) sulfde is a compound that contains chemically combined iron and sulfur. Like most compounds, iron(II) sulfde has vastly different properties from those of the elements from which it is formed (see Table 1.2).Table 1.2 properties of iron, sulfur and iron(ii) sulfde iron sulfur iron(ii) sulfdeState at 25C solid solid solidColour grey yellow blackMelting point (C) 13 113 119Boiling point (C) 20decomposesDensity (g/cm3).9 2.1 .Magnetic yes no nofigure 1.7 Classifcation of matterElementsCompoundsMixtures(a) (b)(d) (e)(f) (g)(c)X2XYZ Y2XZ2X2 and Z Y2 and XZ2chaPTEr1:TheEarth:amixtureofchemicals 9Matter that contains two or more pure substances is described as a mixture. Mixtures can contain different proportions of the same component substances. Pure substances, on the other hand, always have the same composition.Mixtures can be homogeneous or heterogeneous. Homogeneous mixtures have uniform composition and properties throughout. For example, when sugar is dissolved in water, it forms a solution in which the sugar and water are uniformly mixed, and is therefore homogeneous. A container of air is another homogeneous mixture, this time of gases.Heterogeneous mixtures are those that are not uniform in composition and properties throughout. For example, granite is a heterogeneous mixture that consists of the minerals quartz, feldspar, mica and usually hornblende. It is often possible to identify these separate components in a granite sample by visual observation. Concrete, which consists of cement, sand and rock aggregate, is another example of a heterogeneous mixture.In Figure 1.8, atoms are represented as shaded circles. Figures a, b and c are representations of three different elements, X, Y and Z. As they illustrate elements, each contains only one type of atom. Note that in a and b the atoms are combined into pairs (diatomic molecules) and the element is represented as X2 and Y2. In c the atoms exist separately (as monatomic molecules) and the element is represented as Z. Compounds are combinations of different elements, as illustrated in d and e. In d one atom of Y is combined with one atom of X and is represented as XY. In e two atoms of Z are combined with each atom of X and the compound is represented as XZ2.Mixtures are not pure substances. For example, f illustrates a mixture of elements X2 and Z, while g represents a mixture of element Y2 and compound XZ2.figure 1.8 The classifcation of matter using three imaginary elements, x, Y and Z Reviewexercise1.3(i) (ii) (iii)(iv) (v) (vi)10 moDulE1:ThechemicalEarth1Distinguish between the following terms:aelement and compoundbhomogeneous mixture and heterogeneous mixtureccompound and homogeneous mixture.2If represents an atom of P and an atom of Q, identify for each of the diagrams below:awhether an element, compound or mixture is presentbthe symbolic representations of the substances present.3Classify the following as elements, compounds,homogeneous mixtures or heterogeneous mixtures:amolten ironbsaltccarbon dioxidedsugarelemonadefnitrogengwaterhconcreteiairjwine.1.4 ChemicalsoftheEarthAbout 4.5 billion years ago, large amounts of material from exploded stars came together under the infuence of gravity to form the sun and planets in our solar system. Initially the Earth may have been a cold, relatively homogeneous body. Some time in the frst billion years, the Earths temperature rose signifcantly. This was probably a result of the release of heat due to gravitational contraction, the impact of meteors on the Earths surface and the radioactive decay of some elements. The increase in temperature caused the Earth to melt and allowed some separation of the substances making up the Earth. This process is known as differentiation or fractionation. The more dense elements such as iron and nickel sank to form a core, while in the outer regions, oxygen combined with other elements to form a variety of compounds.AlayeredstructureToday the Earth is believed to have a layered structure (see Figure 1.9) consisting of:1a dense core of mostly iron and nickel2a thick, relatively homogeneous mantle composed mainly of magnesium and silicon oxides, and magnesium and iron silicates3a thin, heterogeneous crust, consisting of oxygen, silicon, aluminium, iron, calcium, sodium, potassium, magnesium and less than 1% of the many other elements.atmosphere(1100km)hydrosphere(discontinuous)lithosphere00kmmantle02900kmliquidcore290090kmsolidcore9030kmatmosphere(1100km)lithosphere00kmhydrosphere(discontinuous)chaPTEr1:TheEarth:amixtureofchemicals 11Evidence for this layered structure comes from observations of the Earths density and seismology (the study of how shock waves, generated by earthquakes, travel through the Earth).The Earths crust includes a solid lithosphere, liquid hydrosphere and gaseous atmosphere, together with a living biosphere that overlaps the other three components. These are the parts of the Earth with which we interact the most and therefore of which our chemical knowledge is greatest. Their composition includes combinations of many elements, compounds and mixtures.ThelithosphereThe lithosphere is composed mostly of rocks and soil, which are mixtures of minerals. Minerals are naturally occurring solid elements or compounds with a defnite composition or range of compositions. Examples of minerals include: quartz, a compound of silicon and oxygen; feldspars, which are a group of compounds containing various combinations of sodium, potassium, calcium, aluminium, silicon and oxygen; calcite, containing calcium, carbon and oxygen; and many other minerals such as pyroxene, biotite, iron oxides and kaolinite, a clay mineral. Few elements are found uncombined in the lithosphere, with gold, sulfur and carbon being notable exceptions.TheatmosphereThe atmosphere is a mixture composed mostly of uncombined lighter elements such as nitrogen, oxygen and argon with small percentages of compounds such as carbon dioxide, methane and water. The composition of the atmosphere is shown in Table 1.3 but varies somewhat according to location and climate.figure 1.9 layered structure of the earthfigure 1.10 Quartz (silicon dioxide) can sometimes be found as well-developed six-sided crystals.figure 1.11 Carbon and other elements are continuously being recycled throughout the various components of the environment.shellslimestoneDeath anddecayHydrosphereBiospherefossilfuelsRespirationAtmospherecarbon dioxideDecompositionPhotosynthesisfeedingCO2dissolved in waterCombustion12 moDulE1:ThechemicalEarthTable 1.3 Composition (by volume) of unpolluted dry* air substance percentageNitrogen .1oxygen 20.9argon 0.93carbondioxide 0.03others Each