Cambridge CIE IGCSE Chemistry PDF

Head to www.savemyexams.com for more awesome resources Cambridge (CIE) IGCSE Your notes Chemistry Organic Families Contents Fossil Fuels Alkanes Alkenes Addition Reactions Alcohols Carboxylic Acids Etha...

Head to www.savemyexams.com for more awesome resources Cambridge (CIE) IGCSE Your notes Chemistry Organic Families Contents Fossil Fuels Alkanes Alkenes Addition Reactions Alcohols Carboxylic Acids Ethanoic Acid & Esterification Reactions Page 1 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Fossil Fuels Your notes Common fossil fuels A fuel is a substance which when burned, releases heat energy This heat can be transferred into electricity, which we use in our daily lives Most common fossil fuels include coal, natural gas and petroleum Methane, CH4, is the main constituent of natural gas and is a hydrocarbon Hydrocarbons are made from hydrogen and carbon atoms only Petroleum & fractional distillation Petroleum Petroleum is also called crude oil and is a mixture of hydrocarbons which also contains natural gas It is a thick, sticky, black liquid that is found under porous rock (under the ground and under the sea) The location of crude oil Page 2 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Crude oil is located under the sea Petroleum itself as a mixture isn't very useful but each component part of the mixture, called a fraction, is useful and each fraction has different applications Fractional distillation Each fraction consists of groups of hydrocarbons of similar chain lengths Page 3 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources The fractions in petroleum are separated from each other in a process called fractional distillation The molecules in each fraction have similar properties and boiling points, which depend on the Your notes number of carbon atoms in the chain The size of each molecule is directly related to how many carbon and hydrogen atoms the molecule contains Most fractions contain mainly alkanes, which are compounds of carbon and hydrogen with only single bonds between them Diagram to show fractional distillation The process separates the fractions according to their boiling point Fractional distillation is carried out in a fractionating column which has a temperature gradient Page 4 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources It is very hot at the bottom of the column and cooler at the top During the process of fractional distillation: Your notes The crude oil is heated and vapourises The vapours of hydrocarbons enter the column which has a temperature gradient The vapours of hydrocarbons with high boiling points condense at the bottom of the column The vapours of hydrocarbons with lower boiling points rise up the column and condense at the top Properties of fractions Viscosity This refers to the ease of flow of a liquid. High viscosity liquids are thick and flow less easily. As the number of carbon atoms increases, the attraction between the hydrocarbon molecules also increases which results in the liquid becoming more viscous with the increasing length of the hydrocarbon chain. Going down the column, the viscosity of the fractions increases Melting point/boiling point As the molecules get larger, the intermolecular attraction becomes greater. More heat is needed to separate the molecules. Going down the column, the boiling points of the fractions increases Volatility Volatility refers to the tendency of a substance to vaporise. As the size of the hydrocarbon increases liquids the attraction between the molecules increases Going down the column, the volatility of the fractions therefore decreases Uses of Fractions Refinery gas: heating and cooking Gasoline: fuel for cars (petrol) Naphtha: raw product for producing chemicals Kerosene: for making jet fuel (paraffin) Diesel: fuel for diesel engines (gas oil) Page 5 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Fuel oil: fuel for ships and for home heating Lubricating oil: for lubricants, polishes, waxes Your notes Bitumen: for surfacing roads Table to show the trends in properties Fraction Number of Boiling point Viscosity Volatility carbon atoms range / oC Refinery gas 1-4 Below 25 Viscosity increases Volatility decreases going down the going down the fractions Gasoline / 4-12 40-100 fractions petrol Naptha 7-14 90-150 Kerosene / 12-16 150-240 paraffin Diesel / gas 14-18 220-300 oil Fuel oil 19-25 250-320 Lubricating oil 20-40 300-350 Bitumen More than 70 More than 350 Examiner Tips and Tricks You must be able to recall a use for each fraction as well describe the trends in properties. Page 6 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Alkanes Your notes Alkanes: properties & bonding What is an alkane? Alkanes are a group of saturated hydrocarbons The term saturated means that they only have single carbon-carbon bonds, there are no double bonds Alkanes have