Separation and purification — Paper 3 · IGCSE Science - Combined 0653

5 (a) Natural gas and petroleum (crude oil) are fossil fuels. (i) Name one other fossil fuel. … [1] (ii) Name the main constituent of natural gas. … [1] (iii) Name the gas in air that reacts with fuels when they burn. … [1] (b) Petroleum is a mixture of hydrocarbons. Fig. 5.1 shows the industrial apparatus used to separate petroleum into useful products. Fig. 5.1 (i) Name the process used to separate petroleum into useful products. … [1] (ii) State the meaning of the term hydrocarbon. … … … [2] (c) Ethanol, C2H5OH, and hydrocarbons burn to form carbon dioxide and one other product during complete combustion. (i) Name the other product. … [1] (ii) Complete the diagram to show the structure of a molecule of ethanol. C O [2]

9 marks

Mark scheme: 5(a)(i) coal ; 1 5(a)(ii) methane ; 1 5(a)(iii) oxygen ; allow O2 ignore O 1 5(b)(i) fractional distillation ; 1 5(b)(ii) compound / molecule of / containing carbon / C and hydrogen / H ; (C and H) only ; 2 5(c)(i) water / H2O ; 1 Question Answer Marks 5(c)(ii) ;; allow (1) if one missing bond or H atom 2

This question in 0653/32 Feb/March 2017

2 (a) A molecule of methane contains one carbon atom bonded to four hydrogen atoms. This bonding, shown in Fig. 2.1, involves shared pairs of electrons. H X X H C H X X H Fig. 2.1 (i) State the type of chemical bonding shown in Fig. 2.1. … [1] (ii) State the type of elements that bond together by sharing pairs of electrons. … [1] (b) (i) During complete combustion, methane forms two gases. Complete the word equation to show this reaction. methane + + [2] (ii) Explain, in terms of energy changes, why methane is used as a fuel. … … [1] (c) Methane is the main constituent of one fossil fuel. (i) State the name of this fossil fuel. … [1] (ii) State the names of two other fossil fuels. … and … [1] (d) Refinery gas, gasoline and diesel oil are separated from a mixture of hydrocarbons by an industrial process. (i) Name this industrial process. … [1] (ii) State one use for bottled refinery gas. … [1]

9 marks

Mark scheme: 2(a)(i) covalent ; 1 2(a)(ii) non-metal(lic) ; 1 2(b)(i) (methane) + oxygen Æ carbon dioxide + water Oxygen on LHS ; RHS any order ; 2 2(b)(ii) releases heat / thermal energy when it reacts / burns / is used ; 1 2(c)(i) natural gas ; 1 2(c)(ii) coal and petroleum (either order) ; 1 2(d)(i) fractional distillation ; 1 Question Answer Marks 2(d)(ii) heating / cooking ; 1

This question in 0653/31 May/June 2017

5 (a) Petroleum is a mixture of hydrocarbons. It is separated into more useful parts using the industrial apparatus shown in Fig. 5.1. Fig. 5.1 (i) Name the process that occurs in this industrial apparatus. … [1] (ii) Suggest why this process involves a physical change and not a chemical change. … … … [1] (iii) Refinery gas is obtained from petroleum. State one use for refinery gas. … [1] (b) The main compound in natural gas has the formula CH4. (i) Name this compound. … [1] (ii) State the total number of atoms and the number of different elements shown in the formula CH4. number of atoms … number of elements … [1] (iii) Complete the diagram to show the structure of one molecule of CH4. C— [1] (c) Petroleum and natural gas are fossil fuels. Name one other fossil fuel. … [1]

7 marks

Mark scheme: 5(a)(i) 1 5(a)(ii) no new substance made / involves only changes of state ; 1 5(a)(iii) cooking / heating allow bottling / bottled gas ; 1 5(b)(i) methane ; 1 5(b)(ii) (atoms) five / 5 and (elements) two / 2 ; 1 5(b)(iii) C atom joined to 4 H atoms by single bonds ; allow correct dot-and-cross diagrams 1 5(c) coal ; 1

This question in 0653/32 May/June 2017

5 (a) Petroleum is a mixture of hydrocarbons. It is separated into more useful parts using the industrial apparatus shown in Fig. 5.1. Fig. 5.1 (i) Name the process that occurs in this industrial apparatus. … [1] (ii) Suggest why this process involves a physical change and not a chemical change. … … … [1] (iii) Refinery gas is obtained from petroleum. State one use for refinery gas. … [1] (b) The main compound in natural gas has the formula CH4. (i) Name this compound. … [1] (ii) State the total number of atoms and the number of different elements shown in the formula CH4. number of atoms … number of elements … [1] (iii) Complete the diagram to show the structure of one molecule of CH4. C— [1] (c) Petroleum and natural gas are fossil fuels. Name one other fossil fuel. … [1]

7 marks

Mark scheme: 5(a)(i) 1 5(a)(ii) no new substance made / involves only changes of state ; 1 5(a)(iii) cooking / heating allow bottling / bottled gas ; 1 5(b)(i) methane ; 1 5(b)(ii) (atoms) five / 5 and (elements) two / 2 ; 1 5(b)(iii) C atom joined to 4 H atoms by single bonds ; allow correct dot-and-cross diagrams 1 5(c) coal ; 1

This question in 0653/33 May/June 2017

8 (a) Water is extracted from a river and then treated to make it suitable for people to use. Two processes, J and chlorination, are used in the purification of the water supply, as shown in Fig. 8.1. river process J chlorination Fig. 8.1 (i) Process J removes insoluble solids from the water. Name process J. … [1] (ii) Explain why chlorine is added to the water supply. … … [1] (iii) Describe a chemical test for chlorine gas. State the positive result of this test. test … result … … [2] (b) Hydrogen chloride is formed when chlorine reacts with hydrogen. (i) Construct the word equation for this reaction. + [1] (ii) State the type of chemical bond that forms between non-metallic elements such as chlorine and hydrogen. Describe how electrons are involved in this bond. bonding type … explanation … … [2] (iii) In a molecule of hydrogen chloride, an atom of hydrogen is bonded to an atom of chlorine. State the formula of hydrogen chloride. … [1] (c) Chlorine is made during the electrolysis of aqueous copper chloride using inert electrodes. (i) Name the electrode at which chlorine forms during this process. … [1] (ii) State the product that forms at the other electrode. … [1] (iii) Identify the electrolyte used in this process. … [1]

