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

1 (a) Fig. 1.1 shows part of the Periodic Table.
[Image_1: Periodic Table]
Answer the following questions using only the elements in Fig. 1.1. Each symbol of the element may be used once, more than once or not at all.
Give the symbol of the element that:
(i) produces a lilac colour in a flame test [1]
(ii) has an atom with only two occupied electron shells [1]
(iii) is an unreactive gas [1]
(iv) forms an ion that gives a white precipitate after the addition of excess sodium hydroxide [1]
(v) forms an ion with a charge of 2– [1]
(vi) is added to iron to make stainless steel. [1]
(b) Stainless steel is a mixture.
State two characteristics of a mixture.
1 [1]
2 [1]

2 (a) (i) State the meaning of the term diatomic. [1]
(ii) State the percentage of nitrogen in clean, dry air. [1]
(b) Ammonia has a simple molecular structure.
Complete Fig. 2.1 to show the dot-and-cross diagram for a molecule of ammonia. Show outer shell electrons only.
[Diagram: Fig. 2.1 Ammonia]
[2]
(c) Sodium chloride has a giant ionic structure of positive and negative ions.
(i) State the general name given to any positive ion. [1]
(ii) State one physical property of an ionic compound. [1]
(d) Graphite is used as an electrode.
(i) State one other use of graphite. [1]
(ii) Choose the correct statement that describes the structure and bonding in graphite.
Tick (✓) one box.
- simple covalent molecule
- giant ionic
- simple ionic
- giant covalent
[1]

3 (a) Polluted water can contain harmful substances such as plastics and phosphates. State two other types of harmful substance in polluted water.
1 [1]
2 [1]
(b) Table 3.1 shows the masses of ions, in mg, present in a 1000 cm³ sample of polluted water.
[Table_1: Ions in Polluted Water]
Answer these questions using the information from Table 3.1.
(i) Name the negative ion that has the lowest concentration. [1]
(ii) State the name of the NO₃^– ion. [1]
(iii) Calculate the mass of sodium ions in 250 cm³ of polluted water. [1]
(c) Fig. 3.1 shows some of the stages in the treatment of the domestic water supply.
sedimentation → filtration → use of carbon → ................................
[Diagram: Fig. 3.1]
(i) Complete Fig. 3.1 by adding the final stage. [1]
(ii) State why carbon is added to drinking water. [1]
(d) Describe how to test the purity of water using melting point. [2]
(e) Complete the symbol equation for the reaction of phosphorus(V) chloride, PCl₅, with water.
2PCl₅ + 8H₂O → .....H₃PO₄ + .....HCl [2]

4 (a) Fig. 4.1 shows the displayed formula of compound A.
[Diagram: Fig. 4.1]
(i) Explain why compound A is described as unsaturated. [1]
(ii) Explain why compound A is a hydrocarbon. [1]
(iii) Deduce the molecular formula of compound A. [1]
(b) Compound A reacts with steam to produce an alcohol.
(i) State the general formula for the homologous series of alcohols. [1]
(ii) Ethanol is an alcohol which can be manufactured by fermentation.
● Name two substances needed for fermentation.
1 [1]
2 [1]
● Give two conditions needed for fermentation.
1 [1]
2 [1]
(iii) State one use of ethanol. [1]
(c) A compound in the same homologous series as compound A reacts with ozone, O₃, to form compound B.
(i) Define the term homologous series. [2]
(ii) The molecular formula for compound B is C₆H₁₂O₃.
Complete Table 4.1 to calculate the relative molecular mass of C₆H₁₂O₃.
[Table_2: Relative Molecular Mass]
relative molecular mass = .............................. [2]

