Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2024 Summer Zone 1

Fig. 1.1 shows the structures of seven substances, A, B, C, D, E, F and G.
(a) Answer the following questions using only the structures in Fig. 1.1. Each structure may be used once, more than once, or not at all. State which structure represents:
(i) an alloy [1]
(ii) a substance that only conducts electricity when molten or in aqueous solution [1]
(iii) a giant covalent structure [1]
(iv) a compound that is a product formed in a hydrogen–oxygen fuel cell [1]
(v) a compound with a high melting point [1]
(vi) a gas that is responsible for increased global warming [1]
(b) Complete Fig. 1.2 to show the dot-and-cross diagram for structure C. Show the outer shell electrons only. [2]

(a) Table 2.1 shows the percentages by mass of the elements present in the human body. [Table_1]
Answer these questions using information from Table 2.1.
(i) Name the non-metallic element in Table 2.1 that has the lowest percentage by mass. [1]
(ii) Name an element in Table 2.1 that is in Period 4 of the Periodic Table. [1]
(b) Some medicines contain a compound made of $\text{Mg}^{2+}$ ions and $\text{OH}^{-}$ ions. Name the compound made of $\text{Mg}^{2+}$ ions and $\text{OH}^{-}$ ions. [1]
(c) Describe the observations when aqueous sodium hydroxide is added dropwise to a solution containing calcium ions until the sodium hydroxide is in excess.
observations with dropwise addition of sodium hydroxide
observations with excess sodium hydroxide [2]
(d) Name a calcium salt that is soluble in water. [1]
(e) Table 2.2 shows some properties of the Group I metals. [Table_2]
Use the information in Table 2.2 to predict:
● the melting point of potassium
● the observations when lithium reacts with water. [2]
(f) State how the density of the Group I elements changes down the group. [1]
(g) Sodium reacts with water to produce sodium hydroxide and a gas which pops with a lighted splint. Complete the symbol equation for this reaction. ....Na + 2H$_2$O → 2NaOH + ...... [2]

3 Aluminium is extracted by electrolysis of its purified ore.
(a) Name the main ore of aluminium. [1]
(b) Fig. 3.1 shows the apparatus used in the extraction of aluminium.
(i) Label the cathode in Fig. 3.1. [1]
(ii) The electrolyte contains molten aluminium oxide. State the product formed at each electrode.
positive electrode
negative electrode [2]
(c) State two physical properties that explain why aluminium is used in overhead electrical cables.
1
2 [2]
(d) Aluminium ore is purified by reacting it with sodium hydroxide. Sodium hydroxide is an alkali.
(i) State the meaning of the term alkali. [1]
(ii) Describe how to find the pH of a dilute solution of sodium hydroxide using universal indicator paper. [2]
(iii) A dilute solution of sodium hydroxide is added to a solution of methyl orange in acid until the sodium hydroxide is in excess. State the colour change of the methyl orange. from ... to ... [2]

(a) Fig. 4.1 shows the displayed formula of a compound extracted from a plant.
On Fig. 4.1, draw a circle around one functional group that makes this compound unsaturated. [1]
(b) A student extracts mixtures of coloured compounds from four different plants, Q, R, S and T. Fig. 4.2 shows the results of chromatography of these mixtures using an organic solvent.
(i) Deduce which plant, Q, R, S or T, contains the greatest number of coloured compounds. [1]
(ii) Deduce which two plants, Q, R, S or T, contain exactly the same coloured compounds. [1]
(iii) State the meaning of the term solvent. [1]
(c) (i) Plants produce glucose and oxygen by photosynthesis. Complete the word equation for photosynthesis. ... + ... → glucose + oxygen [2]
(ii) Name one other substance that is essential for photosynthesis. [1]