covalent bonds as they consist of non-metal atoms The general formula of the alkanes is CnH2n+2 Table of alkanes Displayed formula Name Molecular formula methane CH4 ethane C2 H 6 propane C3H 8 Page 7 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources butane C4H10 Your notes pentane C5H12 The first five members of the alkane homologous series Examiner Tips and Tricks Co-ordinated students only need to be able to name and draw the displayed formula for methane and ethane but extended students should know the whole table. Alkanes are colourless compounds which have a gradual change in their physical properties as the number of carbon atoms in the chain increases They are generally unreactive compounds but they: Undergo combustion Can be cracked into smaller molecules React with halogens in the presence of light in substitution reactions Combustion of alkanes Alkanes undergo complete combustion to form carbon dioxide and water: Alkane + oxygen → carbon dioxide + water Combustion of methane: CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (l) Page 8 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Combustion of ethane: C2H6 (g) + 3½O2 (g) → 2CO2 (g) + 3H2O (l) Your notes Combustion of propane: C3H8 (g) + 5O2 (g) → 3CO2 (g) + 4H2O (l) Combustion of butane: C4H10 (g) + 6½O2 (g) → 4CO2 (g) + 5H2O (l) Substitution reaction of alkanes with halogens Extended tier only In a substitution reaction, one atom (or group of atoms) is swapped with another atom (or group of atoms) Alkanes undergo a substitution reaction with halogens in the presence of ultraviolet radiation (sunlight is a source of UV radiation) This is called a photochemical reaction The UV light provides the activation energy, Ea, for the reaction A hydrogen atom is replaced with the halogen atom More than one hydrogen atom can be substituted depending on the amount of ultraviolet radiation there is In the presence of ultraviolet (UV) radiation, methane reacts with chlorine to form chloromethane and hydrogen chloride Examiner Tips and Tricks Page 9 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources You need to be able to draw the displayed and structural formulae of the products formed when chlorine replaces one hydrogen atom (also known as monosubstitution) Your notes Page 10 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Alkenes Your notes Catalytic cracking Alkenes are unsaturated hydrocarbons with carbon-carbon double bonds (C=C) They have covalent bonds Their general formula is CnH2n The presence of the double bond, C=C, means they can make more bonds with other atoms by opening up the C=C bond and allowing incoming atoms to form another single bond with each carbon atom of the functional group Each of these carbon atoms now forms 4 single bonds instead of 1 double and 2 single bonds This makes them much more reactive than alkanes Table of alkenes Displayed formula Name Molecular formula ethene C2 H 4 propene C3H 6 Page 11 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources but-1- C 4H 8 ene Your notes pent-1- C5H10 ene The first four members of the alkene homologous series Manufacture of alkenes Although there is use for each fraction obtained from the fractional distillation of crude oil, the amount of longer chain hydrocarbons produced is far greater than needed These long chain hydrocarbon molecules are further processed to produce other products A process called catalytic cracking is used to convert longer-chain molecules into short-chain and more useful hydrocarbons Shorter chain alkanes, alkenes and hydrogen are produced from the cracking of longer chain alkanes Alkenes can be used to make polymers and the hydrogen used to make ammonia Kerosene and diesel oil are often cracked to produce petrol, other alkenes and hydrogen Cracking involves heating the hydrocarbon molecules to around 600 – 700°C to vaporise them The vapours then pass over a hot powdered catalyst of alumina or silica This process breaks covalent bonds in the molecules as they come into contact with the surface of the catalyst, causing thermal decomposition reactions The molecules are broken up in a random way which produces a mixture of smaller alkanes and alkenes Hydrogen and a higher proportion of alkenes are formed at higher temperatures and higher pressure The cracking of decane Page 12 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Decane is catalytically cracked to produce octane for petrol and ethene for ethanol Distinguishing from alkanes The presence of the C=C double bond in an alkene but not an alkane allows us to distinguish between them To do this, bromine water is used Bromine water is an orange coloured solution When bromine water is shaken with an alkane the solution remains orange Page 13 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources When bromine water is shaken with an alkene, the solution will go colourless, as