11 marks

Mark scheme: 8(a)(i) filtration ; 1 8(a)(ii) kill microbes / sterilise (water) ; 1 8(a)(iii) (damp) litmus (paper) ; turns white / bleached ; 2 8(b)(i) ; LHS either order chlorine + hydrogen Æ hydrogen chloride 1 8(b)(ii) covalent ; share (pair of) electrons ; 2 8(b)(iii) HCl ; 1 8(c)(i) anode ; 1 8(c)(ii) copper ; 1 8(c)(iii) copper chloride solution / aqueous copper chloride ; 1

This question in 0653/33 May/June 2017

5 (a) Pure water can be separated from sea water using the apparatus shown in Fig. 5.1. water out condenser cold water in sea water pure water heat Fig. 5.1 (i) Name this process. … [1] (ii) Describe the change in the temperature of the pure water as it passes through the condenser. … [1] (b) The purification of a water supply involves filtration and chlorination. Explain how filtration and chlorination purify the water supply. filtration … … chlorination … … [2] (c) Petroleum is separated into different fractions, as shown in Fig. 5.2. refinery gas gasoline gas oil hot petroleum Fig. 5.2 (i) State one use for refinery gas and one use for gas oil. refinery gas … gas oil … [2] (ii) Gasoline is a mixture of hydrocarbons. Explain what is meant by a hydrocarbon. … … [2] (d) The structures of six compounds are shown in Fig. 5.3. H H H O C O H C H H C C H H H H A B C H H H H C C H C C OH O H H H H H H D E F Fig. 5.3 (i) Using letters A to F, identify the two products of the complete combustion of hydrocarbons. … and … [1] (ii) Using letters A to F, identify the main constituent of natural gas. … [1]

10 marks

Mark scheme: 5(a)(i) distillation ; 1 5(a)(ii) decrease ; 1 5(b) (filtration) remove (named) solids ; (chlorination) kill microbes / bacteria / sterilizes ; 2 5(c)(i) (refinery gas) bottled gas / heating / cooking ; (gas oil) diesel fuel / diesel engines / diesel vehicles ; 2 5(c)(ii) compound / molecule containing hydrogen and carbon ; only (C and H); 2 5(d)(i) A F ; 1 5(d)(ii) B ; 1

This question in 0653/33 Oct/Nov 2017

2 (a) A student investigates the reactivity of four different metals. She places pieces of calcium, copper, iron and zinc separately in dilute hydrochloric acid, as shown in Fig. 2.1. metal dilute hydrochloric acid Fig. 2.1 (i) Place these four metals in order of reactivity, from most to least reactive. … most reactive … … … least reactive [2] (ii) Suggest what happens to the pH number of the acid when it reacts with a piece of metal. … [1] (b) Excess magnesium powder reacts with dilute hydrochloric acid. During this reaction, a gas and aqueous magnesium chloride solution are produced. (i) Name this gas. … [1] (ii) State how the unreacted solid magnesium can be removed from the reaction mixture. … [1] (iii) State how solid magnesium chloride can be obtained from magnesium chloride solution. … [1] (c) An atom of an isotope of magnesium is represented by: 2512Mg (i) State the atomic number and the mass number of this atom. atomic number … mass number … [1] (ii) State the number of neutrons in this atom. … [1] (d) Aluminium is used in overhead power cables. Aluminium alloys are used in aircraft bodies. (i) State the physical property of aluminium that makes it suitable for use in power cables. … [1] (ii) Explain why aluminium alloys, rather than pure aluminium, are used in aircraft bodies. … [1]

10 marks

Mark scheme: 2(a)(i) calcium Ca zinc / Zn iron / Fe copper / Cu ;; 1 mark for calcium first and copper last 2 marks for all four correct 2 2(a)(ii) increases / goes up / gets (closer) to 7 ; 1 2(b)(i) hydrogen ; 1 2(b)(ii) filter / filtering / filtration ; 1 2(b)(iii) crystallisation / evaporation / heat ; 1 2(c)(i) (atomic no.) 12 and (mass no.) 25 ; 1 2(c)(ii) 13 ; 1 2(d)(i) (electrical) conductor ; 1 2(d)(ii) higher strength ; 1

This question in 0653/31 May/June 2018

5 (a) The process used to produce refinery gas, gasoline and gas oil from petroleum is shown in Fig. 5.1. refinery gas gasoline gas oil petroleum Fig. 5.1 (i) Name this process. … [1] (ii) The petroleum is changed in this process. No new chemicals are made. Name this type of change. … [1] (iii) Petroleum is a mixture of different compounds. State what is meant by the terms mixture and compound. mixture … … … compound … … … [2] (b) Refinery gas contains ethane, C2H6, a hydrocarbon. (i) A molecule of ethane contains covalent bonds. Explain how covalent bonds form between non‑metallic elements. Use ideas about electrons in your answer. … … [1] (ii) When ethane burns, water is formed. Describe a chemical test and the positive result for water. test … result … [2] (iii) When ethane burns, there is a temperature increase. Identify the type of chemical reaction that produces a temperature increase. … [1]

8 marks

Mark scheme: 5(a)(i) fractional distillation ; 1 5(a)(ii) physical ; 1 5(a)(iii) mixture idea that the components are not joined / bonded (together) / idea that the components retain their original properties / components can be separated by physical processes ; compound different atoms / elements bonded / joined (together) / has different properties from the elements / elements cannot be separated by physical processes ; 2 5(b)(i) shared (pair of) electrons) ; 1 5(b)(ii) test white / anhydrous copper sulfate ; result (turns) blue ; or blue / anhydrous cobalt chloride (paper); result (turns) pink; 2 5(b)(iii) exothermic ; 1

