Collins Concise Revision Course: CSEC® Chemistry PDF

~ Collins CONCISE REVISION COURSE ® emlst ,- Anne lindale Collins CONCISE REVISION COURSE ® emlsf " Anne lindale Collins HarperColiins Publishers Ltd The News Building I London Bridge Stree...

~ Collins CONCISE REVISION COURSE ® emlst ,- Anne lindale Collins CONCISE REVISION COURSE ® emlsf " Anne lindale Collins HarperColiins Publishers Ltd The News Building I London Bridge Street London SE I 9GF First edition 2016 1098765432 © HarperColiins Publishers limited 2016 ISBN 978-0-00-815788-3 Collins® is a registered trademark of HarperCollins Publishers limited Concise Revision Course: CSEC® Chemistry is an independent publication and has not been authorised, sponsored or otherwise approved by CXC®, CSEC®is a registered trade mark of the Caribbean Examinations Council (CXC). www.collins.co.uklcaribbeanschools A catalogue record for this book is available from the British Library. Typeset by QBS Printed in Italy by Grafica Veneta S.p.A. All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission in writing of the Publisher. This book is sold subject to the conditions that it shall not, by way of trade or otherwise, be lent, re-sold, hired out or otherwise circulated without the Publisher's prior consent in any form of binding or cover other than that in which it is published and without a similar condition including this condition being imposed on the subsequent purchaser. If any copyright holders have been omitted. please contact the Publisher who will make the necessary arrangements at the first opportunity. Author:Anne Tindale Publisher: Elaine Higgleton Commissioning Editor: Peter Dennis Managing Editor: Sarah Thomas Copy Editor: Delphine Phin Editor:Aidan Gill Proofreader:Tim Jackson Artwork: QBS Cover: Kevin Robbins and Gordon MacGilp Acknowledgements The publishers would like to thank the following for permission to use their photos in this book: p72:Anne Tindale; p89:Anne Tindale; pi 03:Andre Nitsievsky/Shutterstock; p 134: Photo smileJShutterstock; p I461:Toa55/Shutterstock; p 146r: Lodimup/Shutterstock; p 1671: PChStudiosJShutterstock; p 167r: Mark Sykes/Science Photo library; p 178: Mikadun/Shutterstock; p I 841:ThamKC/Shutterstock; p 184r: Mexrix/Shutterstock; p 186:Anne Tindale; p 187:Anne Tindale Contents The pathway to success v Reversible reactions 50 Revision questions 50 1 The states of matter 1 The particulate theory of matter 1 8 The mole concept 51 Evidence to support the particulate Relative atomic, molecular and formula masses 51 theory of matter The mole 52 Uses of osmosis 3 The mole and mass 52 Types of particles that make up matter 3 The mole and number of particles 53 The three states of matter 4 The mole, mass and number of particles 54 Changing state 4 The mole and volumes of gases 55 Revision questions 6 The mole, mass, number of particles and gas volume 55 2 Pure substances, mixtures and Revision questions 56 separations 7 The mole and chemical formulae 56 Pure substances 7 Percentage composition 58 Mixtures 9 The mole and solutions 58 Solutions, suspensions and colloids 9 Revision questions 59 Solubility 11 The mole and chemical reactions 60 Separating the components of mixtures 12 Revision quest-ions 63 The extraction of sucrose from sugar cane 16 9 Acids, baS1?S and salts 64 Revision questions 17 Acids 64 3 Atomic structure 18 Bases 67 Subatomic particles 18 Distinguishing between acids and alkalis 68 The arrangement of subatomic particles The strength of acids and alkalis 68 in an atom 19 Amphoteric oxides and hydroxides 69 Isotopes 20 Classification of oxides 70 Revision questions 23 Revision questions 70 Salts 71 4 The periodic table and periodicity 24 Methods used to prepare salts 72 The historical development of Salts in everyday life 76 the periodic table 24 Neutralisation reactions 77 The modern periodic table 24 Volumetric analysis 78 Trends in Group 11- the alkaline earth metals 26 Revision questions 81 Trends in Group VII - the halogens 27 10 Oxidation-reduction reactions 82 Trends in Period 3 28 Revision questions 29 Oxidation-reduction reactions in terms of electrons 82 5 Structure and bonding 30 Oxidation number or oxidation state 82 Chemical formulae 30 Oxidation-reduction reactions in Ionic bonding 32 terms of oxidation number 84 Covalent bonding 36 Using oxidation numbers to recognise redox Drawing dot and cross bonding diagrams 37 reactions 85 Metallic bonding 39 Oxidising and reducing agents 86 The structure and properties of solids 39 Tests for oxidising and reducing agents 88 Revision questions 43 