Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2023 Winter Zone 3

1. A list of substances is shown.
ammonia, calcium oxide, carbon monoxide, cobalt(II) chloride, ethane, ethanol, ethene, oxygen, potassium oxide, sodium sulfate, sulfuric acid, water
Answer the following questions using only the substances from the list. Each substance may be used once, more than once or not at all.
(a) Give the name of the substance that is a product of photosynthesis. [1]
(b) Give the name of the substance that is a member of the alkene homologous series. [1]
(c) Give the name of the substance that has an ion with a charge of 1−. [1]
(d) Give the name of the substance that is used to remove sulfur dioxide in flue gas desulfurisation. [1]
(e) Give the name of the substance that is the product formed in a hydrogen–oxygen fuel cell. [1]
(f) Give the name of the substance that is used to test for water. [1]

2. Hydrocarbons are compounds of carbon and hydrogen.
(a) State the meaning of the term compound. [2]
(b) Fig. 2.1 shows a fractionating column for separating petroleum into different hydrocarbon fractions.
[Image_1: Fractionating Column]
(i) On Fig. 2.1, draw an X inside the column to show where the hydrocarbon with the highest boiling point collects. [1]
(ii) Name the fraction labelled B in Fig. 2.1. [1]
(iii) State the name of the fraction which has hydrocarbons with the shortest chain length. [1]
(iv) State one use of the naphtha fraction. [1]

3. (a) Table 3.1 shows the average concentrations, in ng/1000 cm³, of air pollutants in four different years.
[Table_1: Concentration of Air Pollutants]
(i) Name the pollutant which has the highest concentration in 2019. [1]
(ii) Name the pollutant that shows a continuous decrease in concentration from 2019 to 2022. [1]
(iii) Calculate the average mass, in ng, of hydrocarbons in a 200 cm³ sample of polluted air in 2019. [mass =...] [1]
(b) (i) State one source of oxides of nitrogen in the air. [1]
(ii) Oxides of nitrogen contribute to acid rain. Give one other effect of oxides of nitrogen in the air. [1]
(iii) Unpolluted water has a neutral pH. Choose from the list the pH value of a neutral substance. [pH1, pH6, pH7, pH14] [1]
(c) Nitrogen dioxide is an acidic oxide. Choose an oxide from the list which is also an acidic oxide. Tick (√) one box. [Copper(II) oxide, Magnesium oxide, Phosphorus(V) oxide, Sodium oxide] [1]
(d) Sulfur dioxide reacts with oxygen to produce sulfur trioxide.
(i) Complete the symbol equation for this reaction:
...SO₂ + .... O₂ → 2SO₃ [2]
(ii) State the meaning of the symbol ⇌. [1]
(iii) Sulfur trioxide reacts with calcium oxide to produce calcium sulfate. Describe a test for sulfate ions. [Test:..., Observations:...] [2]

4. Nitrogen is a gas at room temperature.
(a) State two general properties of a gas. [2]
(b) Fig. 4.1 shows the physical states of nitrogen. [Image_2: Physical States of Nitrogen]
Name the changes of physical states A and B. [2]
(c) Describe solid nitrogen and nitrogen gas in terms of the arrangement and separation of the particles.
[Solid nitrogen: Arrangement:..., Separation:...]
[Nitrogen gas: Arrangement:..., Separation:...] [4]
(d) A sealed gas syringe contains 80 cm³ of nitrogen gas. State how increasing the pressure affects the volume of nitrogen gas in the gas syringe when the temperature remains constant. [1]

5. This question is about metals.
(a) Table 5.1 shows some properties of the Group I metals.
[Table_2: Properties of Group I Metals]
Use the information in Table 5.1 to predict:
(i) The melting point of rubidium. [1]
(ii) The atomic volume of potassium. [1]
(iii) The observations when sodium reacts with water. [1]
(iv) The physical state of sodium at 1300°C. Give a reason for your answer. [Physical state:..., Reason:...] [2]
(b) Iron is extracted in a blast furnace by reduction of iron(III) oxide.
(i) State the percentage of oxygen in clean, dry air. [1]
(ii) In the second step, carbon monoxide is produced by the reaction of carbon dioxide with carbon: CO₂ + C → 2CO
Choose the correct statement about this reaction. Tick (√) one box. [1]
(iii) In the third step, iron(III) oxide is reduced by carbon monoxide. The reaction is exothermic. State the meaning of the term exothermic. [2]
(c) Calcium carbonate is added to the blast furnace. The calcium carbonate breaks down as shown:
High temperature → Calcium carbonate → Calcium oxide + Carbon dioxide
(i) Name the type of chemical reaction that takes place. [1]
(ii) Complete this sentence about the calcium oxide that is produced in the blast furnace. Calcium oxide reacts with impurities in the iron ore to form .... [1]
(d) Table 5.2 gives the observations when four different metals react with air. [Table_3: Metal Reactivity with Air]
Put the four metals in order of their reactivity. Put the least reactive metal first. [2]