This question in 0653/31 May/June 2018

5 (a) A student makes magnesium sulfate by reacting magnesium with a dilute acid. (i) Name the acid. … [1] (ii) Describe the pH change of the mixture during the reaction. … [1] (iii) Name one other substance that reacts with this acid to make magnesium sulfate. … [1] (iv) The reaction between magnesium and this acid is exothermic. State what is meant by the term exothermic. … … [1] (b) Another student reacts calcium with excess dilute acid in a beaker. Calcium sulfate forms as a solid in the beaker. Suggest the separation method that is used to separate the solid calcium sulfate from the excess acid. Explain how this separation method removes the solid from the liquid. method … explanation … … … [2] (c) Calcium is in Group II of the Periodic Table. (i) Complete the following sentences using words from the list. Each word may be used once, more than once or not at all. good high low poor Calcium is a … electrical conductor. Calcium has a … melting point. [1] (ii) State the order of reactivity of calcium, magnesium and sodium. … most reactive … … least reactive [1]

8 marks

Mark scheme: 5(a)(i) sulfuric (acid) ; 1 5(a)(ii) increases ; 1 5(a)(iii) magnesium oxide / magnesium hydroxide / magnesium carbonate; 1 5(a)(iv) temperature increases / release of heat (thermal energy) ; 1 5(b) (method) filter / filtering / filtration ; (explanation) solid (particles) stays on filter paper / cannot pass through filter paper / liquid (particles) can ; 2 5(c)(i) good and high 1 5(c)(ii) (most reactive) sodium / Na calcium / Ca (least reactive) magnesium / Mg ; 1

This question in 0653/31 Oct/Nov 2018

8 Petroleum is separated into more useful substances using the process shown in Fig. 8.1. refinery gas gasoline gas oil petroleum Fig. 8.1 (a) (i) Name this process. … [1] (ii) State one use for gas oil. … [1] (b) During the complete combustion of gasoline, the amounts of some gases in the air change. Name two of these gases and describe the change in the amount of each. gas 1 name … change … gas 2 name … change … [4] (c) The formula of ethanol is C2H5OH. Complete the structure of a molecule of ethanol. Show all of the bonds between the atoms. C C [2]

8 marks

Mark scheme: 8(a)(i) fractional distillation ; 1 8(a)(ii) fuel (in diesel engines) ; 1 8(b) any two gases of: name oxygen ; change decrease ; or name carbon dioxide ; change increase ; or name water (vapour) ; change increase ; 2nd mark dependent on correct gas named Max 4 4 8(c) correct arrangement of atoms ; all (single) bonds shown correctly ; 2

This question in 0653/31 Oct/Nov 2018

2 (a) The Periodic Table contains the symbols of all of the elements. Complete the sentences about the Periodic Table. The Periodic Table lists the elements in order of their … number. The unreactive gases in Group VIII, which include helium, neon and argon, are known as the … gases. The collection of metals in the middle of the Periodic Table have high densities and form coloured compounds. They are known as the … elements. [3] (b) Carbon dioxide is a compound of carbon and oxygen, two non-metallic elements. (i) State the name of the type of bonding between a carbon atom and an oxygen atom. … [1] (ii) Describe, in terms of electrons, the bonding between a carbon atom and an oxygen atom. … … [1] (c) The compound sodium chloride contains sodium ions and chloride ions. Describe, in terms of electrons, the formation of ions from atoms. … … [1] (d) A mixture contains aqueous sodium chloride and insoluble powdered charcoal (carbon). (i) Suggest how the powdered charcoal can be separated from the mixture. … … [1] (ii) Suggest how water can be removed from aqueous sodium chloride. … … [1] (iii) State whether the separation of this mixture into charcoal, water and sodium chloride is a physical change or a chemical change. Explain your answer. change … explanation … … [1]

9 marks

Mark scheme: 2(a) atomic / proton ; noble ; transition ; 3 2(b)(i) covalent ; 1 2(b)(ii) (electrons are) shared ; 1 2(c) (electrons are) lost / gained / lost and gained ; 1 Question Answer Marks 2(d)(i) filter / filtering / filtration ; 1 2(d)(ii) evaporation ; 1 2(d)(iii) physical and no new substance(s) is / are made ; 1

This question in 0653/33 Oct/Nov 2018

5 (a) Petroleum contains hydrocarbons. These are separated into useful fractions by fractional distillation, as shown in Fig. 5.1. refinery gas gasoline naphtha gas oil petroleum bitumen Fig. 5.1 (i) Identify a fraction shown in Fig. 5.1 used for fuel in cars. … [1] (ii) Identify a fraction shown in Fig. 5.1 used for bottled gas for heating and cooking. … [1] (b) (i) Name the type of hydrocarbon which contains only single bonds. … [1] (ii) Identify the products of the complete combustion of hydrocarbons. … and … [1] (c) Compound X is made from large hydrocarbon molecules in a reaction called cracking. Compound X reacts with aqueous bromine, changing it from orange to colourless. Molecules of compound X join together to form a polymer. (i) Suggest the identity of compound X. … [1] (ii) State the type of polymerisation in which molecules of compound X form a polymer. … [1] (d) Hydrocarbon molecules contain atoms of the elements carbon and hydrogen only. (i) A carbon atom has 6 electrons. Complete Fig. 5.2 to show the electronic structure of this carbon atom. Fig. 5.2 [1] (ii) Complete the dot-and-cross diagram in Fig. 5.3 to show the covalent bond in a molecule of hydrogen gas, H2. H H Fig. 5.3 [1] (iii) State why covalent bonds, rather than ionic bonds, form between carbon atoms and hydrogen atoms. … … [1] [Total: 9]

9 marks

Mark scheme: 5(a)(i) gasoline ; 1 5(a)(ii) refinery gas ; 1 5(b)(i) alkane(s) / saturated ; 1 5(b)(ii) carbon dioxide / CO2 and water / H2O ; 1 5(c)(i) ethene / C2H4 / any named alkene / any correct alkene formula / alkene ; 1 5(c)(ii) addition (polymerisation) ; 1 5(d)(i) 2,4 arrangement ; 1 Question Answer Marks 5(d)(ii) H H 1 5(d)(iii) they / carbon and hydrogen are (both) non-metals / it is a simple molecule ; 1 X •

