Air quality and climate — Paper 3 · IGCSE Sciences - Co-ordinated (Double) 0654

3 (a) State the percentages of nitrogen and oxygen in clean air. nitrogen … % oxygen … % [2] (b) Fig. 3.1 shows a pie chart of the composition of a sample of polluted air taken in a busy city. Large numbers of cars and trucks travel through the city every day. other gases oxygen nitrogen Fig. 3.1 The section of the chart in Fig. 3.1 labelled other gases includes carbon monoxide. (i) Suggest how carbon monoxide is formed. … [1] (ii) State one harmful effect of carbon monoxide. … … [1] (c) Polluted air also contains oxides of nitrogen. Nitrogen dioxide, NO2, is a non-metallic oxide. Some nitrogen dioxide is dissolved in water containing full-range indicator (Universal Indicator). Predict the colour change observed in the liquid when the gas dissolves. Explain your answer. colour changes from … to … explanation … … [2] (d) Nitrogen molecules react with hydrogen molecules to make ammonia. Fig. 3.2 shows diagrams of the molecules involved in this reaction. H H H H N H N N H H H H N H H H Fig. 3.2 (i) State the chemical formula of an ammonia molecule. … [1] (ii) Use the examples in Fig. 3.2 to explain the difference between a molecule of an element and a molecule of a compound. … … … [2]

9 marks

Mark scheme: 3(a) 78 ; 21 ; 2 3(b)(i) incomplete combustion of fuel ; 1 3(b)(ii) toxic to humans ; 1 3(c) green to orange / red ; solution is acidic / non-metal oxides are acidic ; 2 3(d)(i) NH3 ; 1 3(d)(ii) elements contain only one type of atom ; compounds contain different atoms (bonded) ; any correct reference to the example molecules ; max 2

This question in 0654/31 May/June 2017

5 Human activities and natural events cause air pollution. Fig. 5.1 shows some of the gases that pass into the air during a volcanic eruption. water vapour carbon dioxide ash cloud sulfur dioxide carbon monoxide Fig. 5.1 (a) (i) State and explain which gas shown in Fig. 5.1 is responsible for increasing the acidity of rain. name … explanation … … [2] (ii) Acid rain reacts with limestone. Complete the word equation for the reaction between the acid in acid rain and the main compound in limestone. calcium … calcium … + + water + sulfate acid … … [3] (b) Table 5.1 shows the pH values of three colourless liquids, D, E and F. Table 5.1 liquid description pH D acid rain 4 E pure water … F dilute hydrochloric acid 1 (i) Complete Table 5.1. [1] (ii) A student compares the rate of reaction of these three liquids with magnesium. Fig. 5.2 shows what the student observes. D E F slow no visible fast bubbling reaction bubbling Fig. 5.2 Use the information in Table 5.1 to explain the observations for liquids D and F. … … … [2] (iii) Explain why the student must make sure that the temperature of the three liquids is the same. … … [1]

9 marks

Mark scheme: 5(a)(i) sulfur dioxide ; sulfur dioxide dissolves in / reacts with (rain) water / sulfur dioxide is a non-metal oxide ; 2 5(a)(ii) sulfuric (acid) ; (calcium) carbonate ; carbon dioxide ; 3 5(b)(i) 7 ; 1 5(b)(ii) liquid F is the most acidic ; so highest rate of reaction with magnesium / the more concentrated the acid the higher the rate that gas is produced ; 2 5(b)(iii) temperature also affects rate / reference to fair testing ; 1

This question in 0654/33 May/June 2017

5 (a) (i) State the percentage of nitrogen in the air. … % [1] (ii) Nitrogen and oxygen together make up most of the air. Name one other uncombined gaseous element in unpolluted air. … [1] (b) A student investigates the rusting of iron. Table 5.1 shows his experiments and the results. Table 5.1 test-tube experiment result air and water vapour A rust appears iron nail water dry air B no rust iron nail nitrogen gas and water vapour C no rust iron nail water (i) Explain why the iron nails in test-tube B and test-tube C do not rust. test-tube B … test-tube C … [2] (ii) Predict and explain if there is a change in the mass of test-tube A and its contents during the experiment. prediction … explanation … … [1] (c) Nitrogen is used to make ammonia, NH3. Ammonia gas dissolves in water to make an alkaline solution. (i) Describe a test to show that a solution of ammonia is alkaline. test … result … [2] (ii) Suggest the name of the acid that reacts with ammonia to form ammonium nitrate, NH4NO3. … [1] (iii) Explain why farmers add fertiliser containing ammonium nitrate to soil. … … … … [2]

10 marks

Mark scheme: 5(a)(i) 78 ; 1 5(a)(ii) argon / other noble gas ; 1 5(b)(i) B absence of water (vapour) / no water ; C absence of oxygen / no oxygen ; 2 5(b)(ii) no change in mass AND idea that nothing enters or leaves the test-tube ; 1 5(c)(i) use of named indicator e.g.(red) litmus ; correct result e.g. (litmus) turns blue ; 2 5(c)(ii) nitric acid ; 1 Question Answer Marks 5(c)(iii) idea of improving crop yield ; soil does not contain enough nutrients / nitrogen (compounds) or to replace nitrogen compounds ; reference to use of nitrogen in plants to produce amino acids / proteins / DNA ; max 2

This question in 0654/31 Oct/Nov 2017

8 Water is a neutral liquid. (a) (i) State the pH of pure water. … [1] (ii) Complete the general equation for neutralisation of an acid by an alkali. acid + alkali + [2] (iii) Explain the use of lime (calcium oxide) in the treatment of soil. … … … [2] (b) Sulfur dioxide, SO2, is a gas that is released into the air by human activity as well as natural processes. (i) Describe how sulfur dioxide is released into the air by human activity, … … a natural process. … … [2] (ii) State one way that sulfur dioxide in the atmosphere damages the environment. … … [1]