Oxidation-reduction reactions in everyday activities 89 6 Chemica l equations 44 Revision question s 90 Writing balanced equations 44 11 Electrochemistry 91 Ionic equations 47 Revision questions 48 Predicting reactions using the electrochemical series of metals 91 7 Types of chemical reaction 49 Predicting reactions using the electrochemical Synthesis reactions 49 series of non-metals 92 Decomposition reactions 49 Electrical conduction 92 Single displacement reactions 49 Electrolysis 93 Ionic precipitation reactions 49 Electrolysis of molten electrolytes 95 Oxidation-reduction reactions 50 Electrolysis of aqueous electrolytes 95 Neutralisation reactions 50 Revision questions 99 Contents iii  Quantitative electrolysis 100 18 Characteristics of metals 155 Industrial applications of electrolysis 102 Physical properties of metals 155 Revision questions 105 Chemical properties of metals 155 12 Rates of reaction 106 Reactions of metal compounds 156 Revision questions 157 Measuring rates of reaction 106 The collision theory for chemical reactions 106 19 The reactivity, extraction and Rate curves for reactions 107 uses of metals 158 Factors that affect rates of reaction 107 The effect of changing different factors The reactivity series of metals 158 on rate curves 109 The extraction of metals from their ores 159 Revision questions 110 Extraction of aluminium 160 Extraction of iron 160 13 Energetics 111 Uses of metals 162 Exothermic and endothermic reactions 111 Alloys and uses of alloys 162 Breaking and forming bonds during reactions 111 Revision questions 164 Enthalpy changes during reactions 111 20 Impact of metals on living Energy profile diagrams 112 Calculating enthalpy changes 113 systems and the environment 165 Revision questions 116 Corrosion of metals 165 The importance of metals and Exam-style questions - Chapters 1 to 13 117 their compounds 14 Organic chemistry - an introduction 123 in living organisms 165 Harmful effects of metals and Bonding in organic compounds 123 The structure of organic molecules 124 their compounds 166 Formulae of organic compounds 124 Revision questions 167 Homologous series 125 21 Non-metals 168 Structural isomerism 126 The alkanes: CnH2n+2 128 Physical properties of non-metals 168 129 Chemical properties of non-metals 169 The alkenes: CnHzn Behaviour of non-metals as oxidising and Alcohols: CoH'o>,OH or R- OH 131 132 reducing agents 170 Alkanoic acids: CoH' o.,COOH or R-COOH Revision questions 132 Laboratory prepa·ration of gases 170 Uses of carbon dioxide and oxygen 172 15 Sources of hydrocarbon compounds 134 Uses of non-metals and their compounds 173 Harmful effects of non-metals and Natural sources of hydrocarbons 134 Fractional distillation of crude oil 134 their compounds 176 Cracking hydrocarbons 135 Revision questions 178 Revision questions n6 22 Water 179 16 Reactions of carbon compounds 137 The unique properties of water 179 137 Consequences of water's solvent properties 180 The alkanes: C n H2n +2 138 Treatment of water for domestic use 181 The alkenes: CoH,o Distinguishing between an alkane Revision questions 182 and an alkene 139 23 Green Chemistry 183 Uses of alkanes and alkenes 140 Revision questions 141 The twelve principles of Green Chemistry 183 141 Revision questions 184 Alcohols: CoH'o>,OH or R-OH Alkanoic acids: C" H,,,., COOH or R- COOH 143 24 Qualitative analysis 185 Esters: CnHzn+1COOCxH2x+l or R-COO-R' 143 145 Identifying cations 185 Soapy and soapless detergents Revision questions 147 Identifying anions 188 Identifying gases 190 17 Po lymers 148 Revision questions 191 Formation of polymers 148 Exam-style questions - Chapters 18 to 24 193 Uses of polymers 150 Appendix - The Periodic Table 196 Impact of synthetic polymers (plastics) , on the environment 150 Revision questions 151 Index 197 Exam-style questions - Chapters 14 to 17 152 Contents The pathway to success About this book This book has been written primarily as a revision course for students studying for the CSEC· Chemistry examination. The facts are presented concisely using a variety of fo rmats which makes them easy to understand and learn. Key words are highlighted in bold type and important definitions which must be learnt are written in italics and highlighted in colour. Annotated diagrams and tables have been used wherever possible and worked examples have been included where appropriate. Questions to help test knowledge and understanding, and provide practice for the actual examination, are included throughout the book. Th e following sections provide valuable information on the format