This question in 0653/32 May/June 2019

8 (a) The hydrocarbons in petroleum are separated into useful products using the process shown in Fig. 8.1. refinery gas gasoline naphtha gas oil petroleum bitumen Fig. 8.1 (i) Name this process. … [1] (ii) State what is meant by hydrocarbon. … … [2] (iii) State one use for naphtha. … [1] (b) When hydrocarbons burn, they may produce carbon dioxide, carbon monoxide and water. (i) Describe one test to show the presence of water. State the positive result. test … result … [2] (ii) Describe one adverse effect of carbon monoxide on humans. … … [1] (iii) Suggest the percentage of carbon dioxide in clean air. percentage = … % [1] (iv) Using your knowledge of the amounts of other gases in clean air, explain your answer to (iii). … … [1] [Total: 9]

9 marks

Mark scheme: 8(a)(i) fractional distillation ; 1 8(a)(ii) compound/molecule that contains carbon and hydrogen ; only ; 2 8(a)(iii) (raw material) to make chemicals ; 1 8(b)(i) (test) copper((II)) sulfate or cobalt((II)) chloride ; (result) (white) turns blue (blue) turns pink ; 2 8(b)(ii) toxic / poisonous (to humans/animals) / breathing difficulties / combines with haemoglobin in place of oxygen / reduces oxygen carrying capacity of the blood ; 1 8(b)(iii) (percentage) ≤ 1(%) ; 1 8(b)(iv) nitrogen = 78% and oxygen = 21% or nitrogen + oxygen = 99% ; 1

This question in 0653/31 Oct/Nov 2019

8 Sodium chloride, NaCl, is an ionic compound. (a) Name one method of obtaining solid sodium chloride from aqueous sodium chloride. … [1] (b) The electronic structures of an atom of sodium, Na, and of an atom of chlorine, Cl, are shown in Fig. 8.1. Na Cl atom atom Fig. 8.1 Complete Fig. 8.2 to show the electronic structure of a sodium ion, Na+, and of a chloride ion, Cl –. Na+ Cl – ion ion Fig. 8.2 [2] (c) Concentrated aqueous sodium chloride is electrolysed using inert electrodes, as shown in Fig. 8.3. low voltage d.c. supply – + concentrated aqueous sodium chloride Fig. 8.3 Complete the word equation for the electrolysis of concentrated aqueous sodium chloride. concentrated aqueous sodium + + sodium hydroxide chloride [2] (d) Suggest the pH of aqueous sodium hydroxide and its effect on the colour of Universal Indicator. pH … colour … [2] (e) State the effect of chlorine gas on damp litmus paper. … [1] [Total: 8]

8 marks

Mark scheme: 8(a) evaporate ; allow distil / crystallise / boil 1 8(b) drawn: Na+ 2, 8 ; Cl– 2, 8, 8 ; 2 8(c) (either order) concentrated aqueous sodium chloride  sodium hydroxide + hydrogen ; + chlorine ; 2 8(d) pH > 7 to 14 ; colour blue-green / blue / purple ; 2 8(e) (blue / purple to) white / bleached ; 1

This question in 0653/32 Feb/March 2020

5 (a) Petroleum is separated using the process shown in Fig. 5.1. refinery gas gasoline gas oil petroleum Fig. 5.1 (i) Name the process shown in Fig. 5.1. … [1] (ii) Refinery gas and gas oil can be used as fuels. State one use for each of these fuels. refinery gas … gas oil … [2] (iii) Identify the greenhouse gas that forms during the complete combustion of gasoline. … [1] (b) Petroleum is a mixture of hydrocarbon molecules called alkanes. (i) Explain what is meant by hydrocarbon. … … [2] (ii) State the name of a process used to produce alkenes. … [1] (iii) Describe the difference between the bonding in alkanes and in alkenes. … … [1] (iv) Many ethene molecules combine to form poly(ethene). State the type of addition reaction that occurs. … [1] [Total: 9]

9 marks

Mark scheme: 5(a)(i) fractional distillation ; 1 5(a)(ii) (refinery gas) bottled gas / heating / cooking ; (gas oil) diesel (engines / fuel) ; 2 5(a)(iii) carbon dioxide / CO2 ; 1 Question Answer Marks 5(b)(i) (molecules / compounds) contain carbon and hydrogen (atoms) ; only ; 2 5(b)(ii) cracking ; 1 5(b)(iii) alkanes contain only single (bonds) / alkenes contain double (bonds) ; 1 5(b)(iv) (addition) polymerisation ; 1

This question in 0653/31 May/June 2020

8 (a) Copper chloride is made in the reaction between excess solid copper carbonate and dilute hydrochloric acid. The word equation for this reaction is shown. copper hydrochloric copper carbon + + + water carbonate acid chloride dioxide (i) Describe how unreacted copper carbonate is removed from the mixture when the reaction is complete. … [1] (ii) Suggest how solid copper chloride is obtained from the aqueous copper chloride that forms. … [1] (iii) State the test for carbon dioxide and the positive test result. test … result … [2] (b) Chlorine is produced when electricity is passed through concentrated aqueous sodium chloride, as shown in Fig. 8.1. low voltage d.c. supply negative positive electrode electrode concentrated aqueous sodium chloride Fig. 8.1 (i) Name this process. … [1] (ii) Identify the solvent and the solute through which electricity is passed during this process. solvent … solute … [1] (iii) Identify one element in the same group of the Periodic Table as chlorine that has a higher melting point than chlorine. … [1] [Total: 7]

7 marks

Mark scheme: 8(a)(i) filter / filtration ; 1 8(a)(ii) crystallize / evaporate (the water) ; 1 8(a)(iii) (test) limewater ; (result) (turns) cloudy / milky / chalky ; 2 8(b)(i) electrolysis ; 1 8(b)(ii) (solvent) water / H2O AND (solute) sodium chloride / NaCl BOTH required for one mark ; 1 8(b)(iii) bromine / Br2 or iodine / I2 ; allow astatine 1