8 marks

Mark scheme: 8(a)(i) 7 ; 1 8(a)(ii) salt ; water ; 2 8(a)(iii) soil too acidic / calcium oxide is a base ; calcium oxide neutralises / reacts with the acid in the soil ; improves conditions for plant growth ; max 2 8(b)(i) burning fossil fuels (that still contain sulfur) ; reference to volcanism / hot springs ; 2 8(b)(ii) reference to the formation of acid rain / example of a consequence of acid rain ; 1

This question in 0654/32 Oct/Nov 2017

12 Coal, natural gas and biogas are all fuels that provide useful energy. Natural gas and biogas both contain methane. (a) (i) State the chemical formula of methane. … [1] (ii) State and explain what change, if any, is seen when methane is bubbled through aqueous bromine. change … explanation … … [1] (b) Natural gas is a fossil fuel. Biogas is a fuel produced by the decomposition of animal and plant waste. Fig. 12.1 shows the composition of natural gas and of biogas. other gases other gases carbon dioxide methane 95% methane 60% natural gas biogas Fig. 12.1 (i) Suggest how a sample of biogas can be tested to show that it contains carbon dioxide. test … result … [2] (ii) Suggest why natural gas is described as a fossil fuel. … … [1] (iii) When methane burns, the energy stored is converted into thermal energy. State the type of energy that is stored in fuels such as methane. … [1] (iv) Suggest why biogas releases less thermal energy than the same amount of natural gas. … … [1] (c) (i) Name a sulfur compound that is produced when coal burns. … [1] (ii) State one harmful effect on the environment of the compound named in (c)(i). … … [1]

9 marks

Mark scheme: 12(a)(i) CH4 ; 1 12(a)(ii) no change AND methane saturated / cannot be unsaturated ; 1 Question Answer Marks 12(b)(i) limewater ; turns milky ; 2 12(b)(ii) reference to time required to form / ovp ; 1 12(b)(iii) chemical ; 1 12(b)(iv) contains less flammable gas / only the methane can burn ; 1 12(c)(i) sulfur dioxide ; 1 12(c)(ii) reference to acid rain / consequence of acid rain ; 1

This question in 0654/33 Oct/Nov 2017

13 Fig. 13.1 shows a simplified diagram of the carbon cycle. carbon dioxide in atmosphere A D B C fossil carbon compounds fuels in animals carbon compounds in plants Fig. 13.1 (a) Name the process labelled C in Fig. 13.1. … [1] (b) Describe how an increase in process A contributes to global warming. … … … [2] (c) Explain why increasing the number of forested areas could reduce the rate of global warming. … … … [2] (d) The boxes on the left show some biological terms used when describing the organisms in a food chain. The boxes on the right show the meanings of these terms. Draw four lines to link each term with its meaning. term meaning an organism that gets its energy by carnivore feeding on other plants or animals an animal that gets its energy by eating consumer other animals an organism that makes its own organic herbivore nutrients using energy from the Sun an animal that gets its energy by eating producer plants [3]

8 marks

Mark scheme: 13(a) respiration ; 1 13(b) combustion releases carbon dioxide ; carbon dioxide is a greenhouse gas ; (enhanced) greenhouse effect leads to global warming ; max 2 13(c) ref photosynthesis ; remove carbon dioxide (from the atmosphere) / reducing greenhouse effect ; 2 13(d) term definition carnivore an organism that gets its energy by feeding on plants and animals consumer an animal that gets its energy by eating other animals. herbivore an organism that makes its own organic nutrients using energy from the Sun producer an animal that gets its energy by eating plants 1 correct ; 2 or 3 correct ; 4 correct ; 3

This question in 0654/31 Oct/Nov 2018

2 Air is a mixture of gases. Most of the air is made up of nitrogen and oxygen. (a) Fig. 2.1 shows pie charts representing two mixtures of gases J and K. These mixtures are different from clean air. other gases other gases nitrogen oxygen nitrogen oxygen mixture J mixture K Fig. 2.1 Describe one difference between clean air and: mixture J … … mixture K. … … [2] (b) The air in cities contains pollutants including carbon monoxide. (i) Describe how carbon monoxide is formed. … … [1] (ii) State why carbon monoxide is harmful to health. … … [1] (iii) Clean air contains small amounts of elements found in Group VIII of the Periodic Table. Identify the Group VIII element in the third period of the Periodic Table. … [1] (iv) Explain why clean air containing this Group VIII element is not harmful to humans. … … [1] (c) Fig. 2.2 shows diagrams of some of the molecules in air. O H H N N O C O O O Fig. 2.2 (i) On Fig. 2.2, draw a label line to a molecule of an element and label it E. Explain your answer. … … [1] (ii) On Fig. 2.2, draw a label line to the molecule of water and label it W. Explain your answer. … … [1] (iii) Describe a chemical test and its result to show that the air contains water. test … result … [2]

10 marks

Mark scheme: 2(a) J too great a proportion of other gases / too little oxygen; K nitrogen and oxygen the wrong way round; 2 2(b)(i) incomplete combustion of hydrocarbons / fuel; 1 2(b)(ii) toxic; 1 2(b)(iii) argon / Ar; 1 2(b)(iv) it is inert / does not react in the body; 1 2(c)(i) (label to either N2 or O2) only one type of atom; 1 2(c)(ii) (label to H2O) water molecules contain two hydrogen atoms and one oxygen atom; 1 2(c)(ii) cobalt chloride (paper); turns from blue to pink; 2

