Total marks: 80 · Duration: 75 minutes · Tier: Core
Instructions to candidates
- Answer all questions.
- Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs.
- Write your answers in the spaces provided.
- You may use a calculator.
- Where a question describes apparatus or a chromatogram in words, you may find it helpful to sketch it.
Information
- The total mark for this paper is 80.
- The number of marks for each question or part question is shown in brackets.
- This paper covers the Core content of the Cambridge IGCSE Chemistry (0620) syllabus.
- Relative atomic masses (Ar): H = 1, C = 12, N = 14, O = 16, Mg = 24, Al = 27, S = 32, Ca = 40, Cu = 64.
Paper
Question 1 — States of matter and separating mixtures (11 marks)
(a) Name the change of state when:
(i) a solid turns into a liquid [1 mark]
(ii) a gas turns into a liquid. [1 mark]
(b) Describe the arrangement and the motion of the particles in a gas. [2 marks]
(c) A purple crystal of potassium manganate(VII) is placed at the bottom of a beaker of water. After an hour, the purple colour has spread through all the water, although the water was not stirred.
Name this process and explain why it happens. [2 marks]
(d) Name the method you would use to:
(i) obtain sand from a mixture of sand and water [1 mark]
(ii) obtain pure water from salt solution [1 mark]
(iii) separate the dyes in a sample of ink. [1 mark]
(e) A student uses chromatography to analyse a food colouring, E, and three known dyes, P, Q and R. The chromatogram of E has three spots. Two of the spots are at the same heights as the spots for P and R. The third spot does not match any of the known dyes.
What does this show about the food colouring E? [2 marks]
Question 2 — Atoms, ions and bonding (12 marks)
(a) A fluorine atom is represented as ¹⁹₉F. Give the number of protons, neutrons and electrons in this atom. [2 marks]
(b) (i) Give the electronic configuration of a magnesium atom (atomic number 12). [1 mark]
(ii) State the group and the period of magnesium in the Periodic Table. Explain how you can tell this from its electronic configuration. [2 marks]
(c) What is meant by the term isotopes? [1 mark]
(d) Describe how a sodium atom becomes a sodium ion. [2 marks]
(e) Give two physical properties of ionic compounds such as sodium chloride. [2 marks]
(f) Graphite is a form of carbon. Give one use of graphite and explain how its structure makes it suitable for this use. [2 marks]
Question 3 — Formulae and equations (10 marks)
(a) Calculate the relative formula mass (Mr) of:
(i) calcium carbonate, CaCO₃ [1 mark]
(ii) ammonium sulfate, (NH₄)₂SO₄. [1 mark]
(b) (i) Balance the symbol equation for burning magnesium:
___ Mg + O₂ → ___ MgO [1 mark]
(ii) Write a word equation for the reaction of zinc with dilute hydrochloric acid. [1 mark]
(c) Give the formula of:
(i) aluminium oxide (Al³⁺ and O²⁻ ions) [1 mark]
(ii) calcium hydroxide (Ca²⁺ and OH⁻ ions). [1 mark]
(d) A student dissolves 10.0 g of sugar in water and makes the solution up to 0.250 dm³. Calculate the concentration of the solution in g/dm³. [2 marks]
(e) Calculate the percentage by mass of copper in copper(II) oxide, CuO. [2 marks]
Question 4 — Electrolysis and energy changes (11 marks)
(a) What is meant by electrolysis? [1 mark]
(b) Molten lead(II) bromide is electrolysed using inert electrodes.
(i) Name the product at the cathode. [1 mark]
(ii) Name the product at the anode. [1 mark]
(iii) Describe what is seen at the anode. [1 mark]
(c) Concentrated aqueous sodium chloride is electrolysed using inert electrodes. Name the product at:
(i) the anode [1 mark]
(ii) the cathode. [1 mark]
(d) Give two reasons why metal objects are electroplated. [2 marks]
(e) A student mixes pairs of solutions and measures the temperature before and after mixing.
| Reaction | Starting temperature (°C) | Final temperature (°C) |
|---|---|---|
| A | 20 | 28 |
| B | 20 | 14 |
State whether each reaction is exothermic or endothermic. Give a reason for each answer. [2 marks]
(f) Give one advantage of using hydrogen as a fuel. [1 mark]
Question 5 — Rates of reaction and reversible reactions (11 marks)
(a) A student adds magnesium ribbon to excess dilute hydrochloric acid and measures the volume of hydrogen produced.
| Time (s) | 0 | 10 | 20 | 30 | 40 | 50 | 60 |
|---|---|---|---|---|---|---|---|
| Volume of hydrogen (cm³) | 0 | 18 | 31 | 40 | 45 | 48 | 48 |
(i) Name the apparatus used to collect and measure the volume of hydrogen. [1 mark]
(ii) At what time did the reaction stop? [1 mark]
(iii) What volume of hydrogen was produced in the first 20 s? [1 mark]
(iv) Explain why the reaction stopped. [1 mark]
(b) Describe the effect on the rate of the reaction of:
(i) using magnesium powder instead of ribbon [1 mark]
(ii) using acid at a lower temperature. [1 mark]
(c) Give one other way of increasing the rate of this reaction. [1 mark]
(d) Explain why fine flour dust in the air of a flour mill can explode if there is a spark. [1 mark]
(e) Blue hydrated copper(II) sulfate can be heated to form anhydrous copper(II) sulfate. The reaction is reversible.
(i) State the colour of anhydrous copper(II) sulfate. [1 mark]
(ii) Describe what is seen when water is added to anhydrous copper(II) sulfate. [1 mark]
(iii) Give one use of this reaction. [1 mark]
Question 6 — Acids, salts, the Periodic Table and metals (13 marks)
(a) (i) State the colour of universal indicator in a solution of pH 13. [1 mark]
(ii) Name the type of reaction that happens when an acid reacts with an alkali. [1 mark]
(b) Zinc sulfate crystals can be made from zinc carbonate and dilute sulfuric acid. Describe how a student could make pure, dry crystals of zinc sulfate. [4 marks]
(c) Chlorine water is added to colourless potassium iodide solution.
(i) Describe the colour change. [1 mark]
(ii) Explain why the reaction happens. [1 mark]
(d) Give two properties of transition elements that are not shown by Group I metals. [2 marks]
(e) A piece of zinc is placed in blue copper(II) sulfate solution. Predict whether a reaction happens. Explain your answer and describe what is seen. [2 marks]
(f) Explain why steel, rather than pure iron, is used to build bridges. [1 mark]
Question 7 — The environment and organic chemistry (12 marks)
(a) State the approximate percentages of nitrogen and oxygen in clean, dry air. [1 mark]
(b) (i) State how carbon monoxide is formed when fuels are burned. [1 mark]
(ii) Give one harmful effect of carbon monoxide. [1 mark]
(c) (i) Name two greenhouse gases. [1 mark]
(ii) Give one way of reducing the amount of carbon dioxide released into the atmosphere. [1 mark]
(d) Describe two stages in the treatment of water to make it safe to drink, and give the purpose of each. [2 marks]
(e) (i) Give the molecular formula of butane, the alkane with four carbon atoms. [1 mark]
(ii) Name the two products of the complete combustion of butane. [1 mark]
(f) (i) Describe a test to show that ethene is an unsaturated hydrocarbon. Give the result. [1 mark]
(ii) Name the polymer formed from ethene. [1 mark]
(g) Give one use of ethanol. [1 mark]