IGCSE Chemistry 0620/11 May/June 2025 Past Paper with Answers

Question 1

Which process happens when water vapour changes into rain?

1. condensing
2. boiling
3. evaporating
4. freezing

Question 2

Particle arrangements for three states of matter are labelled state 1, state 2 and state 3. In state 1 the particles are close together but arranged randomly (a liquid), in state 2 the particles are far apart and moving quickly in random directions (a gas), and in state 3 the particles are packed closely together in a fixed regular pattern (a solid). Which row correctly describes the change in the energy of the particles and in the particle motion for the stated change of state?

1. Change from state 3 to state 1: the energy of the particles increases and the particle motion increases.
2. Change from state 1 to state 2: the energy of the particles decreases and the particle motion decreases.
3. Change from state 2 to state 1: the energy of the particles decreases and the particle motion increases.
4. Change from state 1 to state 3: the energy of the particles increases and the particle motion decreases.

Question 3

An atom of element Q contains 19 electrons, 19 protons and 20 neutrons. What is element Q?

1. potassium
2. calcium
3. strontium
4. yttrium

Question 4 · Answer A

Step 1: A neutron has a relative mass of 1 and no charge (relative charge 0). Step 2: A proton also has mass 1 but a charge of +1, and an electron has almost no mass. Step 3: So the particle is the neutron.

Question 5 · Answer A

Step 1: Any isotope of boron must have 5 protons, and a neutral atom has equal protons and electrons, so 5 electrons. Step 2: Boron-11 already has 6 neutrons, so a different isotope must have a different neutron number, such as 5 neutrons (boron-10). Step 3: The row with 5 electrons, 5 neutrons and 5 protons fits.

Question 6 · Answer A

Step 1: Potassium iodide is ionic, made of potassium cations (positive) and iodide anions (negative), so statement 1 reverses the charges and is wrong. Step 2: Ionic compounds conduct when molten or dissolved because the ions are free to move, so statement 2 is correct. Step 3: Ions are formed by transferring electrons, not sharing, so statement 3 is wrong, leaving only statement 2.

Question 7 · Answer A

Step 1: Shared pairs of electrons are covalent bonds, found between non-metal atoms in molecules. Step 2: Methane and chlorine are molecules with covalent bonds, so they contain shared pairs. Step 3: Argon is a single unbonded atom and iron(III) oxide is ionic, so the answer is 2 and 4.

Question 8 · Answer A

Step 1: A giant covalent structure has many atoms joined by covalent bonds in a large network. Step 2: Diamond is a giant covalent structure of carbon atoms. Step 3: Ammonia, carbon dioxide and water are all small molecules, so the answer is diamond.

Question 9 · Answer A

Step 1: Sodium ions are $\text{Na}^+$ and carbonate ions are $\text{CO}_3^{2-}$, so two sodium ions balance one carbonate, giving $\text{Na}_2\text{CO}_3$. Step 2: Cobalt(II) chloride should be $\text{CoCl}_2$, xenon is a single atom $\text{Xe}$, and ammonium sulfate is $(\text{NH}_4)_2\text{SO}_4$. Step 3: Only sodium carbonate, $\text{Na}_2\text{CO}_3$, is written correctly.

Question 10 · Answer A

Step 1: Moles of $\text{MgCO}_3 = 21.0 \div 84 = 0.25$ mol. Step 2: The equation shows 1 mol of $\text{MgCO}_3$ gives 1 mol of $\text{MgO}$, so 0.25 mol of $\text{MgO}$ forms. Step 3: Mass of $\text{MgO} = 0.25 \times 40 = 10.0$ g.

Question 11 · Answer A

Step 1: Negative ions move to the positive electrode (anode). Step 2: In concentrated sodium chloride solution, chloride ions are discharged in preference to hydroxide, giving chlorine gas. Step 3: So the main product at the anode is chlorine.

Question 12 · Answer A

Step 1: Air is about 21% oxygen, so the volume of air needed is the oxygen volume divided by 0.21. Step 2: $630 \div 0.21 = 3000$. Step 3: So at least 3000 $\text{dm}^3$ of clean, dry air is needed.

