2 (a) Magnesium is in Period 3 of the Periodic Table. (i) Use the Periodic Table to name the noble gas in Period 3 of the Periodic Table. … [1] (ii) Describe the change in metallic character across Period 3. … … [1] (b) Magnesium reacts with carbon dioxide. Magnesium oxide and carbon are made. (i) Write the word equation for this reaction. … + … … + … [1] (ii) The reaction between magnesium and carbon dioxide is exothermic. Explain what is meant by an exothermic reaction. … … [1] (c) An atom of magnesium has a proton number (atomic number) of 12 and a nucleon number (mass number) of 24. Complete Table 2.1 to show the names and numbers of the two particles contained in the nucleus of this magnesium atom. Table 2.1 name of particle number of particles [2] (d) Magnesium carbonate reacts with dilute hydrochloric acid to make aqueous magnesium chloride. (i) Magnesium carbonate is insoluble in water. State the separation technique used to remove magnesium carbonate from a mixture of magnesium carbonate and water. … [1] (ii) Magnesium chloride dissolves in water. State the separation technique used to obtain solid magnesium chloride from a solution of magnesium chloride. … [1] (iii) Magnesium carbonate reacts with dilute hydrochloric acid. Complete the balanced symbol equation for this reaction. MgCO3 + …HCl MgCl 2 + CO2 + H2O [1] (iv) Dilute hydrochloric acid contains aqueous chloride ions. State the test for aqueous chloride ions and give the observation for a positive result. test … observation … [2] (e) Table 2.2 shows the composition of a magnesium alloy. Table 2.2 element % by mass magnesium 94 neodymium 2 yttrium 4 (i) Calculate the mass of magnesium in 500 kg of the alloy. … kg [1] (ii) The alloy is used in aircraft bodies. Suggest why the alloy of magnesium is used rather than pure magnesium for aircraft bodies. … … [1] [Total: 13]

2(a)(i) argon ; 1 2(a)(ii) metal to non-metal ; 1 2(b)(i) magnesium + carbon dioxide → carbon + magnesium oxide ; 1 2(b)(ii) thermal energy released ; 1 2(c) protons –12 ; neutrons –12 ; 2 2(d)(i) filtration ; 1 2(d)(ii) crystallisation ; 1 2(d)(iii) MgCO3 + 2HCl → MgCl2 + CO2 + H2O ; 1 2(d)(iv) (acidified) (aqueous) silver nitrate ; white precipitate ; 2 2(e)(i) 470 (kg) ; 1 2(e)(ii) stronger / less dense ; 1 (a)(i) To earn this mark, you must correctly identify 'argon' as the noble gas in Period 3. (a)(ii) To earn this mark, you must describe the change in metallic character across Period 3 as going from 'metal to non-metal'. (b)(i) To earn this mark, you must write the correct word equation: 'magnesium + carbon dioxide → carbon + magnesium oxide'. (b)(ii) To earn this mark, you must explain that an exothermic reaction is one where 'thermal energy is released'. (c) To earn these two marks, you must correctly state that the nucleus contains 'protons – 12' and 'neutrons – 12'. (d)(i) To earn this mark, you must identify 'filtration' as the correct separation technique. (d)(ii) To earn this mark, you must identify 'crystallisation' as the correct separation technique. (d)(iii) To earn this mark, you must write the correct balanced chemical equation: 'MgCO3 + 2HCl → MgCl2 + CO2 + H2O'. (d)(iv) To earn these two marks, you must state the use of '(acidified) (aqueous) silver nitrate' and observe a 'white precipitate'. (e)(i) To earn this mark, you must state the correct value '470 (kg)'. (e)(ii) To earn this mark, you must state that the alloy is 'stronger / less dense' than pure magnesium.

2 (a) Magnesium is in Period 3 of the Periodic Table. (i) Use the Periodic Table to name the noble gas in Period 3 of the Periodic Table. … [1] (ii) Describe the change in metallic character across Period 3. … … [1] (b) Magnesium reacts with carbon dioxide. Magnesium oxide and carbon are made. (i) Write the word equation for this reaction. … + … … + … [1] (ii) The reaction between magnesium and carbon dioxide is exothermic. Explain what is meant by an exothermic reaction. … … [1] (c) An atom of magnesium has a proton number (atomic number) of 12 and a nucleon number (mass number) of 24. Complete Table 2.1 to show the names and numbers of the two particles contained in the nucleus of this magnesium atom. Table 2.1 name of particle number of particles [2] (d) Magnesium carbonate reacts with dilute hydrochloric acid to make aqueous magnesium chloride. (i) Magnesium carbonate is insoluble in water. State the separation technique used to remove magnesium carbonate from a mixture of magnesium carbonate and water. … [1] (ii) Magnesium chloride dissolves in water. State the separation technique used to obtain solid magnesium chloride from a solution of magnesium chloride. … [1] (iii) Magnesium carbonate reacts with dilute hydrochloric acid. Complete the balanced symbol equation for this reaction. MgCO3 + …HCl MgCl 2 + CO2 + H2O [1] (iv) Dilute hydrochloric acid contains aqueous chloride ions. State the test for aqueous chloride ions and give the observation for a positive result. test … observation … [2] (e) Table 2.2 shows the composition of a magnesium alloy. Table 2.2 element % by mass magnesium 94 neodymium 2 yttrium 4 (i) Calculate the mass of magnesium in 500 kg of the alloy. … kg [1] (ii) The alloy is used in aircraft bodies. Suggest why the alloy of magnesium is used rather than pure magnesium for aircraft bodies. … … [1] [Total: 13]