the bromine can add across the double bond meaning it is no longer in solution How to distinguish between alkanes and alkenes Your notes Alkenes will decolourise bromine water Examiner Tips and Tricks When describing what happens to bromine water in an alkene ensure you say colourless, and not clear. Page 14 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Addition Reactions Your notes Addition reactions Extended tier only Alkenes undergo addition reactions in which atoms of a simple molecule add across the C=C double bond In an addition reaction, only one product is formed Alkenes and bromine The reaction between bromine and ethene is an example of an addition reaction The two bromine atoms add across the carbon-carbon double bond to form a saturated compound Bromine water is orange but would decolourise when added to an alkene Bromine atoms add across the C=C in the addition reaction of ethene and bromine Alkenes and hydrogen When alkenes undergo addition reactions with hydrogen, an alkane is formed This reaction requires a nickel catalyst Page 15 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources The reaction between ethene and hydrogen would produce ethane, propene and hydrogen would form propane and so on Your notes The hydrogen adds across the carbon carbon-double bond Alkenes and steam When alkenes undergo addition reactions with steam, an alcohol is formed. Since water is being added to the molecule it is also called a hydration reaction This reaction requires an acid catalyst Ethene would react with steam to produce ethanol, propene will react with steam to produce propanol and so on A water molecule adds across the C=C in the hydration of ethene to produce ethanol Page 16 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Examiner Tips and Tricks You need to be able to draw the structural and displayed formulae of the products of alkenes with steam, hydrogen and bromine. Page 17 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Alcohols Your notes Alcohols All alcohols contain the hydroxyl (-OH) functional group which is the part of alcohol molecules that is responsible for their characteristic reactions Alcohols are a homologous series of compounds that have the general formula CnH2n+1OH They differ by one -CH2 in the molecular formulae from one member to the next Table showing the first three alcohols Name Formula Displayed formula Methanol CH3OH Ethanol C2H5OH Page 18 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Propanol C3H7OH Your notes Ethanol (C2H5OH) is one of the most important alcohols Ethanol can also be represented by its structural formula CH3CH2OH It is the type of alcohol found in alcoholic drinks such as wine and beer It is also used as fuel for cars and as a solvent Ethanol will undergo complete combustion and burn in excess oxygen to produce carbon dioxide and water C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H20 (l) The manufacture of ethanol There are two methods used to manufacture ethanol: The hydration of ethene with steam The fermentation of glucose Both methods have advantages and disadvantages which are considered Hydration of ethene A mixture of ethene and steam is passed over a hot catalyst of phosphoric acid at a temperature of approximately 300 °C The pressure used is 60 atmospheres (6000kPa) The gaseous ethanol is then condensed into a liquid for use Page 19 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes A water molecule adds across the C=C in the hydration of ethene to produce ethanol Fermentation of glucose Sugar or starch is dissolved in water and yeast is added The mixture is then fermented between 25 and 35 °C with the absence of oxygen for a few days Yeast contains enzymes that catalyse the break down of starch or sugar to glucose If the temperature is too low the reaction rate will be too slow and if it is too high the enzymes will become denatured The yeast respire anaerobically using the glucose to form ethanol and carbon dioxide: C6H12O6 → 2CO2 + 2C2H5OH The yeast are killed off once the concentration of alcohol reaches around 15%, so the reaction vessel is emptied and the process is started again Ethanol production by fermentation is therefore a batch process Examiner Tips and Tricks Make sure you learn the conditions for both hydration and fermentation. Comparing methods of ethanol production Page 20 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Extended tier only Hydration of ethene Fermentation Your notes Equipment complex set up required simple equipment needed Raw materials uses non- renewable resources (crude uses renewable resources (sugar cane) oil) Type of continuous process- a steam of batch process- everything is mixed process reactants is constantly passed over a together in a reaction vessel and left for catalyst several days and the process repeated again Rate of fast very slow (several days) reaction