This question in 0654/32 Oct/Nov 2018

8 (a) Some volcanoes release the element sulfur. The sulfur sometimes catches fire, which is dangerous for people who collect the sulfur. (i) Name the element that combines with sulfur when it burns. … [1] (ii) Name the gas that is formed when sulfur burns. … [1] (iii) Suggest one harmful effect on health of the gas named in (a)(ii). … … [1] (b) Copper sulfate, CuSO4, and hydrogen sulfide, H2S, are compounds containing sulfur. (i) Copper sulfate also contains a transition element. State two general properties of compounds containing transition elements. 1 … 2 … [2] (ii) Predict the type of chemical bonding in hydrogen sulfide. Explain your answer. bonding … explanation … … [2] (iii) Iron sulfide is formed when a mixture of iron and sulfur is heated. Describe one way a student can show that a mixture of iron and sulfur is different from the compound iron sulfide. … … … [1]

8 marks

Mark scheme: 8(a)(i) oxygen ; 1 8(a)(ii) sulfur dioxide ; 1 8(a)(iii) sulfur dioxide is poisonous / causes breathing ; 1 8(b)(i) coloured compounds ; catalysts ; 2 8(b)(ii) covalent ; hydrogen sulfide is non-metal bonded to non-metal ; 2 8(b)(iii) idea that a magnet / water can separate the mixture or that dilute acid produces different gases with the mixture and compound or a lens shows separate pieces of sulfur and iron in the mixture or AVP ; 1

This question in 0654/33 Oct/Nov 2018

11 (a) State the names and percentages of the two main gases in air. gas 1 … percentage … % gas 2 … percentage … % [2] (b) Fig. 11.1 shows the composition of two gas mixtures Y and Z. gas mixture Y 100 % of gas 0 methane other gases gas mixture Z 100 % of gas 0 methane carbon nitrogen dioxide Fig. 11.1 (i) Deduce which gas mixture, Y or Z, is natural gas. Explain your answer. mixture … explanation … … [1] (ii) Describe how gas mixture Z is tested to show it contains carbon dioxide. test … result … [2] (c) Methane and propane are used as fuels. (i) Fig. 11.2 shows a molecule of propane. H H H H C C C H H H H Fig. 11.2 State why propane is described as: a hydrocarbon … … a saturated compound. … … [3] (ii) Identify the compounds that are produced by the complete combustion of methane. 1 … 2 … [2] [Total: 10]

10 marks

Mark scheme: 11(a) nitrogen 78% ; oxygen 21% ; 2 11(b)(i) (Y) natural gas is mainly methane / main gas in Z is not methane / owtte ; 1 11(b)(ii) limewater ; turns milky / cloudy / white precipitate ; 2 11(c)(i) hydrocarbon compound containing hydrogen and carbon ; only (hydrogen and carbon ) ; saturated contains only C-C single bonds ; 3 11(c)(ii) carbon dioxide / CO2 ; water (vapour) / H2O ; 2

This question in 0654/31 Oct/Nov 2019

5 Impurities are unwanted substances in mixtures. Impurities can be removed using purification techniques. (a) Some gaseous oxides are impurities which pollute air. (i) Name the gaseous oxide that forms when sulfur burns. … [1] (ii) Describe how this gaseous oxide can damage the environment. … … … [2] (iii) Identify two gaseous oxides, other than water vapour or carbon dioxide, that can form during the combustion of hydrocarbons in air. 1 … 2 … [2] (b) A scientist uses the apparatus shown in Fig. 5.1 to test four food dyes, P, Q, R and S. Fig. 5.2 shows her results for food dyes Q, R and S. container paper pencil line solvent (water) P Q R S P Q R S Fig. 5.1 Fig. 5.2 (i) Name this method the scientist uses to test the food dyes. … [1] (ii) Describe what happens inside the container that produces the results shown in Fig. 5.2. … … … … … [3] (iii) Food dye P is made by mixing together food dyes Q, R and S. Complete Fig. 5.2 by drawing the result for food dye P. [2] (iv) Suggest why impurities in food dyes must be removed before the dyes are used to colour food. … … [1] [Total: 12]

12 marks

Mark scheme: 5(a)(i) sulfur dioxide ; 1 5(a)(ii) causes acid rain ; effect of acid rain ; causes respiratory problems (in humans) ; max 2 2 5(a)(iii) carbon monoxide ; oxides of nitrogen / NOx / named oxide of nitrogen ; 2 5(b)(i) chromatography ; 1 5(b)(ii) water moves up the paper ; dyes carried along with the water / dyes dissolve in the water ; different dyes move at different speeds / move to different heights ; 3 5(b)(iii) three spots vertically in a line above the letter P ; shape, shading and heights of the spots all a reasonable attempt to reproduce the individual spots for Q R and S ; 2 5(b)(iv) the impurities may be poisonous / impurities affect the colour ; 1

This question in 0654/32 Oct/Nov 2019

8 Fig. 8.1 is a chart showing the composition of clean air. other gases oxygen nitrogen Fig. 8.1 (a) (i) Suggest the percentage of the section labelled other gases. Use your knowledge of the amounts of nitrogen and oxygen in air. percentage of other gases = … % [2] (ii) The other gases in Fig. 8.1 include very unreactive elements. State one of these unreactive elements. … [1] (iii) State, in terms of electronic structure of its atoms, why the element in (a)(ii) is unreactive. … … [1] (iv) State two harmful gaseous oxides that are present in polluted air. 1 … 2 … [2] (b) Fig. 8.2 shows apparatus used in the electrolysis of dilute sulfuric acid. oxygen dilute sulfuric acid + – d.c. power supply Fig. 8.2 (i) State the term used to describe the dilute sulfuric acid in this electrolysis experiment. … [1] (ii) Identify the gas produced at the cathode. … [1] (c) Fig. 8.3 shows apparatus a student uses to investigate the rate of reaction between calcium carbonate and dilute hydrochloric acid. cm3 dilute hydrochloric gas syringe acid stopclock calcium carbonate Fig. 8.3 (i) Complete the word equation for this reaction. hydrochloric calcium + + + acid carbonate [2] (ii) It takes 50 seconds for 80 cm3 of gas to collect in the gas syringe. Calculate the rate at which the gas is produced in cm3 / s. rate = … cm3 / s [1] (iii) State one change to the reaction conditions that reduces the rate of reaction. … … [1] [Total: 12]