6. Hydrogen peroxide, H₂O₂, breaks down slowly at 40°C to produce oxygen gas and water.
$2\text{H}_2\text{O}_2 \rightarrow 2\text{H}_2\text{O} + \text{O}_2$
A student investigates the breakdown of hydrogen peroxide at 40°C in the presence of a catalyst.
(a) Fig. 6.1 shows the volume of oxygen gas released as the reaction proceeds. [Graph_1: Volume of Oxygen Gas]
(i) Deduce the volume of oxygen gas released after 15 seconds. [1]
(ii) The student repeats the experiment at 20°C. Draw a line on the grid in Fig. 6.1 to show how the volume of oxygen changes when the temperature of 20°C is used. [2]
(b) (i) The student repeats the experiment without a catalyst. All other conditions stay the same. Describe how the rate of reaction differs when no catalyst is used. [1]
(ii) The student repeats the experiment using a lower concentration of hydrogen peroxide. All other conditions stay the same. Describe how the rate of reaction differs when a lower concentration of hydrogen peroxide is used. [1]
(c) Hydrogen peroxide can act as a reducing agent in the presence of an alkali.
(i) State the meaning of the term alkali. [1]
(ii) Give the formula of the ion that is present in all alkaline solutions. [1]
(iii) State the colour of methyl orange in an alkaline solution. [1]
(iv) Aqueous ammonia is an alkali. Complete the word equation for the reaction of aqueous ammonia with hydrochloric acid:
Ammonia + Hydrochloric acid → .... [1]

7. Ethanoic acid and methacrylic acid are both carboxylic acids.
(a) Complete the word equation for the reaction of ethanoic acid with calcium:
Ethanoic acid + Calcium → .... [2]
(b) Ethanoic acid can be reduced to ethanol.
(i) Name the homologous series that includes ethanol. [1]
(ii) Ethanol can be manufactured by fermentation. Describe two conditions needed for fermentation. [2]
(c) Fig. 7.1 shows the displayed formula of methacrylic acid. [Diagram_1: Methacrylic Acid]
(i) On Fig. 7.1, draw a circle around the functional group which reacts with aqueous bromine. [1]
(ii) State the colour of aqueous bromine. [1]
(iii) Deduce the molecular formula of methacrylic acid. [1]
(d) Methacrylic acid can be converted to methyl methacrylate. The molecular formula of methyl methacrylate is C₅H₈O₂. Complete Table 7.1 to calculate the relative molecular mass of methyl methacrylate. [Table_4: Relative Molecular Mass Calculation] [2]
(e) Methyl methacrylate can be polymerised to produce a plastic. Describe two environmental problems caused by plastics. [2]
(f) Poly(ethene) is a polymer. Draw the displayed formula of the monomer used to make poly(ethene). [1]

8. Potassium chloride is an ionic compound.
(a) Complete Fig. 8.1 to show:
● The electronic configuration of a potassium ion
● The charge on the ion. [Image_3: Potassium Ion Configuration] [2]
(b) Deduce the number of protons and neutrons in the chloride ion shown. $^{37}\text{Cl}^-_{17}$
[Number of protons: ..., Number of neutrons: ...] [2]
(c) Molten potassium chloride is electrolysed using graphite electrodes.
(i) Define the term electrolysis. [2]
(ii) State the names of the products at each electrode and give the observations at the positive electrode:
[Product at the negative electrode: ..., Product at the positive electrode: ..., Observations at the positive electrode: ...] [3]
(d) Graphite electrodes are inert. Name one other inert electrode. [1]
(e) Graphite and diamond are two forms of carbon. Fig. 8.2 shows the structure of diamond. [Image_4: Structure of Diamond]
(i) Name the type of bonding in diamond. [1]
(ii) Use Fig. 8.2 to explain why diamond is used in cutting tools. [1]