of the CSEC· examination, how to revise successfully, successful examination technique, key terms used on examination papers and School-Based Assessment. The CSEC® Chemistry syllabus and this book The CSEC· Chemistry syllabus is available online at http://cxc-store.com. You are strongly advised to read through this syllabus carefully since it provides detailed information on the specific objectives of each topic of the course, School-Based Assessment (SBA) and the format of the CSEC· Examination. Each chapter in this book covers a particular topic in the syllabus. Chapters 1 to 13 cover topics in Section A, Principles of Chemistry Chapters 14 to 17 cover topics in Section B, Organic Chemistry Chapters 18 to 24 cover topics in Section C, Inorganic Chemistry At the end of each chapter, or section within a chapter, you will find a selection of revision questions. These questions test your knowledge and understanding of the topic covered in the chapter or section. At the end Chapters 13, 17 and 24 you will find a selection of exam-style questions which also test how you apply the knowledge you have gained and help prepare you to answer the different styles of questions that you will encounter in your CSEC· examination. You will find the answers to all these questions online at www.collins.co.uk/caribbeanschools. The format of the CSEC® Chemistry examination The examination consists of two papers and your performance is evaluated using the following three profiles: Knowledge and comprehension Use of knowledge Experimental skills The pathway to success V Paper 01 (1 % hours) Paper 01 consists of 60 multiple choice questions. Each question is worth 1 mark. Four choices of answer are provided for each question of which one is correct. Make sure you read each question thoroughly; some questions may ask which answer is incorrect. If you don't know the answer, try to work it out by eliminating the incorrect answers. Never leave a question unanswered. Paper 02 (2 Y, hours) Paper 02 is divided into Sections A and B, and consists of six compulsory questions, each divided into several parts. Take time to read the entire paper before beginning to answer any of the questions. Section A consists of three compulsory structured questions whose parts require short answers, usually a word, a sentence or a short paragraph. The answers are to be written in spaces provided on the paper. These spaces indicate the length of answer required and answers should be restricted to them. Question 1 is a data-analysis question which is worth 25 marks. The first part usually asks you to take readings from a measuring instrument, such as a set of thermometers, and record these readings in a table. You may then be asked to draw a graph using the information in the table and may be asked questions about the graph or be asked to perform certain calculations. The second part will possibly test your knowledge of tests to identify cations, anions and gases, and there may be a third part which tests your planning and designing skills. Questions 2 and 3 are each worth 15 marks. They usually begin with some kind of stimulus material, such as a diagram or a table, which you will be asked questions about. Section B consists of three compulsory extended-response questions, each worth 15 marks. These questions require a greater element of essay writing in their answers than those in Section A. The marks allocated for the different parts of each question are clearly given. A total of 100 marks is available for Paper 02 and the time allowed is 150 minutes. You should allow about 35 minutes for the data-analysis question worth 25 marks and allow about 20 minutes for each of the other questions. This will allow you time to read the paper fully before you begin and time to check over your answers when you have finished. Successful revision The following should provide a guide for successful revision. Begin your revision early. You should start your revision at least two months before the examination and should plan a revision timetable to cover this period. Plan to revise in the evenings when you don't have much homework, at weekends, during the Easter vacation and during study leave. , The oathwav to surrp~~  When you have a full day available for revision, consider the day as three sessions of about three to four hours each, morning, afternoon and evening. Study during two of these sessions only, do something non-academic and relaxing during the third. Read through the topic you plan to learn to make sure you understand it before starting to learn