12 marks

Mark scheme: 8(a)(i) nitrogen 78% + oxygen 21% = 99% / or equivalent ; so other gases = 100 – 99 = 1% ; 2 8(a)(ii) any noble gas ; 1 8(a)(iii) reference to full outer shell ; 1 8(a)(iv) sulfur dioxide / SO2 ; carbon monoxide / CO ; nitrogen oxides (named oxide) / NOx ; max 2 2 8(b)(i) electrolyte ; 1 8(b)(ii) hydrogen ; 1 8(c)(i) → calcium chloride ; + carbon dioxide + water ; 2 8(c)(ii) 80 ÷ 50 = 1.6 (cm3 / s) ; 1 8(c)(iii) decrease temperature / decrease acid concentration / decrease surface area of calcium carbonate ; 1

This question in 0654/33 Oct/Nov 2019

5 (a) Table 5.1 shows information about four metallic elements. Table 5.1 metal reaction of metal with water copper does not react with water iron reacts very slowly with water lithium reacts rapidly with water sodium reacts very rapidly with water (i) State the names of the two metals in Table 5.1 that are transition elements. … and … [1] (ii) Suggest the name of the gas produced when an alkali metal reacts with water. … [1] (iii) Place the four metals in order of reactivity from the most reactive to the least reactive. … most reactive … … … least reactive [2] (b) Copper is extracted by heating copper oxide with carbon. The word equation for the reaction is shown. copper oxide + carbon copper + carbon dioxide (i) Balance the symbol equation for this reaction. [1] … CuO + C … Cu + CO2 (ii) Identify which substance is reduced during this reaction. Explain your answer. substance reduced … explanation … [2] (c) During the extraction of copper, carbon dioxide is released into the air. Carbon dioxide is found in small quantities in clean air. (i) State the names of the two gases which are found in large quantities in clean air. … and … [1] (ii) Carbon dioxide is a greenhouse gas. State the name of one other greenhouse gas. … [1] (iii) Carbon dioxide is released into the air during the combustion of fossil fuels. State the names of two fossil fuels. … and … [1] [Total: 10]

10 marks

Mark scheme: 5(a)(i) copper and iron ; 1 5(a)(ii) hydrogen ; 1 5(a)(iii) sodium lithium iron copper ;; 2 5(b)(i) 2CuO + C → 2Cu + CO2 ; 1 5(b)(ii) copper oxide ; loses oxygen ; 2 Question Answer Marks 5(c)(i) oxygen and nitrogen ; (both required) 1 5(c)(ii) methane ; 1 5(c)(iii) coal / petroleum / natural gas – any two for 1 mark ; 1

This question in 0654/31 May/June 2021

5 (a) (i) State the percentage of oxygen and of nitrogen in a sample of clean air. oxygen … % nitrogen … % [2] (ii) A sample of air collected near a busy road contains carbon monoxide. Carbon monoxide is made by car engines. Describe how carbon monoxide is made by car engines. … … … … [3] (iii) State one harmful effect of carbon monoxide on the health of a human. … … [1] (b) The atmosphere contains small quantities of sulfur dioxide. Sulfur dioxide causes acid rain. (i) Suggest a pH for acid rain. … [1] (ii) Suggest one adverse effect of acid rain on buildings. … … [1] (iii) Sulfur dioxide is made when sulfur is burned in oxygen. This reaction is called an oxidation reaction. State the meaning of the term oxidation. … … [1] [Total: 9]

9 marks

Mark scheme: 5(a)(i) oxygen 21% ; nitrogen 78% ; 2 5(a)(ii) incomplete ; combustion ; of gasoline / hydrocarbon ; 3 5(a)(iii) carboxyhaemoglobin production / unconsciousness / death / poisoning ; 1 5(b)(i) any number less than 7 ; 1 5(b)(ii) corrosion of building materials ; 1 5(b)(iii) gain of oxygen ; 1

This question in 0654/32 Oct/Nov 2021

11 (a) Methane is a greenhouse gas. Name one other greenhouse gas. … [1] (b) Methane is completely combusted in oxygen. Carbon dioxide and water are made. Balance the symbol equation for this reaction. … … CH4 + O2 CO2 + H2O [2] (c) Complete Fig. 11.1 to show the structural formula of methane. C – H Fig. 11.1 [1] (d) Methane is the main constituent of a fossil fuel. (i) Name this fossil fuel. … [1] (ii) Name one other fossil fuel. … [1] (e) Methane is an alkane. Ethene is an alkene. (i) State the difference in structure between an alkane and an alkene. … … [1] (ii) A student uses a chemical reagent to show the difference between an alkane and an alkene. Tick (3) the correct box to show the chemical reagent used. aqueous bromine limewater litmus universal indicator [1] (f) Ethene, C2H4, reacts with steam to produce ethanol, C2H5OH. Ethene is a hydrocarbon. Explain why ethanol is not a hydrocarbon. … … [1] [Total: 9]

9 marks

Mark scheme: 11(a) carbon dioxide ; 1 11(b) (CH4 +) 2 (O2 → CO2 +) 2 (H2O) ;; 2 11(c) ; 1 11(d)(i) natural gas ; 1 11(d)(ii) coal / petroleum ; 1 11(e)(i) alkane has no double bonds C-C bonds / alkene has a C-C double bond / alkane has only single bonds ; 1 11(e)(ii) aqueous bromine ; 1 11(f) contains oxygen / does not just contain hydrogen and carbon ; 1