2(a)(i) argon ; 1 2(a)(ii) metal to non-metal ; 1 2(b)(i) magnesium + carbon dioxide → carbon + magnesium oxide ; 1 2(b)(ii) thermal energy released ; 1 2(c) protons –12 ; neutrons –12 ; 2 2(d)(i) filtration ; 1 2(d)(ii) crystallisation ; 1 2(d)(iii) MgCO3 + 2HCl → MgCl2 + CO2 + H2O ; 1 2(d)(iv) (acidified) (aqueous) silver nitrate ; white precipitate ; 2 2(e)(i) 470 (kg) ; 1 2(e)(ii) stronger / less dense ; 1 (a)(i) To earn this mark, you must correctly identify 'argon' as the noble gas in Period 3. (a)(ii) To earn this mark, you must describe the change in metallic character across Period 3 as going from 'metal to non-metal'. (b)(i) To earn this mark, you must write the correct word equation: 'magnesium + carbon dioxide → carbon + magnesium oxide'. (b)(ii) To earn this mark, you must explain that an exothermic reaction is one where 'thermal energy is released'. (c) To earn these two marks, you must correctly state that the nucleus contains 'protons – 12' and 'neutrons – 12'. (d)(i) To earn this mark, you must identify 'filtration' as the correct separation technique. (d)(ii) To earn this mark, you must identify 'crystallisation' as the correct separation technique. (d)(iii) To earn this mark, you must write the correct balanced chemical equation: 'MgCO3 + 2HCl → MgCl2 + CO2 + H2O'. (d)(iv) To earn these two marks, you must state the use of '(acidified) (aqueous) silver nitrate' and observe a 'white precipitate'. (e)(i) To earn this mark, you must state the correct value '470 (kg)'. (e)(ii) To earn this mark, you must state that the alloy is 'stronger' or 'less dense' than pure magnesium.

2 (a) The thermal decomposition of calcium carbonate makes calcium oxide and carbon dioxide. (i) Write the word equation for the thermal decomposition of calcium carbonate. + [1] (ii) The production of lime (calcium oxide) from limestone (calcium carbonate) is one use of limestone. State one other use of limestone. … [1] (iii) Calcium carbonate has the formula CaCO3. State the number of different elements present in calcium carbonate. … [1] (iv) Explain why the thermal decomposition of calcium carbonate is a chemical change and not a physical change. … … [1] (v) The thermal decomposition of calcium carbonate is an endothermic reaction. State what is meant by an endothermic reaction. … … … [1] (b) (i) Carbon dioxide is a compound but carbon is an element. State the difference between an element and a compound. … … … [2] (ii) Carbon is a solid and carbon dioxide is a gas. Complete Table 2.1 to describe the differences between a solid and a gas. One difference has been done for you. Table 2.1 particle separation particle arrangement particle motion solid vibrate about a fixed point gas move rapidly in all directions [2] (c) Carbon exists in many forms including diamond and graphite. Diamond and graphite are described as giant covalent structures. Fig. 2.1 shows three covalent structures, A, B and C. A B C carbon atom Fig. 2.1 (i) State which structure represents diamond. Choose from A, B or C. … [1] (ii) State which structure represents graphite. Choose from A, B or C. … [1] (iii) State why the bonding between the carbon atoms in diamond is covalent and not ionic. … … [1] [Total: 12]

2(a)(i) calcium carbonate → calcium oxide + carbon dioxide ; 1 2(a)(ii) neutralizing acidic soil / building material / cement ; 1 2(a)(iii) 3 ; 1 2(a)(iv) new substances produced ; 1 2(a)(v) (thermal) energy taken in ; 1 2(b)(i) an element contains only one type of atom ; a compound contains two or more elements chemically combined ; 2 2(b)(ii) particles separation particle arrangement particle motion solid close together regular vibrate about a fixed point gas far apart random move rapidly in all directions particle separation column ; particle arrangement column ; 2 2(c)(i) A ; 1 2(c)(ii) B ; 1 2(c)(iii) 2 non-metal atoms bonding / electrons are shared ; 1 (a)(i) To earn this mark, you must write the correct word equation for the thermal decomposition of calcium carbonate, including the arrow and plus signs. (a)(ii) You need to state any one valid use of limestone, such as neutralizing acidic soil, as a building material, or for cement. (a)(iii) To get this mark, you must correctly identify the number of different elements present in the formula CaCO3. (a)(iv) You earn this mark by explaining that new substances are produced during the thermal decomposition. (a)(v) This mark is awarded for stating that an endothermic reaction involves the taking in of thermal energy. (b)(i) You must define an element as containing only one type of atom and a compound as containing two or more elements chemically combined. (b)(ii) You need to correctly fill in the 'particle separation' and 'particle arrangement' columns for both solid and gas, showing close together/regular for solid and far apart/random for gas. (c)(i) You must select option A. (c)(ii) You must select option B. (c)(iii) You need to explain that covalent bonding involves two non-metal atoms bonding or that electrons are shared.

