Pearson Edexcel International GCSE Chemistry 4CH1: States of matter; elements, compounds and mixtures – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover sub-topics 1(a) States of matter and 1(b) Elements, compounds and mixtures (points 1.1 to 1.13) of the Pearson Edexcel International GCSE Chemistry (4CH1) specification, Issue 3 (September 2024). The qualification is untiered. Points 1.5C to 1.7C carry a C reference, so they are Paper 2 only; questions 8 and 9 are labelled. A calculator may be used on both papers.

Learn the content first in the study guide and revision notes for this unit. They do not repeat the Principles of chemistry practice set. Course hub: Edexcel IGCSE Chemistry; printable checklist.

Questions

1. Name each change of state.

(a) Liquid wax turning into solid wax. [1] (b) Steam turning into water on a cold window. [1] (c) Solid carbon dioxide turning directly into a gas. [1]

2. A pure solid is heated steadily. Its temperature stays at 54 °C until it has all melted, then rises again.

(a) Explain why the temperature stays at 54 °C during melting. [2] (b) Describe the changes in the arrangement, movement and energy of the particles as the solid melts. [3]

3. A student dissolves a few crystals of purple potassium manganate(VII) in 10 cm³ of water. She takes 1 cm³ of this solution and makes it up to 10 cm³ with water. She repeats this with each new solution.

(a) After four dilutions the solution is still pale purple. Explain what this suggests about the particles in the crystals. [2] (b) State what fraction of the original concentration is left after four dilutions. [1] (c) A crystal is dropped into a beaker of still water. Explain why, after an hour, purple colour has spread through the water without stirring. [2]

4. A gas jar of air is placed upside down on top of a gas jar of brown bromine vapour. The glass cover between them is removed.

(a) Describe what you would see after 30 minutes. [1] (b) Explain this observation in terms of particles. [2] (c) The experiment is repeated at a higher temperature. State and explain the effect on the time taken. [2]

5. For each substance, state whether it is an element, a compound or a mixture.

(a) Nitrogen, N₂ [1] (b) Ammonia, NH₃ [1] (c) Sea water [1] (d) Brass, made of copper and zinc not chemically combined [1] (e) Iron and sulfur can be heated together to form iron(II) sulfide. Give two ways in which iron(II) sulfide differs from a mixture of iron and sulfur. [2]

6. Two white solids are tested. Solid A melts sharply at 122 °C. Solid B melts gradually between 114 °C and 119 °C. A sample of water boils at 102 °C at normal atmospheric pressure.

(a) State which solid is pure and give a reason. [2] (b) Suggest what the boiling point tells you about the water sample. [1]

7. Name the best method to obtain:

(a) sand from a mixture of sand and water [1] (b) pure water from copper(II) sulfate solution [1] (c) propanone from a mixture of propanone and water, which mix completely [1] (d) crystals of potassium nitrate from potassium nitrate solution [1] (e) the separate dyes in a black ink [1]

8. (Paper 2 only) A student finds the solubility of a salt in water at 40 °C. Her results:

Measurement	Mass / g
Empty evaporating basin	41.20
Basin + saturated solution	66.70
Basin + solid after first heating	46.42
Basin + solid after second heating	46.30
Basin + solid after third heating	46.30

(a) Explain why she heated the basin three times. [2] (b) Calculate the solubility of the salt at 40 °C in g per 100 g of water. [3] (c) State how she made sure the solution was saturated. [1]

9. (Paper 2 only) The solubility of salt Y is shown.

Temperature / °C	10	30	50	70	90
Solubility / g per 100 g water	22	37	58	85	118

(a) State the quantity you would plot on each axis to draw a solubility curve. [1] (b) Describe how the solubility of Y changes with temperature. [1] (c) A saturated solution of Y in 40 g of water at 70 °C is cooled to 10 °C. Calculate the mass of crystals that forms. [3] (d) 20 g of Y is stirred into 50 g of water at 30 °C. Show whether all of it dissolves. [2]

10. A student has a mixture of sand and copper(II) sulfate. Copper(II) sulfate dissolves in water; sand does not.

(a) Describe how she can obtain dry crystals of copper(II) sulfate from the mixture. [5] (b) She now wants pure water from some copper(II) sulfate solution. Name the method and explain how the water is separated. [2]

11. A food colouring E is tested by paper chromatography with water as the solvent. The solvent front moves 7.5 cm. E gives three spots: one stays on the baseline, one moves 1.8 cm and one moves 4.5 cm. Reference dyes have these Rf values: P 0.24, Q 0.60, R 0.80.

(a) Explain why the baseline is drawn in pencil. [1] (b) Explain why the solvent must start below the baseline. [1] (c) Calculate the Rf value of each moving spot. [2] (d) Identify the dyes present in E. [1] (e) Explain the spot on the baseline. [1] (f) State the minimum number of substances in E. [1]

Answers

1. (a) Freezing [1] (b) Condensing [1] (c) Sublimation [1] Examiner insight: one-word answers score here, but “evaporation” for (b) or “melting” for (c) gets no credit because each mark needs the exact named change.

2. (a) The energy supplied is used to overcome the forces between the particles [1], not to increase their kinetic energy, so temperature does not rise [1]. (b) Arrangement changes from regular to irregular, particles still close [1]; movement changes from vibrating about fixed positions to moving around each other [1]; particles gain energy [1]. Examiner insight: (b) needs three separate points; “the particles move faster” alone covers only one of them.