This question in 0654/32 Oct/Nov 2021

8 (a) Table 8.1 shows a list of covalently bonded molecules. Table 8.1 molecule Cl2 CO2 H2 HCl H2O NH3 (i) Identify two molecules from Table 8.1 that are elements. … and … [1] (ii) Identify one molecule from Table 8.1 that is diatomic. … [1] (iii) Identify one molecule from Table 8.1 which is a greenhouse gas. … [1] (b) (i) State the names of the two elements present in a molecule of ammonia, NH3. … and … [1] (ii) Determine the total number of atoms in a molecule of ammonia, NH3. … [1] (c) Water, H2O, is a solvent. State the meaning of the term solvent. … … [1] (d) Dilute hydrochloric acid reacts with calcium carbonate to produce carbon dioxide, water and a solution of a salt. (i) State which salt is produced. … [1] (ii) Suggest a method of obtaining a sample of the dry salt from this salt solution. … [1] (iii) When calcium carbonate and dilute hydrochloric acid react, the rate of reaction is slow. Suggest two ways of increasing the rate of reaction. 1 … 2 … [2] [Total: 10]

10 marks

Mark scheme: 8(a)(i) 8(a)(ii) HCl, / Cl2 / H2; 1 8(a)(iii) CO2 ; 1 8(b)(i) nitrogen and hydrogen; 1 8(b)(ii) 4; 1 8(c) a (liquid) in which other substances dissolve; 1 8(d)(i) calcium chloride; 1 8(d)(ii) evaporation; 1 8(d)(iii) increase temperature; increase surface area / decrease particle size; increase concentration of acid; 2

This question in 0654/32 Feb/March 2022

5 Fig. 5.1 shows three hydrocarbon molecules, A, B and C. Key carbon atom hydrogen atom A B C Fig. 5.1 (a) (i) Complete the dot-and-cross diagram of molecule C. Show the outer shell electrons only. [2] (ii) Molecule C is a greenhouse gas. State the name of one other greenhouse gas. … [1] (b) The reaction between molecule A and oxygen is exothermic. Describe what is meant by an exothermic reaction. … … [1] (c) State and explain which molecule A, B or C represents a molecule of ethane. molecule … explanation … … [1] (d) (i) State and explain which molecule A, B or C is unsaturated. molecule … explanation … … [1] (ii) An orange solution is used to test if a hydrocarbon molecule is unsaturated or saturated. State the name of this orange solution. … [1] (iii) Describe what is observed when the solution in (ii) is reacted with an unsaturated hydrocarbon molecule. … … [1] [Total: 8]

8 marks

Mark scheme: 5(a)(i) 1 shared pair ; 2 all else correct ; 5(a)(ii) water vapour ; carbon dioxide ; 1 5(b) (thermal) energy released ; 1 5(c) B – no mark and 1 has formula C2H6 ; 5(d)(i) A – no mark and 1 has two carbons but only four hydrogens / has general formula CnH2n ; 5(d)(ii) (aqueous) bromine ; 1 5(d)(iii) decolourises ; 1

This question in 0654/31 Oct/Nov 2022

5 (a) Fig. 5.1 is a chart showing the composition of clean air. other gases oxygen nitrogen Fig. 5.1 (not to scale) Use your knowledge of the composition of clean air to determine the percentage of other gases in clean air. Show your working. percentage = … % [2] (b) (i) Argon is one of the other gases in clean air. Use the Periodic Table on page 24 to determine the electronic structure of an argon atom. … [1] (ii) Use your answer to (b)(i) to explain why argon is very unreactive. … … [1] (iii) State one use for argon gas that depends on it being unreactive. … [1] (c) (i) Small quantities of carbon dioxide are found in the air. State one source of the carbon dioxide found in the air. … [1] (ii) Carbon dioxide is a compound formed from the elements carbon and oxygen. Describe the difference between an element and a compound. … … … [1] (iii) Carbon dioxide is a greenhouse gas. State the name of one other greenhouse gas. … [1] (d) (i) Water is neutral. State the pH value of pure water. pH = … [1] (ii) Carbon dioxide in the air dissolves in rainwater. This causes the rainwater to become slightly acidic. Suggest a pH value for this rainwater. pH = … [1] [Total: 10]

10 marks

Mark scheme: 5(a) 78% and/or 21% seen ; 2 other gases = 1% ; 5(b)(i) 2,8,8 ; 1 5(b)(ii) full outer shell ; 1 5(b)(iii) lamps; 1 5(c)(i) combustion of fossil fuels ; 1 5(c)(ii) any one from 1 (molecule of an) element contains only one type of atom ; compound consists of atoms of two or more elements (bound together) ; 5(c)(iii) methane ; 1 5(d)(i) 7 ; 1 5(d)(ii) 4–6 ; 1

This question in 0654/32 Feb/March 2023

5 A sample of clean air is a mixture of oxygen, nitrogen and small quantities of noble gases, water vapour and carbon dioxide. (a) State the percentage of oxygen gas and nitrogen gas in clean air. oxygen = … % nitrogen = … % [2] (b) State the name of a noble gas and give a use for this noble gas. name … use … … [2] (c) Water is made when hydrogen gas reacts with oxygen gas. Look at the symbol equation for the reaction between hydrogen and oxygen. This equation is not balanced. H2 + O2 H2O (i) Explain why this equation is not balanced. … … [1] (ii) Another way that water is made is by the decomposition of hydrogen peroxide, H2O2. Oxygen is also made. Balance the symbol equation for this reaction. … H2O2 … H2O + O2 [1] (iii) Complete the dot-and-cross diagram in Fig. 5.1 to show the bonding in a molecule of water, H2O. Show only the outer-shell electrons. O H H Fig. 5.1 [2] (iv) Name the type of chemical bonding in a molecule of water. … [1] (v) Describe a chemical test for water and give the positive result. test … positive result … … [2] [Total: 11]