This question in 0653/32 May/June 2020

8 (a) Methane, CH4, is an alkane. (i) Methane is the main constituent of a fossil fuel. Name this fossil fuel. … [1] (ii) Name the type of chemical bonds in a molecule of methane. … [1] (iii) Fig. 8.1 is an incomplete dot-and-cross diagram of a molecule of methane. On Fig. 8.1, draw dots and crosses to show all of the outer shell electrons in a molecule of methane. H H C H H Fig. 8.1 [2] (b) A sample of refinery gas contains only alkane molecules. (i) Name the process used to obtain refinery gas from petroleum. … [1] (ii) Describe the effect, if any, of this sample of refinery gas on aqueous bromine. … [1] (c) Fossil fuels are used for heating. (i) State the type of chemical reaction that produces a temperature increase during the combustion of fossil fuels. … [1] (ii) Suggest the effect of the combustion of methane on the number of nitrogen molecules and on the number of oxygen molecules in a limited supply of air. nitrogen molecules … oxygen molecules … [2] (iii) During the combustion of fossil fuels, carbon dioxide is produced. State the test and the positive result for carbon dioxide. test … result … [2] [Total: 11]

11 marks

Mark scheme: 8(a)(i) natural gas ; 1 8(a)(ii) covalent ; 1 8(a)(iii) one bond shown correctly ; four bonds shown correctly ; 2 8(b)(i) fractional distillation ; 1 8(b)(ii) none / no effect / (stays) orange-brown ; 1 8(c)(i) exothermic ; 1 8(c)(ii) (nitrogen) no change / no effect / none ; (oxygen) decreases ; 2 8(c)(iii) (test) limewater ; (result) turns milky ; 2

This question in 0653/32 Oct/Nov 2020

2 Natural gas and petroleum are two types of fossil fuel. (a) Name one other fossil fuel. … [1] (b) State the main constituent of natural gas. … [1] (c) Petroleum is separated by the process shown in Fig. 2.1. refinery gas gasoline naphtha gas oil petroleum bitumen Fig. 2.1 (i) Name this process. … [1] (ii) State one use for bitumen. … [1] (d) Ethane and ethene are both hydrocarbons. Ethane is an alkane. Ethene is an alkene. (i) Two compounds are made during the complete combustion of ethane and of ethene. Water is one of these compounds. Identify the other compound. … [1] (ii) Describe one difference between molecules of ethane and molecules of ethene. … … [1] (e) The structure of a molecule of another hydrocarbon is shown in Fig. 2.2. H H H H C C C H H H H Fig. 2.2 Deduce the formula of this hydrocarbon. … [1] [Total: 7]

7 marks

Mark scheme: 2(a) coal ; 1 2(b) methane / CH4 ; 1 2(c)(i) fractional distillation ; 1 2(c)(ii) (for making) roads ; 1 2(d)(i) carbon dioxide / CO2 ; 1 2(d)(ii) ethene, is unsaturated / contains double bonds ; 1 2(e) C3H8 ; 1

This question in 0653/32 Feb/March 2021

5 (a) Petroleum is a mixture of hydrocarbons. Useful products are obtained by process X and process Y, as shown in Fig. 5.1. process X process Y gasoline naphthanaphtha alkenes strong heat petroleum Fig. 5.1 (i) Process X separates gasoline and naphtha from petroleum. Name process X. … [1] (ii) Process Y produces alkenes. Name process Y. … [1] (iii) State whether process Y is a chemical change or a physical change. Explain your answer. change … explanation … … [1] (iv) Describe a chemical test for alkenes, and state the observation for a positive result. test … result … [2] (b) The structure of a molecule of propene, an alkene, is shown in Fig. 5.2. H H H H C C C H H Fig. 5.2 Water is formed during the complete combustion of propene. (i) Identify the other substance that is formed during this combustion. … [1] (ii) Name the gas in air that reacts with propene during combustion, and state the percentage of this gas in clean air. gas … percentage … [1] (iii) Use Fig. 5.2 to deduce the formula of propene. … [1] [Total: 8]

8 marks

Mark scheme: 5(a)(i) fractional distillation ; 1 5(a)(ii) cracking ; 1 5(a)(iii) change: chemical AND explanation: new substances are made / bonds are broken / new bonds are formed ; 1 5(a)(iv) test: (add aqueous) bromine ; result: (orange to) colourless / decolourises ; 2 5(b)(i) carbon dioxide / CO2 ; 1 5(b)(ii) gas: oxygen AND percentage: 21(%) ; 1 5(b)(iii) C3H6 ; 1

This question in 0653/31 May/June 2021

2 (a) A mixture contains water, dissolved sodium chloride and an insoluble solid compound. (i) State what is meant by insoluble and compound. insoluble … … compound … … [2] (ii) Describe how crystals of sodium chloride are obtained from this mixture. … … … … … [3] (b) Water is a covalent molecule. Complete Fig. 2.1 to show the dot-and-cross diagram of a molecule of water. Show all the outer shell electrons. H O H Fig. 2.1 [2] (c) An atom of oxygen contains 8 electrons and it has the nucleon number (mass number) 16. State what is meant by nucleon number. … … [1] (d) Complete Table 2.1 to show the charges and approximate relative masses of neutrons and protons. Table 2.1 particle charge relative mass neutron proton [2] [Total: 10]

10 marks

Mark scheme: 2(a)(i) insoluble: cannot / does not, dissolve (in water) ; compound: two (or more) elements (chemically) combined ; 2 Question Answer Marks 2(a)(ii) any three from: filter (at the start) / filter (off the insoluble solid) ; evaporate / heat (the NaCl solution) ; leave to (cool and) crystallise ; filter off the crystals / dry between folds of filter paper ; 3 2(b) two bond pairs ; two lone pairs on O ; 2 2(c) (the total number of) protons and neutrons (in the nucleus of an atom) ; 1 2(d) particle charge relative mass neutron 0 1 proton +1 1 ;; neutron row correct ; proton row correct ; 2