2 (a) Table 2.1 shows the melting points and reactivity with water of three Group I metals. Table 2.1 element melting point / °C reactivity with water lithium 181 … sodium 98 forms bubbles of gas rapidly potassium … forms bubbles of gas very rapidly Complete Table 2.1 to predict • the melting point of potassium • the reactivity of lithium with water. [2] (b) Name the gas made when a Group I metal reacts with water. … [1] (c) When sodium reacts with chlorine, an orange flame is seen and the sodium melts. Sodium chloride is formed. (i) State if the reaction is exothermic or endothermic. Explain your answer. reaction is … explanation … … [1] (ii) Sodium chloride contains chloride ions. Describe a test for chloride ions and the positive result. test … result … [2] (iii) State the type of bonding present in sodium chloride. Explain your answer. type of bonding … explanation … … [2] (d) Concentrated aqueous sodium chloride is electrolysed. State the products at the electrodes. … and … [2] (e) A student separates a mixture of sand and aqueous sodium chloride. (i) State the method of separation used to separate the sand from the aqueous sodium chloride. … [1] (ii) Describe how solid sodium chloride can be obtained from aqueous sodium chloride. … … [1] [Total: 12]

2(a) below 90 °C ; reacts / forms bubbles of gas slowly / moderately ; 2 2(b) hydrogen ; 1 2(c)(i) exothermic because (thermal) energy released (to melt sodium) ; 1 2(c)(ii) aqueous silver nitrate ; white precipitate ; 2 2(c)(iii) ionic ; bonding between a metal and a non-metal / electron transfer ; 2 2(d) hydrogen ; chlorine ; 2 2(e)(i) filtration ; 1 2(e)(ii) evaporation / crystallisation ; 1 To earn marks, you must correctly predict potassium's melting point as below 90°C and lithium's reactivity as slowly forming bubbles of gas. For part (b), state 'hydrogen'. For (c)(i), identify the reaction as 'exothermic' and explain that thermal energy is released. For (c)(ii), describe the test as adding aqueous silver nitrate and the positive result as a 'white precipitate'.

17 The diagram shows the energy change for the reactions between hydrogen and the halogens. The reaction is H2 + X2  2HX. The size of the energy change is different for each halogen. energy H2 + X2 progress of reaction 2HX energy change The diagram shows that the reactions are ……1…… . The most reactive halogen is ……2…… and therefore the energy change for this element is ……3…… . Which words complete gaps 1, 2 and 3? 1 2 3 A endothermic fluorine least B endothermic iodine least C exothermic fluorine greatest D exothermic iodine greatest

Answer: C To earn the mark, a student must correctly identify that the reactions are exothermic, fluorine is the most reactive halogen, and therefore the energy change for fluorine is the greatest.

Cambridge IGCSE Co-ordinated Sciences · 0654

IGCSE Co-ordinated Sciences (0654) Chemical energetics past paper questions

Revise IGCSE Co-ordinated Sciences (0654) — Chemical energetics with real Cambridge past-paper questions grouped by topic, each shown with its marking scheme. Working one topic at a time targets exactly the skill each question tests.

107 free questions from 2016–2021, each with its marking scheme. Open the full topical bank to filter by subtopic, paper, and year.

Chemical energetics in IGCSE Co-ordinated Sciences 0654 exams, 2020–2025

Across 2020–2025, Chemical energetics accounted for 139 questions worth 886 marks in Cambridge IGCSE Co-ordinated Sciences (0654) papers.

By year
Year	Questions	Marks
2020	21	134
2021	24	161
2022	23	130
2023	23	190
2024	25	152
2025	23	119

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C5.1 Exothermic and endothermic reactions826 marks

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Paper 1 · 35 qs
Paper 2 · 25 qs
Paper 3 · 29 qs
Paper 4 · 28 qs
Paper 5 · 11 qs
Paper 6 · 11 qs

All most-tested Co-ordinated Sciences topics

2021 May/Jun · Paper 3 · Q2 · 13 marks
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2021 May/Jun · Paper 3 · Q2 · 13 marks
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2021 Oct/Nov · Paper 3 · Q2 · 12 marks
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2021 Oct/Nov · Paper 3 · Q2 · 12 marks
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2021 Feb/Mar · Paper 1 · Q17 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q17
Answer: C
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