11 marks

Mark scheme: 5(a) oxygen – 21% ; nitrogen – 78% ; 2 5(b) named noble gas ; correct use ; 2 5(c)(i) nos of oxygen atoms is different on LHS to RHS ; 1 5(c)(ii) 2 H2O2  2 H2O  O2 ; 1 5(c)(iii) 1 shared pair ; all else correct ; 2 5(c)(iv) covalent (bonds) ; 1 5(c)(v) anhydrous copper sulfate ; white to blue ; OR cobalt chloride (paper) ; blue to pink ; 2

This question in 0654/32 May/June 2023

5 A sample of clean air is a mixture of oxygen, nitrogen and small quantities of noble gases, water vapour and carbon dioxide. (a) State the percentage of oxygen gas and nitrogen gas in clean air. oxygen = … % nitrogen = … % [2] (b) State the name of a noble gas and give a use for this noble gas. name … use … … [2] (c) Water is made when hydrogen gas reacts with oxygen gas. Look at the symbol equation for the reaction between hydrogen and oxygen. This equation is not balanced. H2 + O2 H2O (i) Explain why this equation is not balanced. … … [1] (ii) Another way that water is made is by the decomposition of hydrogen peroxide, H2O2. Oxygen is also made. Balance the symbol equation for this reaction. … H2O2 … H2O + O2 [1] (iii) Complete the dot-and-cross diagram in Fig. 5.1 to show the bonding in a molecule of water, H2O. Show only the outer-shell electrons. O H H Fig. 5.1 [2] (iv) Name the type of chemical bonding in a molecule of water. … [1] (v) Describe a chemical test for water and give the positive result. test … positive result … … [2] [Total: 11]

11 marks

Mark scheme: 5(a) oxygen – 21% ; nitrogen – 78% ; 2 5(b) named noble gas ; correct use ; 2 5(c)(i) nos of oxygen atoms is different on LHS to RHS ; 1 5(c)(ii) 2 H2O2  2 H2O  O2 ; 1 5(c)(iii) 1 shared pair ; all else correct ; 2 5(c)(iv) covalent (bonds) ; 1 5(c)(v) anhydrous copper sulfate ; white to blue ; OR cobalt chloride (paper) ; blue to pink ; 2

This question in 0654/33 May/June 2023

2 (a) Air is a mixture of gases. Fig. 2.1 shows two pie charts representing samples of air, A and B. other gases other gases oxygen oxygen gas X gas X sample A sample B Fig. 2.1 (i) State which sample, A or B, represents clean air. Explain your answer. sample … explanation … … [1] (ii) Identify gas X. … [1] (b) Sulfur dioxide is a common pollutant found in air. (i) State one adverse effect of sulfur dioxide on the health of humans. … … [1] (ii) State one source of sulfur dioxide in the air. … [1] (iii) State one other common pollutant gas found in the air. … [1] (iv) Sulfur dioxide dissolves in rainwater to make acid rain. Suggest a pH value for acid rain. pH = … [1] (v) Farmers need to treat acidic soil to neutralise the acidity. State the chemical substance used by farmers to treat soil acidity. … [1] (c) An atom of sulfur has an electronic structure 2, 8, 6. (i) On Fig. 2.2, complete the electronic structure for this atom of sulfur. S Fig. 2.2 [1] (ii) Suggest how many electrons this sulfur atom gains to become a sulfide ion S2–. … [1] [Total: 9]

9 marks

Mark scheme: 2(a)(i) sample A (no mark) 1 idea that proportion of gases (other than Nitrogen) is correct ; ORA about sample B 2(a)(ii) nitrogen ; 1 2(b)(i) respiratory problems ; 1 2(b)(ii) combustion of fossil fuels (containing sulfur) / volcanoes ; 1 2(b)(iii) carbon monoxide / nitrogen oxides ; 1 2(b)(iv) 3-6 ; 1 2(b)(v) lime(stone) / CaCO3 / CaO / Ca(OH)2 ; 1 2(c)(i) 2 electrons in first shell and 1 8 electrons in 2nd shell and 6 electrons in 3rd shell ; 2(c)(ii) 2 ; 1

This question in 0654/31 Oct/Nov 2023

5 Table 5.1 shows five compounds, A, B, C, D and E, and the formula of each compound. Table 5.1 compound formula A CO B CO2 C CH4 D C2H4 E C2H6 (a) (i) State the compound from Table 5.1 that is an unsaturated hydrocarbon. … [1] (ii) Describe the chemical test that distinguishes between a saturated hydrocarbon and an unsaturated hydrocarbon and state the results for each. test … … result for a saturated hydrocarbon … … result for an unsaturated hydrocarbon … … [3] (b) (i) State the name of the two compounds from Table 5.1 that are possible products of the combustion of compound E. 1 … 2 … [2] (ii) State the name of the compound made when compound D reacts with steam. … [1] (iii) State the name of the polymer made using compound D as a monomer. … [1] (iv) Draw the structure of compound E, C2H6. [2] (c) State the names of the two most common greenhouse gases from Table 5.1. … and … [1] [Total: 11]

11 marks

Mark scheme: 5(a)(i) D ; 1 5(a)(ii) (aqueous) bromine ; 3 saturated – stays orange ; unsaturated – goes colourless ; 5(b)(i) carbon monoxide ; 2 carbon dioxide ; 5(b)(ii) ethanol ; 1 5(b)(iii) poly(ethene) ; 1 5(b)(iv) C–C single bond ; 2 3 hydrogens each attached to a different carbon atom ; 5(c) carbon dioxide and methane ; 1