This question in 0653/32 May/June 2021

2 (a) Fig. 2.1 shows a process used to separate substances in a fossil fuel. fossil fuel Fig. 2.1 (i) Name this process. … [1] (ii) Name the fossil fuel that is separated by this process. … [1] (b) Methane is the main constituent of another fossil fuel. (i) Name this fossil fuel. … [1] (ii) Complete Fig. 2.2 to show the dot-and-cross diagram of one molecule of methane, CH4. H H C H H Fig. 2.2 [2] (iii) Identify a greenhouse gas that is formed by the complete combustion of methane. … [1] (c) Carbon has atomic number 6 and mass number 12. Hydrogen has atomic number 1 and mass number 1. Complete Table 2.1 to show the number of protons and the number of neutrons in one atom of carbon and in one atom of hydrogen. Table 2.1 atom number of protons number of neutrons carbon hydrogen [2] [Total: 8]

8 marks

Mark scheme: 2(a)(i) fractional distillation ; 1 2(a)(ii) petroleum ; 1 2(b)(i) natural gas ; 1 2(b)(ii) ;; four bonding pairs of electrons = 2 marks one bonding pair correct = 1 mark 2 2(b)(iii) carbon dioxide / CO2 ; 1 Question Answer Marks 2(c) number of protons number of neturons carbon 6 6 hydrogen 1 0 carbon row correct ; hydrogen row correct ; 2

This question in 0653/33 May/June 2021

5 (a) The boxes on the left of Fig. 5.1 show some separation and collection methods. The boxes on the right of Fig. 5.1 show some substances and the mixtures they come from. Complete Fig. 5.1 to show the method used to separate and collect each substance from its mixture. Draw one line from each box on the left to one box on the right. Distillation of water from salty water has been done as an example for you. method substance and its mixture dyes chromatography ink insoluble copper oxide crystallisation aqueous copper sulfate naphtha distillation petroleum salt filtration salty water water fractional distillation salty water Fig. 5.1 [2] (b) Evaporation is also used to separate some mixtures. During evaporation, a liquid becomes a gas. (i) Explain why evaporation is a physical change and not a chemical change. … … [1] (ii) Describe how the structure of a gas is different to the structure of a liquid in terms of particle arrangement and particle motion. particle arrangement … … particle motion … … [2] (c) Copper sulfate and water are made when copper oxide reacts with an acid. State the name of this acid. … [1] (d) State one use for naphtha. … [1] [Total: 7]

7 marks

Mark scheme: 5(a) two correct ; all correct ; 2 5(b)(i) only a state change / no new substance made ; 1 5(b)(ii) particles in a gas are: ORA far apart / (more) spread out ; move more freely ; 2 5(c) sulfuric (acid) ; 1 5(d) (as a) feedstock / for making chemicals ; 1

This question in 0653/31 Oct/Nov 2021

2 (a) A student separates some insoluble solid material from concentrated aqueous sodium chloride. (i) State the name of the separation method that the student uses. … [1] (ii) Identify the solute and the solvent in concentrated aqueous sodium chloride. solute … solvent … [1] (iii) State what is meant by concentrated. Use ideas about particles in your answer. … … [1] (b) The student passes an electric current through concentrated aqueous sodium chloride, as shown in Fig. 2.1. low voltage d.c. supply – + inert carbon electrodes concentrated aqueous sodium chloride Fig. 2.1 (i) State the name of this process. … [1] (ii) State the name of the positive electrode. … [1] (iii) Identify the product that forms at the negative electrode. … [1] (c) Sodium is a metal, and chlorine is a diatomic non-metal. When sodium and chlorine are heated together, sodium chloride is formed. (i) State what is meant by diatomic. … … [1] (ii) State the type of chemical bonding present in sodium chloride. … [1] (iii) Describe a chemical test for the presence of chloride ions in aqueous sodium chloride. State the observation for a positive result. test … … observation … … [2] [Total: 10]

10 marks

Mark scheme: 2(a)(i) filtration / filter(ing) ; 1 2(a)(ii) solute: sodium chloride / NaCl AND solvent: water / H2O ; 1 2(a)(iii) there are many / more solute particles in (a solution) ; 1 2(b)(i) electrolysis ; 1 2(b)(ii) anode ; 1 2(b)(iii) hydrogen ; 1 2(c)(i) (contains) only two atoms joined (in a molecule) ; 1 2(c)(ii) ionic ; 1 2(c)(iii) test: (aqueous) silver nitrate AND (dilute) nitric acid ; result: white precipitate ; 2

This question in 0653/32 Oct/Nov 2021

2 (a) A student separates some insoluble solid material from concentrated aqueous sodium chloride. (i) State the name of the separation method that the student uses. … [1] (ii) Identify the solute and the solvent in concentrated aqueous sodium chloride. solute … solvent … [1] (iii) State what is meant by concentrated. Use ideas about particles in your answer. … … [1] (b) The student passes an electric current through concentrated aqueous sodium chloride, as shown in Fig. 2.1. low voltage d.c. supply – + inert carbon electrodes concentrated aqueous sodium chloride Fig. 2.1 (i) State the name of this process. … [1] (ii) State the name of the positive electrode. … [1] (iii) Identify the product that forms at the negative electrode. … [1] (c) Sodium is a metal, and chlorine is a diatomic non-metal. When sodium and chlorine are heated together, sodium chloride is formed. (i) State what is meant by diatomic. … … [1] (ii) State the type of chemical bonding present in sodium chloride. … [1] (iii) Describe a chemical test for the presence of chloride ions in aqueous sodium chloride. State the observation for a positive result. test … … observation … … [2] [Total: 10]

10 marks

Mark scheme: 2(a)(i) filtration / filter(ing) ; 1 2(a)(ii) solute: sodium chloride / NaCl AND solvent: water / H2O ; 1 2(a)(iii) there are many / more solute particles in (a solution) ; 1 2(b)(i) electrolysis ; 1 2(b)(ii) anode ; 1 2(b)(iii) hydrogen ; 1 2(c)(i) (contains) only two atoms joined (in a molecule) ; 1 2(c)(ii) ionic ; 1 2(c)(iii) test: (aqueous) silver nitrate AND (dilute) nitric acid ; result: white precipitate ; 2