it; understanding is a lot safer than thoughtless learning. Try to understand and learn one topic in each revision session, more if topics are sho rt and fewer if topics are long. Revise every topic in the syllabus. Do not pick and choose topics since all questions on your exam paper are compulsory. learn the topics in order. When you have learnt all topics once, go back to the first topic and begin again. Try to cover each topic several times. Revise in a quiet location without any form of distraction. Sit up to revise, preferably at a table. Do not sit in a comfy chair or lie on a bed where you can easily fall asleep. Obtain copies of past CSEC® Chemistry examination papers and use them to practise answering exam-style questions, starting with the most rec;e,iit papers. These can be purchased online from the CXC Store.. You can use a variety of different methods to learn your wink. Chose which ones work best for you. Read the topic several times, then close the book and try to write down the main points. Do not try to memorise your work word for word since work learnt by heart is not usually understood and most questions test understanding, not just the ability to repeat facts. Summarise the main points of each topic on flash cards and use these to hel p you study. Draw simple diagrams with annotations, flow charts and spider diagrams to summarise topics in visual ways which are easy to learn. Practise drawing and labelling simple line diagrams of apparatus you have encountered. You may be asked to reproduce these, e.g. the apparatus used for fractional distillation. Practise writing equations. Do not try to learn equations by heart; instead, understand and learn how to write and balance them. For example, if you learn that a carbonate reacts with an acid to form a salt, carbon dioxide and water, you can write the equation for any carbonate reacting with any acid. Use memory aids such as: - acronyms, e.g. Oil RIG for oxidation and reduction in terms of electrons; oxidation is loss, reduction is gain. - mnemonics, e.g. 'Peter sometimes collects money at zoos in london helping crazy monkeys and silly giraffes' for the order of metals in the reactivity series; potassium, sodium, calcium, magnesium, aluminium, zinc, iron, (hydrogen), copper, mercury, silver, gold. - associations between words, e.g. anions - negative (therefore cations must be positive). Test yourself using the questions throughout this book and others from past CSEC®examination papers. The pathway to success vii Successful examination technique o Read the instructions at the start of each paper very carefully and do precisely what they requ ire. o Read through the entire paper before you begin to answer any of the questions. o Read each question at least twice before beginning your answer to ensure you understand what it asks. o Underline the important words in each question to help you answer precisely what the question is asking. oRe-read the question when you are part way through your answer to check that you are answering what it asks. o Give precise and factual answers. You will not get marks for information which is 'padded out' or irrelevant. The number of marks awarded for each answer indicates how long and detailed it should be. o Use correct scientific terminology throughout your answers. o Balance all chemical equations and ensu re that you give the correct state symbols, especially in ionic equations. o Show all working and give clear statements when answering questions that require calculations. o Give every numerical answer the appropriate unit using the proper abbreviation/ symbol e.g. cm ' , g, 0c. o If a question asks you to give a specific number of points, use bullets to make each separate point clear. o If you are asked to give similarities and differences, you must make it clear which points you are proposing as similarities and which points as differences. The same applies if you are asked to give advantages and disadvantages. o Watch the time as you work. Know the time available for each question and stick to it. o Check over your answers when you have completed all the questions, especially those requiring calculations. o Remain in the examination room until the end of the examination and recheck your answers again if you have time to ensure you have done your very best. Never leave the examination room early. Some key terms used on examination papers Account for: provide reasons for the information given. Calculate: give a numerical so lu tion which includes all relevant working. Compare: give similarities and