This question in 0654/31 Oct/Nov 2023

5 (a) A sample of clean air contains nitrogen and other gases. State the percentage of nitrogen in the sample of clean air. … % [1] (b) Argon is one of the other gases found in clean air. Fig. 5.1 shows the electronic structure of an atom of argon. Fig. 5.1 (i) Use Fig. 5.1 to explain why argon is unreactive. … … [1] (ii) State one use for argon gas. … [1] (c) Sulfur dioxide is a pollutant in the air. (i) State one source of sulfur dioxide. … [1] (ii) Name one other oxide that is a pollutant in the air. … [1] (d) Sulfur dioxide contributes to acid rain. (i) Acid rain reacts slowly with limestone. Suggest one reason for this slow rate of reaction. … … [1] (ii) Acid rain also causes acidic soil. Name the chemical substance used by farmers to treat acidic soil. … [1] (iii) State the name of the type of reaction that occurs when the substance you have named in (d)(ii) is added to acidic soil. … [1] (e) Scientists are concerned about the increase in the amount of greenhouse gases in the Earth’s atmosphere. Name one greenhouse gas. … [1] [Total: 9]

9 marks

Mark scheme: 5(a) nitrogen 78% ; 1 5(b)(i) full outer shell / 1 no need to gain or lose electrons ; 5(b)(ii) lamps ; 1 5(c)(i) combustion of fossil fuels ; 1 5(c)(ii) oxides of nitrogen / carbon monoxide ; 1 5(d)(i) acid rain is (very) dilute ; 1 5(d)(ii) limestone / calcium carbonate ; 1 5(d)(iii) neutralisation ; 1 5(e) carbon dioxide / methane ; 1

This question in 0654/32 Feb/March 2024

11 (a) Iron is a metal. Circle three physical properties which are characteristic of metals. good electrical conductor high melting point low boiling point malleable poor thermal conductor [2] (b) Fig. 11.1 shows a spanner made from an alloy of iron. Fig. 11.1 The composition of the alloy is shown in Table 11.1. Table 11.1 element percentage composition % carbon chromium 2 iron 95 manganese 1 (i) Calculate the percentage of carbon in the alloy. percentage = … % [1] (ii) The mass of the spanner is 80 g. Calculate the mass of chromium contained in the spanner. mass of chromium = … g [1] (iii) Suggest why the spanner is made from an alloy of iron and not pure iron. … … [1] (c) Iron is extracted from iron oxide using carbon monoxide. iron oxide + carbon monoxide iron + carbon dioxide State the substance that is reduced in this reaction. … [1] (d) Iron reacts with two substances to make rust. (i) Name the element and the compound that react with iron to make rust. element … compound … [2] (ii) Barrier methods are used to stop iron rusting. Name one substance used in a barrier method of rust prevention. … [1] (e) Recycling iron costs less than extracting iron from iron ore. Suggest one other reason why iron needs to be recycled. … … [1] [Total: 10]

10 marks

Mark scheme: 11(a) good electrical conductor high melting point malleable 1 correct ; 3 correct ; 11(b)(i) 2% ; 1 11(b)(ii) 1.6 (g) ; 1 11(b)(iii) stronger ; 1 11(c) iron oxide ; 1 11(d)(i) element–oxygen ; compound–water ; 2 11(d)(ii) paint / oil / grease ; 1 11(e) iron is a finite resource ; 1

This question in 0654/33 May/June 2024

11 (a) The proton numbers and nucleon numbers of carbon and hydrogen are shown in Table 11.1. Table 11.1 proton number nucleon number carbon 6 12 hydrogen 1 1 (i) State the number of neutrons in a carbon atom and the number of neutrons in a hydrogen atom. carbon … hydrogen … [2] (ii) State the number of electrons in a carbon atom. … [1] (b) (i) State the difference between a saturated hydrocarbon and an unsaturated hydrocarbon. … … [1] (ii) Aqueous bromine is used to show the difference between a saturated hydrocarbon and an unsaturated hydrocarbon. Describe the result of the test with a saturated hydrocarbon. … … [1] (c) Fig. 11.1 shows the apparatus used for the catalytic cracking of a saturated hydrocarbon. catalyst reaction vessel saturated mixture of saturated hydrocarbons and unsaturated hydrocarbons Fig. 11.1 (i) State the purpose of the catalyst in the cracking of a saturated hydrocarbon. … … [1] (ii) Cracking is an endothermic reaction. State what is meant by an endothermic reaction. … … … [1] (d) The complete combustion of hydrocarbons produces the greenhouse gas carbon dioxide. (i) Name one other greenhouse gas. … [1] (ii) Identify the gas in the air that reacts with hydrocarbons during combustion. … [1] (iii) Carbon dioxide is one of the gases found in clean air. State the name of the two gases found in clean air in the greatest proportions. 1 … 2 … [2] [Total: 11]

11 marks

Mark scheme: 11(a)(i) carbon = 6 ; 2 hydrogen = 0 ; 11(a)(ii) 6 ; 1 11(b)(i) unsaturated has a C=C double bond ; 1 11(b)(ii) aqueous bromine remains orange ; 1 11(c)(i) speed up the reaction ; 1 11(c)(ii) temperature decreases / thermal energy is absorbed (from the surroundings) ; 1 11(d)(i) methane ; 1 11(d)(ii) oxygen ; 1 11(d)(iii) oxygen ; 2 nitrogen ;

This question in 0654/32 Oct/Nov 2024

11 (a) The proton numbers and nucleon numbers of carbon and hydrogen are shown in Table 11.1. Table 11.1 proton number nucleon number carbon 6 12 hydrogen 1 1 (i) State the number of neutrons in a carbon atom and the number of neutrons in a hydrogen atom. carbon … hydrogen … [2] (ii) State the number of electrons in a carbon atom. … [1] (b) (i) State the difference between a saturated hydrocarbon and an unsaturated hydrocarbon. … … [1] (ii) Aqueous bromine is used to show the difference between a saturated hydrocarbon and an unsaturated hydrocarbon. Describe the result of the test with a saturated hydrocarbon. … … [1] (c) Fig. 11.1 shows the apparatus used for the catalytic cracking of a saturated hydrocarbon. catalyst reaction vessel saturated mixture of saturated hydrocarbons and unsaturated hydrocarbons Fig. 11.1 (i) State the purpose of the catalyst in the cracking of a saturated hydrocarbon. … … [1] (ii) Cracking is an endothermic reaction. State what is meant by an endothermic reaction. … … … [1] (d) The complete combustion of hydrocarbons produces the greenhouse gas carbon dioxide. (i) Name one other greenhouse gas. … [1] (ii) Identify the gas in the air that reacts with hydrocarbons during combustion. … [1] (iii) Carbon dioxide is one of the gases found in clean air. State the name of the two gases found in clean air in the greatest proportions. 1 … 2 … [2] [Total: 11]