This question in 0653/33 Oct/Nov 2021

2 (a) An aqueous solution of salt MX is made by dissolving solid MX in water. (i) Identify the solvent and the solute in aqueous MX. solute … solvent … [2] (ii) A student tests separate samples of aqueous MX. The results are shown in Table 2.1. Complete Table 2.1 by naming the ions that these tests show are in aqueous MX. Table 2.1 test result name of ion add aqueous sodium green precipitate, insoluble in hydroxide excess add aqueous barium white precipitate ions under acidic conditions [2] (b) A student makes an aqueous solution of MX by reacting excess metal M with dilute acid HX. The student then separates the excess, unreacted solid metal M from the reaction mixture. (i) Suggest how the student separates solid metal M from the reaction mixture. … [1] (ii) State whether this separation process is a chemical change or a physical change. Explain your answer. change … explanation … … [1] (iii) State the effect of increasing the temperature on the rate of this reaction. … … [1] (iv) During the reaction between metal M and dilute acid HX, atoms of M become cations. Explain how atoms become cations. … … [1] (v) Suggest what happens to the value of the pH of the reaction mixture during the reaction between excess metal M and dilute acid HX. … … [1] [Total: 9]

9 marks

Mark scheme: 2(a)(i) (solute) MX ; (solvent) water / H2O ; 2 2(a)(ii) ;; 2 2(b)(i) filter / filtration ; 1 2(b)(ii) (change) physical AND (explanation) no new substance is made ; 1 2(b)(iii) (rate) increases ; 1 2(b)(iv) (atoms) lose electron(s) ; 1 2(b)(v) pH increases ; 1

This question in 0653/31 May/June 2022

2 A student measures the melting point of some salty water and some pure water. The results are shown in Table 2.1. Table 2.1 melting point / °C salty water –5 pure water 0 (a) (i) State the name of one piece of apparatus that is used to measure temperature. … [1] (ii) State whether melting is a chemical change or a physical change. Give a reason for your answer. change … reason … … [1] (iii) The student also measures the boiling point of the two liquids. State whether melting and boiling are endothermic or exothermic changes. melting … boiling … [1] (b) Salty water contains salt dissolved in water. State the method used to obtain pure water from salty water. Explain your answer. method … explanation … … … [2] (c) Pure water exists as a solid, as a liquid or as water vapour (a gas). Complete Table 2.2 to describe the structure of solid water, liquid water and water vapour. Table 2.2 particle particle particle separation arrangement motion solid water close together liquid water moving around water vapour random [3] (d) (i) Salt is a compound that is formed when atoms of sodium lose electrons and atoms of chlorine gain electrons. State the name of the type of chemical bonding in sodium chloride. … [1] (ii) Water is a compound that is formed when hydrogen and oxygen, both non-metals, share electrons. State the type of chemical bonding in water. … [1] [Total: 10]

10 marks

Mark scheme: 2(a)(i) thermometer ; 1 2(a)(ii) (change) physical AND (reason) no new substance is made ; 1 2(a)(iii) (melting) endothermic AND (boiling) endothermic ; 1 2(b) (method) distillation ; (explanation) water evaporates and leaves the salt behind ; 2 Question Answer Marks 2(c) particle arrangement particle separation particle motion solid water regular / ordered close together vibrate / move about a fixed point liquid water random close together moving around water vapour random far apart / spread out moving rapidly ;;; 6 correct = 3 marks 3 – 5 correct = 2 marks 1 – 2 correct = 1 mark 3 2(d)(i) ionic ; 1 2(d)(ii) covalent ; 1

This question in 0653/31 May/June 2023

5 Natural gas and petroleum are fossil fuels. (a) Methane is the main constituent of natural gas. Complete the word equation for the complete combustion of methane. methane + + [1] (b) Petroleum is a mixture of saturated hydrocarbon molecules. It is separated by the process shown in Fig. 5.1. fractions petroleum Fig. 5.1 (i) State the name of this process. … [1] (ii) State the name of the fraction used for bottled gas for heating and cooking. … [1] (c) Naphtha from petroleum is used to produce alkenes. (i) State the name of the process that is used to produce alkenes. … [1] (ii) Describe the colour change when aqueous bromine is added to an alkene. from … to … [1] (iii) Alkenes form addition polymers. Name one alkene and the addition polymer that it forms. alkene … addition polymer … [1] [Total: 6]

6 marks

Mark scheme: 5(a) 1 all correct ; 5(b)(i) fractional distillation ; 1 5(b)(ii) refinery gas ; 1 5(c)(i) cracking ; 1 5(c)(ii) orange / brown (to) colourless ; 1 5(c)(iii) any named alkene AND its addition polymer, e.g., ethene AND poly(ethene) ; 1

This question in 0653/32 Oct/Nov 2023

5 Natural gas and petroleum are fossil fuels. (a) Methane is the main constituent of natural gas. Complete the word equation for the complete combustion of methane. methane + + [1] (b) Petroleum is a mixture of saturated hydrocarbon molecules. It is separated by the process shown in Fig. 5.1. fractions petroleum Fig. 5.1 (i) State the name of this process. … [1] (ii) State the name of the fraction used for bottled gas for heating and cooking. … [1] (c) Naphtha from petroleum is used to produce alkenes. (i) State the name of the process that is used to produce alkenes. … [1] (ii) Describe the colour change when aqueous bromine is added to an alkene. from … to … [1] (iii) Alkenes form addition polymers. Name one alkene and the addition polymer that it forms. alkene … addition polymer … [1] [Total: 6]

6 marks

Mark scheme: 5(a) 1 all correct ; 5(b)(i) fractional distillation ; 1 5(b)(ii) refinery gas ; 1 5(c)(i) cracking ; 1 5(c)(ii) orange / brown (to) colourless ; 1 5(c)(iii) any named alkene AND its addition polymer, e.g., ethene AND poly(ethene) ; 1