Question 13 · Answer A

Step 1: Endothermic reactions take in energy, so the surroundings cool down, making statement 1 wrong. Step 2: Exothermic reactions release energy to the surroundings, so statement 2 is wrong. Step 3: In an exothermic reaction the products are at a lower energy than the reactants, so only statement 3 is correct.

Question 14 · Answer A

Step 1: A physical change does not make a new substance and can usually be reversed. Step 2: The metal melting (1) and water turning to steam (3) are changes of state, so they are physical. Step 3: Producing hydrogen (2) and raising the pH (4) involve new substances, so they are chemical, leaving 1 and 3.

Question 15 · Answer A

Step 1: A catalyst speeds up a reaction without being used up. Step 2: Because it is not consumed, the mass of the catalyst is the same before and after the reaction. Step 3: It does not change how much oxygen forms or the overall energy released.

Question 16 · Answer A

Step 1: Reduction is loss of oxygen and oxidation is gain of oxygen. Step 2: Copper(II) oxide loses oxygen to become copper, so CuO is reduced. Step 3: Carbon gains oxygen to form carbon dioxide, so carbon is oxidised, not reduced.

Question 17 · Answer A

Step 1: Aqueous sodium hydroxide is an alkali. Step 2: In an alkali, thymolphthalein is blue and methyl orange is yellow. Step 3: So the correct row is aqueous sodium hydroxide giving thymolphthalein blue and methyl orange yellow.

Question 18 · Answer A

Step 1: Damp red litmus turning blue shows an alkaline gas, which is ammonia. Step 2: Ammonia is released when an ammonium salt is warmed with a base, so one substance must be a base and the other an ammonium compound. Step 3: A basic oxide with ammonium chloride fits, so that is the correct pair.

Question 19 · Answer A

Step 1: Copper is too unreactive to react with dilute acid, so a copper compound must be used. Step 2: Copper(II) carbonate reacts with dilute sulfuric acid to give copper(II) sulfate, water and carbon dioxide. Step 3: So the reactants are dilute acid plus a metal carbonate.

Question 20 · Answer A

Step 1: Group number gives the number of outer electrons, and Group II atoms lose 2 electrons to form 2+ ions. Step 2: The table is ordered by proton number, not relative atomic mass, and elements in the same group (not period) have similar properties. Step 3: Group VII reactivity decreases down the group, so only the Group II statement is correct.

Question 21 · Answer A

Step 1: Metallic character increases towards the left-hand side of the Periodic Table. Step 2: The element on the far left is furthest into the metal region. Step 3: So the far left element shows the most metallic character.

Question 22 · Answer A

Step 1: Going down Group I, melting point falls and density generally rises. Step 2: A higher melting point than caesium and a lower density than sodium both point to an element near the top of the group. Step 3: Lithium is at the top of Group I, so E is lithium.

Question 23 · Answer A

Step 1: The halogen $\text{X}_2$ displaces $\text{Y}$ from its halide, so $\text{X}_2$ must be the more reactive halogen. Step 2: Chlorine is more reactive than iodine, so chlorine ($\text{X}_2$) displaces iodine from iodide ($\text{Y}^-$). Step 3: So $\text{X}_2$ is chlorine, $\text{Y}^-$ is iodide, and chlorine is more reactive than iodine.

Question 24 · Answer A

Step 1: High melting and boiling points, a coloured oxide and use as a catalyst are all typical of the transition elements. Step 2: Group I metals have low melting points, Group VII are non-metals, and Group VIII are unreactive gases. Step 3: So the element is one of the transition elements.

Question 25 · Answer A

Step 1: A metal that reacts with cold water is more reactive than one that only reacts with acid, which is more reactive than one that does not react at all. Step 2: T reacts vigorously with water (most reactive), Q reacts slowly with water, R reacts only with acid, and S does not react (least reactive). Step 3: From least to most reactive the order is S, R, Q, T.

Question 26 · Answer A

Step 1: Magnesium reacts with dilute sulfuric acid to give magnesium sulfate and hydrogen. Step 2: Magnesium also reacts with steam to give magnesium oxide and hydrogen. Step 3: So hydrogen is formed in both reactions.