differences. Construct: draw a graph or table using data provided or obtained. Contrast: give differences. The pathway to success Deduce: use data provided or obtained to arrive at a conclusion. Define: state concisely the meaning of a word or term. Describe: provid e a detailed account which includes all relevant information. Determine: find a solution using the information provided, usually by performing a ca lculation. Discuss: provide a balanced argument which considers points both for and against. Distinguish between or among: give differences. Evaluate: determine the significance or worth of the point in question. Explain: give a clear, detailed account which makes given information easy to understand and provides reasons for the information. Illustrate: make the answer clearer by including examples or diagrams. Justify: provide adequate grounds for your reasoning. Outline: write an account which includes the main points only. Predict: use information provided to arrive at a likely conclusion or suggest a possible outcome. Relate: show connections between different sets of information or data. State or list: give brief, precise facts without detail. Suggest: put forward an idea. Tabulate: construct a table to show information or data which has been given or obtained. Drawing tables and graphs Tables Tables can be used to record numerical data, observations and inferences. When drawing a table: o Neatly enclose the table and draw vertical and horizontal lines to separate columns and rows. o When drawing numerical tables, give th e correct column headings which state the physical quantities measured and give th e correct units using proper abbreviations/ symbols, e.g. cm J , g, aC. o Give the appropriate number of decimal places when recording numerical data. o When drawing non-numerical tables, give the correct column headings and all observations. o Give the table an appropriate title which must include reference to the responding variable and the manipulated variable. The pathway to success ix Graphs Graphs are used to display numerical data. When drawing a graph: o Plot the manipulated variable on the x-axis and the responding variable on the y-axis. o Choose appropriate scales which are easy to work with and use as much of the graph paper as possible. o Enter numbers along the axes and label each axis, including relevant units, e.g. cm 3, g, oc. o Use a small dot surrounded by a small circle to plot each point. o Plot each point accurately. o Drawa smooth curve or straight line of best fit which need not necessarily pass through all the points. o Give the graph an appropriate title which must include reference to the responding variable and the manipulated variable. School-Based Assessment (SBA) School-Based Assessment (SBA) is an integral part of your CSEC· examination. It assesses you in the Experimental Skills and Analysis and Interpretation involved in laboratory and field work, and is worth 20% of you r final examination mark. o The assessments are carried out in your school by your teacher during Terms 1 to 5 of your two-year programme. o The assessments are carried out during normal practical classes and not under examination conditions. You have every opportunity to gain a high score in each assessment if you make a consistent effort throughout you r two-year programme. o Assessments will be made of the following four skills: Manipulation and Measurement Observation, Recording and Reporting Planning and Designing Analysis and Interpretation As part of your SBA, you will also carry out an Investigative Project during the second year of your two-year programme. This project assesses your Planning and Designing, and Analysis and Interpretation skills. If you are studying two or three of the single science subjects, Biology, Chemistry and Physics, you may elect to carry out ONE investigation only from anyone of these subjects. You will be required to keep a practical workbook in which you record all of your practical work and this may then be moderated externally by Cxc. The pathway to success 1 The states of matter Chemistry is the study of the composition, structure, properti es and reaction s of matter. Everything around us is made of matter. Malter /s anything thai has volume and mcp.;s. All matter is made of particles and can exist in three different states: The solid state The liquid state The gaseous state The particulate theory of matter There are four main ideas behind the particulate theory of matter: A ll matter is composed of particles. The particles are in constant motion and temperature