(a) An atom of carbon is represented by the symbol shown. $^{14}_6\text{C}$
Describe this atom of carbon in terms of:
● the position of the electrons, neutrons and protons in this atom
● the number of neutrons and number of protons
● the electronic configuration. [5]
(b) (i) Complete the symbol equation for the incomplete combustion of carbon to produce carbon monoxide. $...\text{C} + \text{O}_2 \rightarrow ...\text{CO}$ [2]
(ii) State one adverse effect of carbon monoxide. [1]
(c) Fig. 5.1 shows the displayed formula of chromium carbonyl.
Deduce the molecular formula of chromium carbonyl. [1]
(d) Another compound of chromium has the formula $\text{Na}_2\text{Cr}_2\text{C}_{10}\text{O}_{10}$. Complete Table 5.1 to calculate the relative molecular mass of $\text{Na}_2\text{Cr}_2\text{C}_{10}\text{O}_{10}$. [Table_3] [2]
(e) Chromium can be produced by heating chromium(III) oxide, $\text{Cr}_2\text{O}_3$, with carbon.
$\text{Cr}_2\text{O}_3 + 3\text{C} \rightarrow 2\text{Cr} + 3\text{CO}$
Describe how this equation shows that chromium(III) oxide is reduced. [1]

(a) Complete the equation by adding the missing state symbol. S(...) + O$_2$(g) → SO$_2$(g) [1]
(b) Fig. 6.1 shows how the mass of sulfur changes as the reaction proceeds.
Deduce the time taken for the reaction to finish. [1]
(c) The experiment is repeated using powdered sulfur. Describe the effect on the rate of reaction of using powdered sulfur rather than large pieces of sulfur. [1]
(d) Sulfur dioxide reacts with oxygen in a closed container.
2SO$_2$(g) + O$_2$(g) ⇌ 2SO$_3$(g)
(i) Describe the effect, if any, each of the following has on the rate of this reaction. All other conditions stay the same.
● The temperature is decreased.
● The pressure of the gases is increased. [2]
(ii) Changing concentration changes the rate of a reaction. Choose the correct unit of concentration from the list. [dm$^3$ /mol, mol/dm, mol/dm$^2$, mol/dm$^3$] [1]
(e) Sulfur dioxide is an air pollutant.
(i) State one adverse effect of sulfur dioxide. [1]
(ii) Emissions of sulfur dioxide can be reduced by using low-sulfur fossil fuels. State one other way of reducing sulfur dioxide emissions from fossil fuels. [1]
(f) Aqueous sodium hydrogen sulfite releases sulfur dioxide gas at room temperature. Sulfur dioxide changes the colour of acidified potassium manganate(VII) from purple to colourless. Fig. 6.2 shows a sealed tube with a small volume of aqueous sodium hydrogen sulfite at the bottom. A piece of filter paper soaked in acidified potassium manganate(VII) is attached to the top of the tube. The filter paper remains purple at first. The filter paper becomes colourless after a short time. Explain these results in terms of kinetic particle theory. [3]

(a) State three other physical properties of iron.
1
2
3 [3]
(b) (i) State the conditions needed for iron to rust. [2]
(ii) Rust is hydrated iron(III) oxide. State if iron(III) oxide is an acidic or basic oxide. Give a reason for your answer. [1]
(iii) Complete this sentence about methods of preventing rusting. Rusting can be prevented by painting or ... [1]
(c) The list shows five metals. calcium, copper, iron, silver, sodium. Put these metals in order of their reactivity. Put the most reactive metal at the top. least reactive most reactive [2]
(d) Complete the word equation for the reaction of calcium carbonate with nitric acid. calcium carbonate + nitric acid → ... + water + ... [2]

(a) Fig. 8.1 shows the displayed formulae of five organic compounds, V, W, X, Y and Z.
(i) State which two of the compounds, V, W, X, Y and Z, are in the same homologous series. ... and ... [1]
(ii) Explain why compound V is an alkane. [2]
(iii) State the name of the homologous series to which compound X belongs. [1]
(b) Ethanol can be manufactured by the catalytic addition of steam to ethene.
(i) State the temperature and pressure required for this reaction.
temperature ... °C
pressure ... atm [2]
(ii) Name one other method of manufacturing ethanol. [1]
(c) Describe how alkenes are manufactured from petroleum fractions. [2]