3. (a) The crystals contain a very large number of particles [1] which are very small, so they still colour the water after spreading out [1]. (b) 1/10 × 1/10 × 1/10 × 1/10 = 1/10 000 [1] (c) The particles move randomly [1] and spread from high concentration to low concentration by diffusion [1]. Examiner insight: “particles spread out” without random movement or a concentration gradient is too vague for credit.

4. (a) Both jars are the same pale brown colour [1]. (b) Bromine and air particles move randomly [1], so they mix until evenly spread (diffusion) [1]. (c) The time is shorter [1] because the particles have more energy and move faster [1]. Examiner insight: in (c) the effect and the reason are separate marks; “it is faster” alone scores one, and the reason must mention particles having more energy or moving faster.

5. (a) Element [1] (b) Compound [1] (c) Mixture [1] (d) Mixture [1] (e) Iron(II) sulfide has fixed proportions of iron and sulfur [1]; it has different properties from iron and sulfur, e.g. it is not magnetic [1]. (Also accept: it can only be split up by a chemical reaction, not by a magnet.) Examiner insight: “it has two elements” earns nothing in (e), because a mixture of iron and sulfur also contains two elements.

6. (a) Solid A [1]: a pure substance has a fixed (sharp) melting point; B melts over a range so it is a mixture [1]. (b) It is impure (contains dissolved substances) [1]. Examiner insight: naming A without a reason earns only one mark; the reason must refer to a fixed melting point or to B melting over a range.

7. (a) Filtration [1] (b) Simple distillation [1] (c) Fractional distillation [1] (d) Crystallisation [1] (e) Paper chromatography [1] Examiner insight: “distillation” without “simple” or “fractional” may not be accepted in (b) and (c), where the type of distillation is the point being tested.

8. (a) To make sure all the water had evaporated [1]; the mass stopped changing (heated to constant mass) [1]. (b) Mass of solid = 46.30 − 41.20 = 5.10 g [1] Mass of water = 66.70 − 46.30 = 20.40 g [1] Solubility = 5.10 ÷ 20.40 × 100 = 25.0 g per 100 g of water [1] (c) Undissolved solid was still present (excess solid added and stirred at 40 °C) [1]. Examiner insight: using the first-heating mass (46.42 g) loses the accuracy mark, but method marks can still be awarded.

9. (a) Solubility (g per 100 g water) on the y-axis and temperature (°C) on the x-axis [1]. (b) Solubility increases as temperature increases [1]. (c) Difference per 100 g = 85 − 22 = 63 g [1] Scale to 40 g of water: 63 × 40 ÷ 100 [1] = 25.2 g [1] (d) 50 g of water at 30 °C dissolves at most 37 × 50 ÷ 100 = 18.5 g [1]; 18.5 g < 20 g, so not all dissolves (1.5 g remains) [1]. Examiner insight: in (c), 63 g without scaling to 40 g of water scores the first mark only; the final answer needs the scaling step shown.

10. (a) Add water and stir (warm) so the copper(II) sulfate dissolves [1]. Filter; sand stays on the filter paper [1]. Heat the filtrate to evaporate some water until it is saturated (crystals form on a glass rod) [1]. Leave to cool so crystals form [1]. Filter off the crystals and dry them between filter papers [1]. (b) Simple distillation [1]; the water boils off as steam, is cooled and condensed in the condenser and collected, while the copper(II) sulfate stays in the flask [1]. Examiner insight: evaporating to dryness instead of crystallising usually loses the cooling mark, because the question asks for crystals.

11. (a) Pencil does not dissolve in the solvent, so it will not run [1]. (b) Otherwise the spots would dissolve into the solvent instead of moving up the paper [1]. (c) 1.8 ÷ 7.5 = 0.24 [1]; 4.5 ÷ 7.5 = 0.60 [1] (d) P and Q [1] (e) That substance is insoluble in water (the solvent) [1]. (f) 3 [1] Examiner insight: an Rf above 1 means the division is upside down and loses the calculation marks; measure both distances from the baseline.

Where marks are usually lost

• Leaving out energy when describing a change of state.
• Saying temperature rises during melting.
• Explaining diffusion without random movement of particles.
• Giving “evaporation” when the change is condensing, or “melting” for sublimation.
• (Paper 2 only) Dividing by the mass of the solution, not the water, or using a mass before constant mass was reached.
• (Paper 2 only) Forgetting to scale crystal masses to the actual mass of water.
• Saying a compound “contains two elements” as the difference from a mixture.
• Writing “distillation” without saying simple or fractional.
• Measuring Rf from the bottom of the paper, not the baseline.
• Not counting a spot left on the baseline as a substance.

Next steps

• Revise from the revision notes for this unit.
• Re-read any weak sections in the study guide for this unit.
• Formulae, equations and calculations practice.
• Take the free 4CH1 all-topics diagnostic.
• See the course hub and the printable checklist.
• Book a free trial class.

Official syllabus

Pearson Edexcel International GCSE in Chemistry (4CH1) specification, Issue 3, September 2024, Pearson Education Limited. Topic 1 Principles of chemistry, sub-topics (a) States of matter and (b) Elements, compounds and mixtures, points 1.1–1.13.