affects their speed of motion. The particles have empty spaces between them. The particles have forces of attraction betwee n them. Evidence to support the particulate theory of matter The processes of diffusion and osmosis provide evidence to suppo rt the fact that all matter is made of particles. Diffusion D iffusion is the net mon.' tnenl of particles from a region of hiR/H'f concentration to d region of lo\\'er wneenlrallOn, unlitlh" pdrlic/cs are evenly d"lniJuleci. Particl es in gases and liquids are capable of diffusing. Exa mple 1 When pieces of cotton wool soa ked in concentrated ammonia so lution and concentrated hydrochloriC acid are placed simultaneously at opposite ends of a glass tub e, a white ring of ammonium chloride form s inside the tub e. Ammonia so lution gives off ammonia gas and hydroch loriC acid gives off hydrogen chloride gas. The particles of the gases diffuse throu gh the air inside the tube, co llide and react to form amm onium chloride: ammonia + hydrogen ch loride ammonium chloride NH,(g) + HCI(g) NH, CI(s) Ammonia particles diffuse faster than hydrogen chloride particl es, so the particles co llide and react close r to the source of the hydrogen chloride particles. 1 ammonia particles 2 hydrogen chloride diffuse very quickly particles diffuse quickly along the lube along the tube cotion wool soaked in ~ iI...,..':,---"\C------~ -t ~ { cotion woolsoaked in concentrat~d ~ ~.... concentrated ammOnia _~ _ ,, _ hydrochloric solution I acid 3 ammonia and hydrogen chloride particles collide, react and form a ring of white ammonium chloride Figure 1.1 Gases diffus e 1 The states of matter Example 2 When a purple potassium manganate(VII) crystal is placed in water, it dissolves to produce a uniformly purpl e solution. The particles making up the crystal separate from each oth er and diffuse through the spaces between the water particles until they are even ly distributed. purple potassium manganate(VlI) solution gradually forms 1 water particles move randomly and have small spaces 3 crystal particles between gradually separate from each other and diffuse into the spaces between the water water particles 2 crystal particles potassium packed tightly manganate(VII) -+-- together crystal before dissolving during dissolving Figure 1.2 Crystals dissolve Osmosis Osmosis is the movement of water molecules through a differentially permeable membrane from a solution containing a lot of wa ter molecules, e.g. a dilute solution (or \valer), Lo a solution containing fewer water molecules, e.g. a concentrated soluUon. Example 1 When a dilute sucrose solution is separated from a conce ntrated suc ros e solution by a differentially permeable membrane, water molecules move through the membrane from the dilute solution into the concentrated solution, but the sucrose molecules cannot move in the other direction. The volume of the concentrated solution increases and the volume of the dilute so lution decreases. glass tube - -- ----1 o 3 the level 01 the concentrated o solution rises due to its increased volume , differentially permeable membrane - has minute 2 sucrose particles pOres which only allow try to diffuse through the water particles through membrane into the dilute solution. but they are unable to pass through the pores o 1 water particles diffuse o· through the pores in the membrane into the concentrated solution causing its volume to concentrated Increase sucrose solution Figure 1.3 'Osmosis explained 1 Concise Revision Course: CSEC· Chemistry Exa mpl e 2 The membranes of living cells are differentially permeable and the cytoplasm inside the cells contains abo ut 80% water. When a strip of living tissue (such as paw-paw) is placed in water, water molecules move into the cells by osmosis. Each cell swells slightly, and the strip increases in length and becomes rigid. When the strip is placed in a concentrated sodium chloride solution, water molecules move out of the cells by osmosis. Each cell shrinks slightly, and the strip decreases in length and becomes softer. Uses of osmosis To control garden pests Slugs and snails are garden pests, whose skin is differentially permeable and always moist. When salt (sodium chloride) is sprinkled on slugs and snails, it dissolves in the moisture around their bodies forming a concentrated solution. Water inside their bodies then moves out by osmosis and into the solution. The slugs and snails die from dehydration if their bodies lose more water than they can tolerate. To preserve food Salt and sugar are used to preserve foods such as meat, fish and