Question 27 · Answer A

Step 1: The main ore of aluminium is bauxite, so statement 2 is correct. Step 2: Aluminium is less reactive than calcium, and it is extracted by electrolysis (not carbon) because it is above carbon in reactivity. Step 3: Brass is an alloy of copper and zinc, not aluminium, so only statement 2 is correct.

Question 28 · Answer A

Step 1: Cutlery must be hard and must resist corrosion from food and washing. Step 2: Stainless steel (type 3) is hard and resistant to corrosion, so it suits cutlery. Step 3: Types 1 and 2 both corrode, so only type 3 is suitable.

Question 29 · Answer A

Step 1: Grease stops the iron in tube P from rusting, so no oxygen is used and the water level does not change. Step 2: The untreated iron in tube Q rusts, using up the oxygen in the trapped air. Step 3: As oxygen is used up in tube Q the trapped gas volume falls and water rises, so P shows no change and Q rises.

Question 30 · Answer A

Step 1: The three elements needed are nitrogen (N), phosphorus (P) and potassium (K). Step 2: Potassium nitrate supplies potassium and nitrogen, and calcium phosphate supplies phosphorus. Step 3: Together they provide all three elements, so this is the correct pair.

Question 31 · Answer A

Step 1: The chemical tests for water use anhydrous cobalt(II) chloride (blue to pink) and anhydrous copper(II) sulfate (white to blue). Step 2: Litmus and methyl orange are indicators that test for acids and alkalis, not for water. Step 3: So substances 1 and 2 detect water.

Question 32 · Answer A

Step 1: Incomplete combustion happens when there is not enough oxygen. Step 2: Burning methane with too little oxygen produces carbon monoxide (and sometimes carbon) along with water. Step 3: So carbon monoxide is produced.

Question 33 · Answer A

Step 1: Members of a homologous series have the same functional group. Step 2: Because they share the same functional group, they have similar chemical properties. Step 3: So the correct row is similar chemical properties and the same functional group.

Question 34 · Answer A

Step 1: $\text{C}_4\text{H}_{10}$ is an alkane, which is saturated with only single bonds. Step 2: Alkanes react with chlorine by substitution, in which a chlorine atom replaces a hydrogen atom. Step 3: Alkanes do not undergo addition because they have no double bond, so the answer is chlorine by substitution.

Question 35 · Answer A

Step 1: Boiling point increases as the fractions get heavier, with larger molecules boiling at higher temperatures. Step 2: Gasoline and naphtha are light fractions, then kerosene, then diesel oil is heavier. Step 3: So the order of increasing boiling point is gasoline, naphtha, kerosene, diesel oil.

Question 36 · Answer A

Step 1: Cracking breaks large alkanes into smaller, more useful molecules including petrol, so statement 1 is correct. Step 2: Cracking produces both smaller alkanes and alkenes, so statement 2 (only alkenes) is wrong. Step 3: The alkenes made are used to make polymers, so statement 3 is correct, giving 1 and 3.

Question 37 · Answer A

Step 1: Ethene contains only carbon and hydrogen, so it is a hydrocarbon (1). Step 2: Ethene is the monomer used to make poly(ethene), so it is a monomer (2). Step 3: Ethene has a double bond, so it is unsaturated and reactive, making statements 3 and 4 wrong, leaving 1 and 2.

Question 38 · Answer A

Step 1: Measuring 25.00 $\text{cm}^3$ to two decimal places needs an accurate piece of apparatus. Step 2: A burette measures volumes accurately to the nearest 0.05 $\text{cm}^3$. Step 3: A beaker, measuring cylinder and dropping pipette are far less accurate, so a burette is most suitable.

Question 39 · Answer A

Step 1: After the reaction there is an insoluble solid (excess magnesium oxide) in a solution. Step 2: Filtration separates an insoluble solid from a liquid. Step 3: So filtration is used to remove the excess solid.

Question 40 · Answer A

Step 1: Copper(II) ions give a blue precipitate with aqueous sodium hydroxide. Step 2: Copper(II) sulfate is soluble, so there is no visible change with dilute sulfuric acid, and copper gives a blue-green flame. Step 3: All three results match copper(II) nitrate, so this row is correct.