5 (a) Table 5.1 shows some properties of five halogens.
[Table_3: Properties of Halogens]
Use the information in Table 5.1 to predict:
(i) the melting point of iodine [1]
(ii) the atomic radius of fluorine [1]
(iii) the physical state of bromine at 0 °C. Give a reason for your answer.
physical state
reason [2]
(b) Aqueous chlorine reacts with aqueous potassium iodide.
(i) Complete the word equation for this reaction.
chlorine + potassium iodide → ........................ [2]
(ii) Explain why aqueous iodine does not react with aqueous potassium bromide. [1]
(c) Fluorine reacts with hot concentrated sodium hydroxide to produce sodium fluoride, water and oxygen.
(i) Complete the symbol equation for this reaction.
$2F_2 + 4NaOH ightarrow .....NaF + 2H_2O + ......$ [2]
(ii) Describe a test for oxygen.
test
observations [2]

6 (a) Metals are good electrical conductors. State three other typical physical properties of metals.
1 [1]
2 [1]
3 [1]
(b) (i) Complete Table 6.1 to show the number of electrons, neutrons and protons in the potassium atom and the nickel ion shown.
[Table_4: Electrons, Neutrons, and Protons]
(ii) Write the electronic configuration of the potassium atom. [1]
(c) Choose one property from the list that shows that nickel is a transition element.
Tick (✓) one box.
- has a low density
- forms coloured compounds
- has a low melting point
- does not act as a catalyst
[1]
(d) Nickel can be manufactured by reducing nickel(II) oxide with carbon monoxide and hydrogen.
$2NiO + CO + H_2 ightarrow 2Ni + H_2O + CO_2$
Explain how this equation shows that nickel(II) oxide is reduced. [1]
(e) Table 6.2 shows the observations when four different metals are heated with steam.
[Table_5: Observations with Steam]
Put the four metals in order of their reactivity.
Put the least reactive metal first. [2]

7 (a) Crystals of potassium chloride can be made by reacting an acid with an alkali.
(i) Name the acid and the alkali used.
acid [1]
alkali [1]
(ii) Choose from the list the type of reaction that takes place when an acid reacts with an alkali.
Draw a circle around your chosen answer.
addition neutralisation redox substitution [1]
(iii) Thymolphthalein is an acid–base indicator.
State the colour of thymolphthalein at pH 2 and at pH 12.
colour at pH 2 [1]
colour at pH 12 [1]
(iv) Describe how to make dry crystals of potassium chloride from an aqueous solution of potassium chloride. [2]
(b) Crystals of potassium chloride dissolve in water. This process is endothermic.
(i) Define the term endothermic. [1]
(ii) Fig. 7.1 shows the reaction pathway diagram for dissolving potassium chloride in water.
[Diagram: Fig. 7.1]
Answer the following questions using the information in Fig. 7.1.
● State the meaning of the state symbol (l).
● Explain how Fig. 7.1 shows that dissolving potassium chloride in water is endothermic. [2]

8 (a) A student investigates the reaction of small pieces of zinc with excess dilute sulfuric acid of three different concentrations.
The time taken for each reaction to finish is recorded. The three concentrations of the acid are:
● 0.2 mol/dm³
● 0.4 mol/dm³
● 0.8 mol/dm³
All other conditions stay the same.
Table 8.1 shows the time taken for each reaction to finish.
[Table_6: Reaction Times]
(i) Complete Table 8.1 by writing the concentrations in the first column. [1]
(ii) Describe the effect on the time taken for the reaction to finish when the reaction is carried out in the presence of a catalyst. All other conditions stay the same. [1]
(iii) Describe the effect on the time taken for the reaction to finish when larger pieces of zinc are used instead of small pieces of zinc. All other conditions stay the same. [1]
(b) Dilute sulfuric acid is electrolysed using inert electrodes.
(i) Name the products at the positive and negative electrodes.
product at the positive electrode [1]
product at the negative electrode [1]
(ii) Choose from the list the metal used as an inert electrode. Draw a circle around your chosen answer.
calcium magnesium platinum sodium [1]
(c) Zinc is a solid at room temperature. Describe the arrangement and separation of the particles in solid zinc.
arrangement
separation [2]