Topical revision notes chemistry o level by samantha l ellis

O Level Chemistry Topical Revision Notes is a comprehensive guide based on the latest syllabus It is written to provide candidates sitting for the O Level Chemistry examination with thorough revision material Important concepts are presented in simple and concise points for easier reference Relevant examples and diagrams are incorporated into the notes to facilitate the understanding of important concepts C M Y CM MY O Level Topical Revision Notes Series: Mathematics Additional Mathematics Physics Chemistry Biology Science Physics Science Chemistry Science Biology Topical REVISION NOTES CHEMISTRY Samantha L Ellis MSc, PGDE, BSc CY CMY K Includes ü Comprehensive Revision Notes ü Effective Study Guide ISBN 978 981 288 017 ü Periodic Table CHEMISTRY Samantha L Ellis MSc, PGDE, BSc SHINGLEE PUBLISHERS PTE LTD 120 Hillview Avenue #05-06/07 Kewalram Hillview Singapore 669594 Tel: 6760 1388 Fax: 6762 5684 e-mail: info@shinglee.com.sg http://www.shinglee.com.sg All rights reserved No part of this publication may be reproduced in any form or 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 Publishers First Published 2016 ISBN 978 981 288 017 Printed in Singapore PREFACE O Level Chemistry Topical Revision Notes has been written in accordance with the latest syllabus issued by the Ministry of Education (Singapore) This book is divided into 23 topics, each covering a topic as laid out in the syllabus Important concepts are highlighted in each topic, with relevant examples and diagrams to help students learn how to apply theoretical knowledge We believe this book will be of great help to teachers teaching the subject and students preparing for their O Level Chemistry examination Preface  iii CONTENTS Periodic Table v Topic Kinetic Particle Theory Topic Experimental Techniques Topic Methods of Purification Topic Elements and Compounds 10 Topic Atoms and Ions 11 Topic Chemical Bonding 13 Topic Structure of Matter 16 Topic Writing Formulae and Equations 19 Topic Stoichiometry and Mole Concept 20 Topic 10 Acids and Bases 23 Topic 11 Salts 27 Topic 12 Oxidation and Reduction 32 Topic 13 Metals 34 Topic 14 Electrolysis 41 Topic 15 Periodic Table 45 Topic 16 Energy Changes 49 Topic 17 Speed of Reaction 52 Topic 18 Ammonia 55 Topic 19 Air and Atmosphere 57 Topic 20 Introduction to Organic Chemistry 61 Topic 21 Alkanes and Alkenes 64 Topic 22 Alcohols and Carboxylic Acids 67 Topic 23 Macromolecules 70 iv  Contents Periodic Table  v Mg Magnesium Na Sodium Calcium Strontium 45 Zr 91 Titanium Radium 89 Key b X a 227 actinium Ac † b = proton (atomic) number X = atomic symbol a = relative atomic mass *58–71 Lanthanoid series †90–103 Actinoid series 88 Francium 87 Ra Fr 226 Hf * Hafnium La 57 Lanthanum Ba Barium Cs 55 Caesium 72 40 Zirconium 22 178 Yttrium Y 89 48 Ti 139 39 21 Scandium Sc 137 56 38 Rubidium 133 Sr Rb 37 88 85 20 Potassium 19 40 Ca K 12 24 Beryllium 23 Lithium 39 11 Be II Li I Ta 181 Niobium Nb 93 90 58 73 52 Mo 96 W 184 Pr Praseodymium Cerium 55 Tc Ru 190 U 92 238 Uranium Pa Protactinium 232 93 Neptunium Np Promethium 61 Neodymium 60 Pm Nd 144 Os 76 44 Osmium 75 Th 91 Iron 101 Ruthenium 26 56 Fe Re 186 27 59 28 59 29 64 30 65 16 VI 19 VII Sm 150 Iridium Ir 192 94 Pu Plutonium 62 Samarium 77 45 Rhodium Rh 103 Cobalt Co Pt 195 152 Eu 95 Am Americium 63 Europium 78 Platinum 46 Palladium Pd 106 Nickel Ni Gd 157 Gold Au 197 Silver 96 64 Curium Cm Gadolinium 79 47 Ag 108 Copper Cu Bk Terbium Tb 159 Mercury Hg 201 97 Berkelium 65 80 48 Cadmium Cd 112 Zinc Zn 70 Dy 163 Thallium Tl 204 Indium In 115 Gallium Ga 98 Cf Californium 66 Dysprosium 81 49 31 13 Aluminium Al 27 Boron B Ge 73 Silicon Ho 165 Lead Pb 207 Tin Sn 119 99 Es Einsteinium 67 Holmium 82 50 32 Germanium 14 Si 28 Carbon C 75 Sb 122 Arsenic As Fm Erbium Er 167 Bismuth Bi 209 100 Fermium 68 83 51 Antimony 33 15 Phosphorus P 31 Nitrogen N Se 79 Sulfur Te 128 Po 169 Md Thulium Tm 101 Mendelevium 69 84 Polonium 52 Tellurium 34 Selenium 16 S 32 Oxygen O Yb 173 Astatine At Iodine I 127 Bromine Br 80 Chlorine 102 No Nobelium 70 Ytterbium 85 53 35 17 Cl 35.5 Fluorine F Lr Lutetium Lu 175 Radon Rn Xenon Xe 131 Krypton Kr 84 Argon Ar 40 Neon 103 Lawrencium 71 86 54 36 18 10 Ne 20 He 14 V Helium 12 IV H 11 III Hydrogen Rhenium 43 Technetium 25 Manganese Mn Thorium 59 141 140 74 Tungsten 42 Molybdenum 24 Chromium Cr Ce Tantalum 41 23 Vanadium V 51 1 Group TOPIC Kinetic Particle Theory Objectives Candidates should be able to: (a) describe the solid, liquid and gaseous states of matter and explain their interconversion in terms of the kinetic particle theory and of the energy changes involved (b) describe and explain evidence for the movement of particles in liquids and gases (c) explain everyday effects of diffusion in terms of particles (d) state qualitatively the effect of molecular mass on the rate of diffusion and explain the dependence of rate of diffusion on temperature Kinetic Particle Theory All matter is made of particles which are in constant random motion This accounts for the properties of the three states of matter and the changes of states Properties of the Three States of Matter Property Solid Liquid Gas Structure Packing of particles Tightly packed Arranged in an orderly manner Packed closely together, but not as tightly as in solids No regular arrangement Spaced far apart from each other Movement of particles Can only vibrate about fixed positions Particles slide past each other Particles move freely at high speeds Shape Fixed shape No fixed shape Takes on the shape of the container it is in No fixed shape Takes on the shape of the container it is in Volume Fixed volume Not easily compressed Fixed volume Not easily compressed No fixed volume Easily compressed Kinetic Particle Theory Changes of State SOLID ti el m ng g zin e fre LIQUID de po su bli m condensation sit ion at ion GAS boiling/evaporation The following diagram shows the temperature change when a substance undergoes changes in state temperature/ºC liquid + gas boiling point gas liquid melting point solid + liquid solid time/s At parts where the graph rises, heat is supplied to the substance to raise its temperature The graph becomes flat when the substance undergoes a change in state The graph remains flat as heat is taken in to overcome the interactions between the particles TOPIC The suffix of the name of an organic compound tells us which homologous series the compound belongs to Homologous series Suffix Alkanes -ane Alkenes -ene Alcohols -ol Carboxylic acids -oic acid Isomers Isomers are compounds which have the same chemical formula but different structural formulae They could belong to different homologous series They usually share the same chemical properties but differ in physical properties Fractional Distillation of Petroleum Petroleum is a mixture of hydrocarbons which can be separated into various useful fractions through fractional distillation Petroleum is first passed through a furnace to be heated into a vapour The vapour is then passed through the fractionating column Since petroleum consists of hydrocarbons of different sizes, the fractions have different boiling points and condense at different temperatures The vapour rises up the column where they will condense and be tapped off Higher parts of the column have lower temperatures while lower parts of the column have higher temperatures Since lighter fractions have lower boiling points, they are tapped off at higher parts of the column Heavier fractions on the other hand, have higher boiling points and are tapped off at lower parts of the column A simplified diagram of the fractional distillation of petroleum and the fractions collected is shown Petroleum gas Petrol (gasoline) Furnace Petroleum Fractionating Vapour column Naphtha Kerosene (paraffin) Diesel oil Lubricating oil Bitumen 62 TOPIC 20 Fractions of Petroleum and Their Uses Fraction Boiling point range (°C) Uses Petroleum gas Below 40 Fuel for domestic use (cooking, heating) Petrol (gasoline) 40 to 75 Fuel for cars Naphtha 90 to 150 Feedstock for chemical industries Kerosene (paraffin) 150 to 240 Fuel for aircraft engines; Fuel for cooking and heating Diesel oil 220 to 250 Fuel for heavy vehicles Lubricating oil 300 to 350 For lubricating machine parts; Making waxes and polishes Bitumen Above 350 For road surfaces; Roofing As smaller fractions can be used as fuel and chemical feedstock, the demand for smaller fractions is generally higher than that of larger fractions such as bitumen To meet these demands, larger fractions are cracked to form smaller hydrocarbon molecules Introduction to Organic Chemistry 63 TOPIC Alkanes and Alkenes 21 Objectives Candidates should be able to: (a) describe an homologous series as a group of compounds with a general formula, similar chemical properties and showing a gradation in physical properties as a result of increase in the size and mass of the molecules, e.g melting and boiling points; viscosity; flammability (b) describe the alkanes as an homologous series of saturated hydrocarbons with the general formula CnH2n+2 (c) draw the structures of branched and unbranched alkanes, C1 to C4, and name the unbranched alkanes methane to butane (d) define isomerism and identify isomers (e) describe the properties of alkanes (exemplified by methane) as being generally unreactive except in terms of combustion and substitution by chlorine (f) describe the alkenes as an homologous series of unsaturated hydrocarbons with the general formula CnH2n (g) draw the structures of branched and unbranched alkenes, C2 to C4, and name the unbranched alkenes ethene to butene (h) describe the manufacture of alkenes and hydrogen by cracking hydrocarbons and recognise that cracking is essential to match the demand for fractions containing smaller molecules from the refinery process (i) describe the difference between saturated and unsaturated hydrocarbons from their molecular structures and by using aqueous bromine (j) describe the properties of alkenes (exemplified by ethene) in terms of combustion, polymerisation and the addition reactions with bromine, steam and hydrogen (k) state the meaning of polyunsaturated when applied to food products (l) describe the manufacture of margarine by the addition of hydrogen to unsaturated vegetable oils to form a solid product Alkanes Alkanes are saturated hydrocarbons with the general formula CnH2n+2, where n  Names of alkanes usually end with ‘-ane’ The first four members of the alkane homologous series are listed in the following table 64 Name Methane Ethane Propane Butane n Molecular formula CH4 C 2H C 3H C4H10 Moving down the series, the molecular size of the alkanes increases This means that the intermolecular forces of attraction become stronger This leads to an increase in melting and boiling points and an increase in viscosity down the series The flammability however decreases with an increase in molecular size of the alkanes TOPIC 21 Chemical Properties of Alkanes Alkanes are generally unreactive as C – C and C – H bonds are not easily broken They can only undergo combustion and substitution reactions Combustion occurs when an alkane combines with oxygen The reaction is exothermic and hence, alkanes are used as fuels and are burned for energy If the alkane burns in excess oxygen, complete combustion occurs to produce carbon dioxide and water only If the alkane burns under oxygen-deficient conditions, soot (carbon) and carbon monoxide are produced as well Alkanes can only react with halogens through substitution reactions This occurs in the presence of ultraviolet light Hydrogen atoms are substituted by halogen atoms in the reaction The reaction produces a mixture of halogen-containing compounds Alkenes Alkenes are unsaturated compounds with the general formula CnH2n, where n  2.Note that a 1-carbon alkene cannot exist Names of alkenes usually end with ‘-ene’ The first three members of the alkene homologous series are listed in the following table Name Ethene Propene Butene n Molecular formula C 2H   C 3H C 4H Chemical Properties of Alkenes Like alkanes, alkenes undergo complete combustion when there is sufficient oxygen to form carbon dioxide and water only They undergo incomplete combustion to produce soot and carbon monoxide Due to the higher carbon-to-hydrogen ratio, alkenes burn with a smokier flame than their corresponding alkanes Alkenes are called unsaturated compounds due to the presence of C = C bonds These bonds allow for alkenes to undergo addition reactions, which is a characteristic of alkenes Hydrogen gas can be added to an alkene to obtain an alkane This reaction occurs at 200 °C in the presence of nickel as a catalyst ethene + hydrogen → ethane C2H4(g) + H2(g) → C2H6(g) Margarine is produced by adding hydrogen to vegetable oils Vegetable oil contains many C = C bonds, hence it is described to be polyunsaturated One hydrogen molecule is added across each C = C bond in this process Alkanes and Alkenes 65 Halogens can be added across the C = C bond at room temperature and pressure to produce halogenoalkanes An example is the addition of bromine to an alkene ethene + bromine → dibromoethane C2H4(g) + Br2(aq) → C2H4Br2(aq) The addition of bromine is used in testing for the presence of unsaturated compounds Aqueous bromine is reddish-brown and becomes colourless when an unsaturated compound is added Alcohols can be produced from the addition of steam to alkenes This takes place at a temperature of 300 °C and pressure of 60 atm, in the presence of phosphoric(V) acid, which acts as a catalyst ethene + steam → ethanol C2H4(g) + H2O(g) → C2H5OH(l) Alkene molecules can also react with one another to form a large saturated molecule through addition polymerisation This process takes place at high temperature and pressure in the presence of a catalyst ethene → poly(ethene) n C2H4(g) → (C2H4)n(s) Cracking Large hydrocarbons can be broken down into smaller molecules through cracking This process requires aluminium oxide or silicon dioxide as catalyst 66 The mixture of large hydrocarbons is passed over the catalyst at a high temperature of about 600 °C These molecules are then broken down into a mixture of small alkanes and alkenes, and hydrogen is sometimes produced as well Small hydrocarbon molecules such as ethene are required as starting materials for petrochemical industries Cracking is important as it converts larger fractions of petroleum, which are of lower demand, into small hydrocarbons which are in high demand In addition, cracking provides the source of hydrogen for the production of ammonia in the Haber process TOPIC 21 TOPIC Alcohols and Carboxylic Acids 22 Objectives Candidates should be able to: (a) describe the alcohols as an homologous series containing the –OH group (b) draw the structures of alcohols, C1 to C4, and name the unbranched alcohols methanol to butanol (c) describe the properties of alcohols in terms of combustion and oxidation to carboxylic acids (d) describe the formation of ethanol by the catalysed addition of steam to ethene and by fermentation of glucose (e) state some uses of ethanol (f) describe the carboxylic acids as an homologous series containing the –CO2H group (g) draw the structures of carboxylic acids methanoic acid to butanoic acid and name the unbranched acids, methanoic acid to butanoic acid (h) describe the carboxylic acids as weak acids, reacting with carbonates, bases and some metals (i) describe the formation of ethanoic acid by the oxidation of ethanol by atmospheric oxygen or acidified potassium manganate(VII) (j) describe the reaction of a carboxylic acid with an alcohol to form an ester (k) state some commercial uses of esters Alcohols Alcohols are a homologous series of organic compounds that have the general formula CnH2n+1OH, where n  They have the functional group OH, which is also called the hydroxyl group Names of alcohols usually end with ‘-ol’ The first four members of the alcohol homologous series are listed in the following table Name Methanol Ethanol Propanol Butanol n Molecular formula CH3OH C2H5OH C3H7OH C4H9OH Alcohols are liquids at room temperature and pressure and are very volatile As the molecular sizes of the alcohols increases down the series, the forces of attraction between the molecules become stronger As a result, the melting and boiling points increase with larger molecular size Smaller alcohols are miscible in water As the molecular size of the alcohols increases, solubility in water decreases An important member of the homologous series is ethanol, which is used in food and drinks, as a solvent for paints and perfumes, and as fuel Alcohols and Carboxylic Acids 67 Chemical Properties of Alcohols Alcohols undergo complete combustion when there is sufficient oxygen to produce carbon dioxide and water When heated with oxidising agents such as acidified potassium manganate(VII), alcohols undergo oxidation to form carboxylic acids Production of Ethanol Ethanol used for human consumption is usually produced through fermentation of glucose from fruits or grains The process is carried out with yeast at 37 °C, in the absence of oxygen The temperature has to be kept at 37 °C as the enzymes in yeast work best at this temperature Increasing the temperature would denature the enzymes and cause them to be unable to catalyse the reaction Fermentation produces a dilute solution of ethanol High concentrations of ethanol cannot be obtained directly from this process as the yeast dies when the concentration of ethanol reaches about 15% Ethanol is also produced on a larger scale through the addition of steam to ethene This takes place at 300 °C and 60 atm in the presence of phosphoric(V) acid as a catalyst This process produces an ethanol solution of higher purity and concentration compared to fermentation Carboxylic Acids Alcohols are a homologous series of organic acids that have the general formula CnH2n+1COOH, where n  They have the functional group –COOH, which is also called the carboxyl group Names of carboxylic acids usually end with ‘-oic acid’ The first four members of the carboxylic acid homologous series are listed in the following table Name 68 Methanoic acid Ethanoic acid n Molecular formula HCOOH CH3COOH TOPIC 22 Propanoic acid Butanoic acid C2H5COOH C3H7COOH Chemical Properties of Carboxylic Acids Carboxylic acids are weak acids that partially dissociate in water to give hydrogen ions Due to the presence of these hydrogen ions when carboxylic acids dissolve in water, they undergo reactions of acids Carboxylic acids react with metals that lie above hydrogen in the reactivity series to produce salt and water ethanoic acid + magnesium → magnesium ethanoate + hydrogen 2CH3COOH(aq) + Mg(s) → (CH3COO)2Mg(aq) + H2(g) Carboxylic acids react with metal carbonates to produce salt, carbon dioxide and water ethanoic acid + calcium carbonate → calcium ethanoate + carbon dioxide + water 2CH3COOH(aq) + CaCO3(s) → (CH3COO)2Ca(aq) + CO2(g) + H2O(l) Carboxylic acids react with metal hydroxides to produce salt and water ethanoic acid + sodium hydroxide → sodium ethanoate + water CH3COOH(aq) + NaOH(aq) →CH3COONa(aq) + H2O(l) Esters Esters are sweet-smelling liquids that are used as solvents for perfumes or for making artificial food flavourings They can be produced through esterification from the reaction between alcohols and carboxylic acids Esterification requires heating an alcohol and a carboxylic acid with a few drops of concentrated sulfuric acid as a catalyst This process is a reversible reaction as indicated by the  symbol H H O C C H O H ethanoic acid H H O C H methanol H H H O C C H H O C H + H2O H methyl ethanoate water Apart from acting as a catalyst in the reaction, concentrated sulfuric acid is a dehydrating agent and removes water produced This also helps speeding up the rate of product formation Note that there are two parts to the name of an ester The first part of the name is taken from the alcohol while the second part is taken from the carboxylic acid from which it is made Alcohols and Carboxylic Acids 69 TOPIC Macromolecules 23 Objectives Candidates should be able to: (a) describe macromolecules as large molecules built up from small units, different macromolecules having different units and/or different linkages (b) describe the formation of poly(ethene) as an example of addition polymerisation of ethene as the monomer (c) state some uses of poly(ethene) as a typical plastic (d) deduce the structure of the polymer product from a given monomer and vice versa (e) describe nylon, a polyamide, and Terylene, a polyester, as condensation polymers, the partial structure of nylon being represented as O O C C N N H H O O C C N N H H and the partial structure of Terylene as O O C C O O O O C C O O (f) state some typical uses of man-made fibres such as nylon and Terylene (g) describe the pollution problems caused by the disposal of non-biodegradable plastics Polymers A polymer is a very large molecule that consists of many smaller molecules joined together by covalent bonds These smaller units that make up the polymer are also called monomers Addition Polymerisation Addition polymerisation occurs for unsaturated monomers The reaction takes place under high temperature and pressure in the presence of a catalyst 70 The process involves breaking the C = C bond so that the monomers can form bonds with other monomers No atom or molecule is lost in this process, so the empirical formula of the addition polymer is the same as its monomer Poly(ethene) is produced through the addition polymerisation of ethene It is used in making plastic bags and clingfilm TOPIC 23 Condensation Polymerisation Condensation polymerisation involves joining of monomers with the loss of a small molecule for each linkage formed Nylon is a polyamide that has monomers joined together by amide linkages It is formed from dicarboxylic acids and diamines The formation of an amide linkage between the carboxyl and amine groups results in the loss of a water molecule O H O C O H H O C O H H N N H → H O C O H C N N H + H 2O H Terylene is a polyester that has monomers joined together by ester linkages It is formed from dicarboxylic acids and diols The formation of an ester linkage between the carboxyl and hydroxyl groups results in the loss of a water molecule Nylon and Terylene are both used to make clothing, curtains, fishing lines, parachutes and sleeping bags O H O C O C O H H O O O H → H O C O C O O H + H 2O Macromolecules 71 NOTES NOTES NOTES O Level Chemistry Topical Revision Notes is a comprehensive guide based on the latest syllabus It is written to provide candidates sitting for the O Level Chemistry examination with thorough revision material Important concepts are presented in simple and concise points for easier reference Relevant examples and diagrams are incorporated into the notes to facilitate the understanding of important concepts C M Y CM MY O Level Topical Revision Notes Series: Mathematics Additional Mathematics Physics Chemistry Biology Science Physics Science Chemistry Science Biology Topical REVISION NOTES CHEMISTRY Samantha L Ellis MSc, PGDE, BSc CY CMY K Includes ü Comprehensive Revision Notes ü Effective Study Guide ISBN 978 981 288 017 ü Periodic Table ... while oxidation occurs at the anode The electrolyte contains mobile ions which allow for electricity to flow through It is usually an acid solution, or an ionic compound that is molten or dissolved... H O H C O H water, H 2O C methane, CH4 electron of oxygen electron of hydrogen carbon dioxide, CO2 electron of carbon electron of hydrogen electron of oxygen electron of carbon Covalent bonds... The outermost electron shell is also called the valence electron shell TOPIC TOPIC Chemical Bonding Objectives Candidates should be able to: (a) describe the formation of ions by electron loss/gain