fruit. They both work in the same way: They draw water out of the cells of the food by osmosis. This prevents the food from decaying because there is no water available in the cells for the chemical reactions which cause the decay. They draw water out of microorganisms (bacteria and fungi ) by osmosis. This prevents the food from decaying because it inhibits the growth of the microorganisms that cause the decay. Types of particles that make up matter There are three different typ es of particles that make up matter: Atoms Atoms are the smallest units of a chemical element which have all the characteristics of the element. For example, iron is made of iron atoms, Fe (see p. 7). Molecules Molecules are groups of two or more atoms bonded together and which can exist on their own. Molecules may be made up of atoms of the same kind, e.g. hydrogen molecules, H" are mad e up of hydrogen atoms, H. Molecules may also be made up of atoms of different kind s, e.g. carbon dioxide molecules, CO" are made up of carbon atoms, C, and oxygen atoms, ° (see p. 36). Ions Ions are electrically charged particles. Ions may be formed from a single atom, e.g. the potassium ion, K'. They may also be formed from groups of two or more atoms bonded together, e.g. the nitrate ion, NO,' (see p. 34). 1 The states of matter The three states of matter The particulate theory of matter helps explain the physical properties of matter and th e differences between the three states. Table 1.1 Comparing the three states of matter 'I' Shape Fixed. Takes the shape of the Takes the shape of the entire part of the container it is container it is in. in. The surface is always horizontal. Volume Fixed. Fixed. Variable - it expands to fill the container it is in. Density Usually high. Usually lower than solids. Low. Compressibility Difficult to Can be compressed Very easy to compress. compress. very slightly by applying pressu reo Arrangement of Packed closely Have small spaces Have large spaces between particles together, usually between and are and are randomly arranged: in a regular way: randomly arranged: i \ Forces of attraction Strong. Weaker than those Very weak. between the particles between the particles in a solid. Energy possessed by Possess very Possess more kinetic Possess large amounts of the particles small amounts of energy that the particles kinetic energy. kinetic energy. in a solid. Movement of the Vibrate in their Move slowly past each Move around freely and particles fixed position. other. rapidly. Changing state Matter can exist in any of the three states depending on its temperature. It can change from one state to another by heating or cooling, as this causes a change in the kinetic energy and arrangement of the particles: When a so lid is heated, it usually changes state to a liquid and then to a gas. This occurs because the particles gain kinetic energy, move increasingly faster and further apart, and the forces of attraction between them become increasingly weaker. When a gas is cooled, it usually changes state to a liquid and then to a solid. This occurs because the particles lose kinetic energy, move more and more slowly and closer together, and the forces of attraction between them become increasingly stronger. 1 Concise Revision Course: CSEC· Chemistry  add heat evaporation/ melting boiling SOLID LIQUID GAS I freezing condensation I sublimation deposItion remove heat Figure 1.4 Changing state Evaporation and boiling are different in the following ways: Evaporation can take place at any temperature, whereas boiling occurs at a specific temperature. Evaporation takes place at the surface of the liquid only, whereas boiling takes place throughout the liquid. Substances which sublimate (or sublime) change directly from a solidi o a gas. The reverse process in which a gas changes directly to a solid is called deposition. Examples of substances that sublimate include carbon dioxide ('dry ice'), iodine and naphthalene (moth balls). Heating and cooling curves A heating curve is drawn when the temperature of a solid is measured at intervals as it is heated and changes state to a liquid and then to a gas, and the temperature is then plotted against time. A cooling curve is drawn when the temperature of a gas is measured at intervals as it is cooled and changes state to a liquid and then to a solid, and the temperature is then plotted against time. gas liquid and gas ,---"...:.c..==J.......-- boiling point - temperature stays constant until the liquid has all boiled (or the gas has all liquid condensed) solid and liquid ,-----'---'-