11 marks

Mark scheme: 11(a)(i) carbon = 6 ; 2 hydrogen = 0 ; 11(a)(ii) 6 ; 1 11(b)(i) unsaturated has a C=C double bond ; 1 11(b)(ii) aqueous bromine remains orange ; 1 11(c)(i) speed up the reaction ; 1 11(c)(ii) temperature decreases / thermal energy is absorbed (from the surroundings) ; 1 11(d)(i) methane ; 1 11(d)(ii) oxygen ; 1 11(d)(iii) oxygen ; 2 nitrogen ;

This question in 0654/33 Oct/Nov 2024

5 (a) The formulae of six gases found in the air are shown. CO CO2 He H2O N2 O2 Using these formulae: (i) State the formula for a monatomic gas. … [1] (ii) State the formula for a toxic gas. … [1] (iii) State the formula for the gas that makes up 78% of clean dry air. … [1] (iv) State the formula for an element. … [1] (v) State the formulae for the two substances that are needed to cause iron to rust. … and … [2] (b) Hydrogen chloride is a gas. Complete the dot‑and‑cross diagram in Fig. 5.1 to show the electron arrangement in a molecule of hydrogen chloride. Draw outer shell electrons only. H Cl Fig. 5.1 [2] (c) Hydrogen chloride dissolves in water to make dilute hydrochloric acid. Describe the effect of dilute hydrochloric acid on blue litmus indicator. … [1] (d) State the names of the two gaseous elements used in a fuel cell to produce electricity. 1 … 2 … [2] [Total: 11]

11 marks

Mark scheme: 5(a)(i) He ; 1 5(a)(ii) CO ; 1 5(a)(iii) N2 ; 1 5(a)(iv) He or N2 or O2 ; 1 5(a)(v) O2 ; 2 H2O ; 5(b) 2 shared pair correct ; all else correct ; 5(c) turns red ; 1 5(d) hydrogen ; 2 oxygen ;

This question in 0654/32 Oct/Nov 2025

6 (a) Ethane, C2H6, is an alkane. Ethene, C2H4, is an alkene. Complete the sentences to explain why alkanes are described as saturated and alkenes are described as unsaturated. Alkanes are saturated because they contain only … carbon–carbon covalent bonds. Alkenes are unsaturated because they contain a … covalent bond. [1] (b) Draw the displayed formula of ethane, C2H6. [2] (c) Determine the relative molecular mass, Mr, of ethane, C2H6. [Ar: C, 12; H, 1] relative molecular mass, Mr = … [2] (d) When ethane is completely combusted in oxygen, the two products are carbon dioxide gas and water vapour. (i) A chemical test for water is the use of anhydrous cobalt(II) chloride. State the colour change observed for a positive test. from … to … [2] (ii) The boiling point of a sample of water is 102 °C at standard atmospheric pressure. Explain how this shows that the sample of water is impure. … … … … [2] (iii) Higher levels of carbon dioxide in the atmosphere cause climate change. State and explain one strategy which will reduce the effects of climate change. strategy … … explanation … … … [2] [Total: 11]

11 marks

Mark scheme: 6(a) single and double ; 1 6(b) 2 carbon – carbon single bond ; all else correct ; 6(c) 24 + 6 or 2  12 + 6  1 ; 2 30 ; 6(d)(i) blue ; 2 (to) pink ; 6(d)(ii) pure water boils at 100 °C ; 2 impurities increase boiling point / AW ; 6(d)(iii) planting trees / planting plants ; 2 CO2 removed by trees / CO2 removed by plants ; OR reduction in livestock farming ; less CO2 emitted / less methane emitted ; OR decreasing use of fossil fuels ; less CO2 produced (during combustion) ; OR increasing use of hydrogen / increasing use of renewables ; no CO2 produced ;

This question in 0654/32 Oct/Nov 2025

5 (a) The formulae of six gases found in the air are shown. CO CO2 He H2O N2 O2 Using these formulae: (i) State the formula for a monatomic gas. … [1] (ii) State the formula for a toxic gas. … [1] (iii) State the formula for the gas that makes up 78% of clean dry air. … [1] (iv) State the formula for an element. … [1] (v) State the formulae for the two substances that are needed to cause iron to rust. … and … [2] (b) Hydrogen chloride is a gas. Complete the dot‑and‑cross diagram in Fig. 5.1 to show the electron arrangement in a molecule of hydrogen chloride. Draw outer shell electrons only. H Cl Fig. 5.1 [2] (c) Hydrogen chloride dissolves in water to make dilute hydrochloric acid. Describe the effect of dilute hydrochloric acid on blue litmus indicator. … [1] (d) State the names of the two gaseous elements used in a fuel cell to produce electricity. 1 … 2 … [2] [Total: 11]

11 marks

Mark scheme: 5(a)(i) He ; 1 5(a)(ii) CO ; 1 5(a)(iii) N2 ; 1 5(a)(iv) He or N2 or O2 ; 1 5(a)(v) O2 ; 2 H2O ; 5(b) 2 shared pair correct ; all else correct ; 5(c) turns red ; 1 5(d) hydrogen ; 2 oxygen ;

This question in 0654/33 Oct/Nov 2025