This question in 0653/33 Oct/Nov 2023

5 Petroleum is a mixture of hydrocarbons. Fig. 5.1 shows the process that separates petroleum into hydrocarbons and another process, process B. refinery gas process B ethene strong heat petroleum fraction A Fig. 5.1 (a) (i) Circle the name of the process that separates petroleum into hydrocarbons. chromatography crystallisation filtration fractional distillation [1] (ii) State one use for refinery gas. … [1] (iii) State one use for fraction A. … [1] (b) Process B produces the unsaturated hydrocarbon ethene. (i) State the name of process B. … [1] (ii) Explain why ethene is described as unsaturated and as a hydrocarbon. unsaturated … … hydrocarbon … … [2] (iii) Describe a chemical test for unsaturated hydrocarbons. State the observation for a positive result. test … observation … … [2] (iv) State the type of chemical reaction that converts ethene monomer units to poly(ethene). … [1] (c) Petroleum is one example of a fossil fuel. Another fossil fuel has a greenhouse gas as its main constituent. State the name of this other fossil fuel. … [1] [Total: 10]

10 marks

Mark scheme: 5(a)(i) fractional distillation (circled) ; 1 5(a)(ii) heating / cooking ; 1 5(a)(iii) road surfaces ; 1 5(b)(i) cracking ; 1 5(b)(ii) (unsaturated) contains a (C=C) double bond ; (hydrocarbon) contains hydrogen and carbon only ; 2 5(b)(iii) (test) (aqueous) bromine ; (observation) decolourises / turns (from orange to) colourless ; 2 5(b)(iv) addition polymerisation ; 1 5(c) natural gas ; 1

This question in 0653/31 May/June 2024

8 The structures of compounds P and Q are shown in Fig. 8.1. H H H H H H H C C C H H C C C H H H H H P Q Fig. 8.1 (a) (i) The formula for compound P is C3H8 . Deduce the formula of compound Q. … [1] (ii) The combustion of compound P is an exothermic reaction. Describe the meaning of exothermic. … … [1] (iii) Complete the word equation for the complete combustion of compound P. compound P + + [2] (b) Describe the effect, if any, of compounds P and Q on the colour of aqueous bromine. P … Q … [2] (c) Compound P is in refinery gas. Refinery gas is obtained from petroleum using a separation process. (i) State the name of the separation process used to obtain refinery gas from petroleum. … [1] (ii) During this separation process, some hydrocarbons change state from a liquid to a gas. State if this change is a chemical change or a physical change. Explain your answer. type of change … explanation … … [1] (iii) State one use for refinery gas. … [1] (d) Petroleum is one example of a fossil fuel. State the name of two other fossil fuels. 1 … 2 … [2] [Total: 11]

11 marks

Mark scheme: 8(a)(i) C3H6 ; 1 8(a)(ii) (reaction that) gives out thermal energy ; 1 8(a)(iii) ;; ;; ;; oxygen correct = (1) products correct (either order) = (1) 2 8(b) (P) stays orange / orange-brown ; (Q) decolourises / (turns) colourless ; 2 8(c)(i) fractional distillation ; 1 8(c)(ii) (type of change) physical AND (explanation) no new substance is made / can be reversed ; 1 8(c)(iii) heating / cooking ; 1 8(d) natural gas ; coal ; 2

This question in 0653/32 May/June 2024

8 (a) The fossil fuel petroleum is a liquid mixture of hydrocarbons. (i) Complete the sentence about hydrocarbons. Hydrocarbons are molecules that contain … and … only. [1] (ii) Describe the arrangement and motion of particles in a liquid. arrangement … … motion … … [2] (iii) Explain why the change in state from a liquid to a gas is described as a physical change. … … [1] (b) A diagram of the equipment used to separate petroleum is shown in Fig. 8.1. column petroleum Fig. 8.1 State the name of the separation process that uses this equipment. … [1] (c) Ethene is an unsaturated hydrocarbon. (i) Describe what is meant by unsaturated. … [1] (ii) Naphtha is obtained from petroleum. Naphtha undergoes a process to produce ethene. State the name of the process that produces ethene from naphtha. … [1] (iii) State the name of the type of chemical reaction that changes ethene into poly(ethene). … [1] [Total: 8]

8 marks

Mark scheme: 8(a)(i) carbon and hydrogen ; 1 8(a)(ii) (arrangement) close together / random ; (motion) move around each other ; 2 8(a)(iii) no new substance is made / can be reversed ; 1 8(b) fractional distillation ; 1 8(c)(i) contains a (C=C) double bond ; 1 8(c)(ii) cracking ; 1 8(c)(iii) addition polymerisation ; 1

This question in 0653/33 May/June 2024

8 (a) Complete the sentences about fuels. Use words from the list. Each word may be used once or not at all. bitumen fossil hydrocarbon methane petroleum Coal, … and natural gas are … fuels. The main constituent of natural gas is … . [3] (b) Petroleum is separated into useful fractions by fractional distillation. Draw one line from each fraction to its use. fraction use fuel in cars refinery gas road surfaces naphtha chemical feedstock bitumen heating and cooking [3] (c) The diagrams in Fig. 8.1 show the structures of compound F and compound G. H H H H H H H C C C H H C C C H H H H H compound F compound G Fig. 8.1 (i) State the name of the group of hydrocarbons to which compound F belongs. … [1] (ii) Compound G is an unsaturated hydrocarbon. Describe what is meant by unsaturated. … … [1] (iii) Describe one chemical test to distinguish between compounds F and G. State the observation for each compound. test … compound F … compound G … [3] [Total: 11]

11 marks

Mark scheme: 8(a) petroleum ; 3 fossil ; methane ; 8(b) 3 fraction use fuel in cars refinery gas road surfaces naphtha chemical feedstock bitumen heating and cooking correct line for refinery gas ; correct line for naphtha ; correct line for bitumen ; 8(c)(i) alkane(s) ; 1 8(c)(ii) contains a carbon–carbon double bond ; 1 8(c)(iii) test add aqueous bromine ; 3 compound F no change ; compound G decolorises / turns (from red-orange to) colourless ;

This question in 0653/31 Oct/Nov 2024