Quality of produces pure ethanol produces a dilute solution requiring product further processing Atmospheric no greenhouse gases produced but carbon dioxide produced which is a effects pollutants are formed from the burning of greenhouse gas fossil fuels to maintain high temperatures Reaction high temperatures and pressures low temperatures required conditions required increasing the energy input and cost Page 21 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Carboxylic Acids Your notes Carboxylic acids The carboxylic acids behave like other acids They react with: metals to form a salt and hydrogen carbonates to form a salt, water and carbon dioxide gas bases to form a salt and water The salts formed by the reaction of carboxylic acids all end –anoate So methanoic acid forms a salt called methanoate, ethanoic a salt called ethanoate etc. In the reaction with metals, a metal salt and hydrogen gas are produced Example reactions of carboxylic acids The reaction of ethanoic acid with metals such as magnesium forms the salt magnesium ethanoate and hydrogen gas: 2CH3COOH + Mg → (CH3COO)2Mg + H2 In the reaction with hydroxides, salt and water are formed in a neutralisation reaction For example, the reaction between potassium hydroxide and ethanoic acid forms the salt potassium ethanoate and water: CH3COOH + KOH → CH3COOK + H2O In the reaction with carbonates a metal salt, water and carbon dioxide gas are produced For example, in the reaction between potassium carbonate and ethanoic acid, the salt potassium ethanoate is formed with water and carbon dioxide 2CH3COOH + K2CO3 → 2CH3COOK + H2O + CO2 Examiner Tips and Tricks You need to be able to name and give the formulae of the salts produced in these reactions. Page 22 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Ethanoic Acid & Esterification Reactions Your notes Formation of ethanoic acid Extended tier only Two methods used to make carboxylic acids are: Oxidation by fermentation Using oxidising agents The microbial oxidation (fermentation) of ethanol will produce a weak solution of vinegar (ethanoic acid) This occurs when a bottle of wine is opened as bacteria in the air (acetobacter) will use atmospheric oxygen from air to oxidise the ethanol in the wine C2H5OH (aq) + O2 (g) → CH3COOH (aq)+ H2O (l) The acidic, vinegary taste of wine which has been left open for several days is due to the presence of ethanoic acid Alternatively, oxidising agent potassium manganate(VII) can be used This involves heating ethanol with acidified potassium manganate(VII) in the presence of an acid The heating is performed under reflux which involves heating the reaction mixture in a vessel with a condenser attached to the top The condenser prevents the volatile alcohol from escaping the reaction vessel as alcohols have low boiling points The equation for the reaction is: CH3CH2OH (aq) + 2[O] → CH3COOH (aq) + H2O (l) The solution will change from purple to colourless The oxidising agent is represented by the symbol for oxygen in square brackets Diagram showing the experimental setup for the oxidation with KMnO4 using reflux apparatus Page 23 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Ethanol is heated with acidified potassium manganate(VII) in the presence of an acid Page 24 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Esterification Extended tier only Your notes Alcohols and carboxylic acids react to make esters in esterification reactions Esters are compounds with the functional group R-COO-R Esters are sweet-smelling oily liquids used in food flavourings and perfumes An acid catalyst is required for an esterification reaction Ethanoic acid will react with ethanol in the presence of concentrated sulfuric acid (catalyst) to form ethyl ethanoate: CH3COOH (aq) + C2H5OH (aq) ⇌ CH3COOC2H5 (aq) + H2O (l) Diagram showing the formation of ethyl ethanoate Page 25 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes During this esterification reaction, a molecule of water is also produced Naming Esters An ester is made from an alcohol and carboxylic acid The first part of the name indicates the length of the carbon chain in the alcohol, and it ends with the letters ‘- yl’ Page 26 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources The second part of the name indicates the length of the carbon chain in the carboxylic acid, and it ends with the letters ‘- oate’ Your notes E.g. the ester formed from pentanol and butanoic acid is called pentyl butanoate Diagram showing the origin of each carbon chain in ester; this ester is ethyl butanoate Summary table of some esters and the compounds they are formed from Name of ester Alcohol and carboxylic acid it is formed from propyl methanoate propanol and methanoic acid methyl butanoate methanol and butanoic acid ethyl propanoate ethanol and propanoic acid Page 27 of 27 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers