Purity and separating mixtures: OCR GCSE Combined Science A questions

Every OCR GCSE Combined Science A exam question on C2.1 Purity and separating mixtures, 2018–2025, with its mark scheme and examiner’s report.

All 62 questions on Purity and separating mixtures, as a list

June 2025, Chemistry Paper 3 Foundation, Q6 (1 mark): Which type of mixture can be separated using paper chromatography? A A mixture of gases. B A mixture of insoluble liquids. C A mixture of insoluble solids. D A
June 2025, Chemistry Paper 3 Foundation, Q9 (1 mark): Which statement describes a pure substance? A A mixture of substances which melts at a single temperature. B A mixture of substances which melts over a range of
June 2025, Chemistry Paper 3 Foundation, Q15(d) (2 marks): The student separates the salt from the solution formed at the end of the reaction. Step 1: They remove the excess magnesium carbonate. Step 2: They remove the
June 2025, Chemistry Paper 9 Higher, Q1 (1 mark): Which statement describes a pure substance? A A mixture of substances which melts at a single temperature. B A mixture of substances which melts over a range of
June 2025, Chemistry Paper 9 Higher, Q7 (1 mark): A student performs a chromatography experiment on a mixture of dyes. The solvent moves 8.0 cm up the chromatography paper. The Rf value for one dye is 0.60. Wha
June 2024, Chemistry Paper 3 Foundation, Q7 (1 mark): Which row describes a formulation? Description Amount of chemicals A compound exact B mixture exact C compound random D mixture random Your answer [1]
June 2024, Chemistry Paper 3 Foundation, Q13(a)(i) (1 mark): What name is given to this method of separation? Tick (3) one box. Crystallisation Distillation Filtration [1]
June 2024, Chemistry Paper 3 Foundation, Q13(a)(iii) (1 mark): After several minutes the glass tube becomes hot, and no more water is collected in the test tube. Give one reason why the glass tube becomes hot. [1]
June 2024, Chemistry Paper 3 Foundation, Q13(a)(iv) (1 mark): The student wants the experiment to work for longer. What other piece of equipment can they use instead of the glass tube? [1]
June 2024, Chemistry Paper 3 Foundation, Q13(b)(i) (1 mark): The student draws a bar chart of the results. Draw a bar on the bar chart for the results when 4 g of salt are added to the ice. Mass of salt (g) 1 2 3 4 0 –1 –
June 2024, Chemistry Paper 3 Foundation, Q13(b)(ii) (1 mark): Describe how changing the mass of salt changes the melting point. [1]
June 2024, Chemistry Paper 3 Foundation, Q13(b)(iii) (1 mark): The student thinks the results show that pure ice will have a melting point of 0 °C. Explain why the student is correct. [1]
June 2024, Chemistry Paper 3 Foundation, Q14(a) (1 mark): Which food colouring contains the most dyes? [1]
June 2024, Chemistry Paper 3 Foundation, Q14(b) (1 mark): Which food colourings contain the same dye? [1]
June 2024, Chemistry Paper 3 Foundation, Q14(c) (1 mark): The teacher repeats the experiment with a new food colouring Q. They find it contains the same dyes that are also found in B and D. Draw the results for the foo
June 2024, Chemistry Paper 3 Foundation, Q14(d) (3 marks): Fig. 14.3 shows the result for the food colouring D. Fig. 14.3 Solvent front 49 mm 37 mm Base line D Calculate the Rf value for the dye in the food colouring. G
June 2024, Chemistry Paper 4 Foundation, Q11(a)(i) (1 mark): What is the name of this separation technique? [1]
June 2024, Chemistry Paper 4 Foundation, Q11(b) (2 marks): Fig. 11.2 shows the equipment the student uses in their second experiment. Fig. 11.2 A cold, curved Large metal tin piece of glass Glass beaker Muddy water Wate
June 2024, Chemistry Paper 9 Higher, Q3 (1 mark): The graph shows how the temperature of two samples of a substance, Y and Z, changes as they melt from solids to liquids. Z Temperature (°C) Y Time (minutes) Whi
June 2024, Chemistry Paper 10 Higher, Q12 (4 marks): A student does an experiment to separate water from muddy water. The diagram shows the equipment they use. A cold, curved Large metal tin piece of glass Glass b
June 2023, Chemistry Paper 3 Foundation, Q6 (1 mark): The diagram shows how paper chromatography can be used to separate the colours in an ink. Filter paper Spot of ink Solvent What is the solvent called? A The bas
June 2023, Chemistry Paper 3 Foundation, Q9 (1 mark): Which substance is described as pure by a scientist? A A solution of sodium chloride B An alloy C Dilute sulfuric acid D Distilled water Your answer [1]
June 2023, Chemistry Paper 3 Foundation, Q13 (6 marks): 13* A student has a mixture of sand and a salt solution. Salt solution Sand They do a two stage experiment to obtain a sample of pure salt from the mixture. Des
June 2023, Chemistry Paper 9 Higher, Q1 (1 mark): Which substance is described as pure by a scientist? A A solution of sodium chloride B An alloy C Dilute sulfuric acid D Distilled water Your answer [1]
June 2023, Chemistry Paper 9 Higher, Q6 (1 mark): Which diagram shows the correct equipment diagram for simple distillation? A Water out Water in B Water in Water out C Water out Water in D Water in Water out Y
June 2023, Chemistry Paper 9 Higher, Q12(a) (2 marks): Identify the stationary phase and mobile phase shown in Fig. 12.1. Stationary phase Mobile phase [2]
June 2023, Chemistry Paper 9 Higher, Q12(b) (1 mark): What determines how far the sample travels up the TLC plate? Tick (3) one box. The amount of sample used. The size of the TLC chamber. The type of solvent used.
June 2023, Chemistry Paper 9 Higher, Q12(c)(i) (3 marks): Calculate the Rf value for the sample. Give your answer to 2 decimal places. Rf value for sample = [3]
June 2023, Chemistry Paper 9 Higher, Q12(c)(ii) (1 mark): The table shows the Rf values for four different substances. Substance Rf value A 0.23 B 0.57 C 0.30 D 0.18 Use your answer to (i) to identify which substance,
June 2022, Chemistry Paper 3 Foundation, Q1 (1 mark): A black ink is a mixture of different colours. The diagram shows how the colours in the black ink can be separated. Strip of filter paper Black ink Water What i
June 2022, Chemistry Paper 3 Foundation, Q11(c)(ii) (1 mark): A scientist measures the melting point of a sample of nitrogen dioxide. The result shows that the sample of nitrogen dioxide is impure. Which temperature could
June 2022, Chemistry Paper 3 Foundation, Q14 (6 marks): 14* A student wants to produce a pure dry sample of the salt sodium chloride. The diagram shows the method they use. 2 cm3 portions of Solution formed sodium hy
June 2022, Chemistry Paper 9 Higher, Q4 (1 mark): Which substance is an example of a formulation? A A macromolecule B A metal C An alloy D An ionic compound Your answer [1]
June 2022, Chemistry Paper 9 Higher, Q5 (1 mark): The diagram shows a chromatogram produced by paper chromatography. Solvent front 15 cm 10 cm Base line What is the Rf value? A –10 B –5 C 0.67 D 1.5 Your answer
November 2021, Chemistry Paper 3 Foundation, Q4 (1 mark): Which substance is a formulation? A Air B An alloy C Carbon dioxide D Distilled water Your answer [1]
November 2021, Chemistry Paper 3 Foundation, Q11 (4 marks): Different separation techniques are used to separate different types of mixtures. Draw lines to connect each separation technique with its correct description.
November 2021, Chemistry Paper 3 Foundation, Q14(c)(i) (1 mark): State the letter, A, B, C or D, of one pure substance in the table. [1]
November 2021, Chemistry Paper 3 Foundation, Q14(c)(ii) (1 mark): State a reason for your answer to (c)(i) using information from the table. [1]
November 2021, Chemistry Paper 9 Higher, Q5 (1 mark): A scientist wants to find out the amount of each chemical in a mixture. Which row in the table shows the chromatographic techniques that the scientist could use
November 2020, Chemistry Paper 3 Foundation, Q1 (1 mark): The diagram shows how pure water can be separated from salt water by simple distillation. Condenser Purewater Salt water Heat Which two changes of state happen
November 2020, Chemistry Paper 3 Foundation, Q13(a) (1 mark): What is the name of this method of separation? Tick (V) one box. Chromatography Crystallisation Distillation Filtration [1]
November 2020, Chemistry Paper 3 Foundation, Q13(b)(i) (1 mark): What is the mobile phase in the experiment? [1]
November 2020, Chemistry Paper 3 Foundation, Q13(b)(ii) (1 mark): Give a reason why the student chose the substance in (b)(i) as the mobile phase. [1]
November 2020, Chemistry Paper 3 Foundation, Q13(c) (1 mark): The student knows that the R, value of a different dye is 0.46. She thinks that this R, proves that the dye is the same orange dye found in the black ink. Do yo
November 2020, Chemistry Paper 3 Foundation, Q13(d) (3 marks): Another student repeats the experiment but uses a pure blue ink. He measures the distance travelled by the blue ink and the water. Look at Table 13.2. It shows
November 2020, Chemistry Paper 3 Foundation, Q16(a): What is the name given to a mixture, such as perfume, where the ingredients are combined in exact amounts? ...1]
November 2020, Chemistry Paper 3 Foundation, Q16(b) (2 marks): A bottle contains 25g of the perfume. Calculate the mass of water in 25g of the perfume. Mass of water in 25g of perfume = .. [2]
November 2020, Chemistry Paper 9 Higher, Q11(a) (1 mark): What is the name given to a mixture, such as perfume, where the ingredients are combined in exact amounts? [1]
November 2020, Chemistry Paper 9 Higher, Q11(b) (2 marks): A bottle contains 25 g of the perfume. Calculate the mass of water in 25 g of the perfume. Mass of water in 25 g of perfume = [2]
June 2019, Chemistry Paper 3 Foundation, Q14(b)(i) (1 mark): Explain the meaning of the term pure. [1]
June 2019, Chemistry Paper 3 Foundation, Q14(b)(ii) (1 mark): Three students, A, B and C make aspirin and check its purity. The students test the purity of the aspirin by measuring the melting point. Their results are show
June 2019, Chemistry Paper 3 Foundation, Q14(c) (2 marks): Another method of checking the purity of a substance is paper chromatography. Look at the diagram of the apparatus used for paper chromatography. Label the chro
June 2019, Chemistry Paper 3 Foundation, Q14(d) (6 marks): Aspirin is a widely used painkiller and is sold as tablets. One of the chemicals in aspirin is salicylic acid. The structure of salicylic acid is shown below. H
June 2019, Chemistry Paper 3 Foundation, Q15(a) (1 mark): How could the student separate the copper from the solution? [1]
June 2019, Chemistry Paper 9 Higher, Q4 (1 mark): Which separation technique in the laboratory requires a condenser? A Chromatography B Crystallisation C Filtration D Distillation Your answer [1]
June 2019, Chemistry Paper 9 Higher, Q12 (6 marks): 12* A student carries out an experiment using paper chromatography to distinguish between three substances. Here is his method. 1. Draw a pen line half way up t
June 2018, Chemistry Paper 3 Foundation, Q1 (1 mark): A student wants to make solid ammonium sulfate from the solution of ammonium sulfate. What should the student do first? A Distil the solution. B Evaporate the s
June 2018, Chemistry Paper 3 Foundation, Q4 (1 mark): A student wants to re-crystallise a solute from a solution. What type of apparatus should she use? A An evaporating dish, wire gauze, tripod and Bunsen burner B
June 2018, Chemistry Paper 3 Foundation, Q11(a) (2 marks): A student wants to accurately measure the melting point of ice. Describe an experiment that she could do. You may draw a labelled diagram to help your answer. U
June 2018, Chemistry Paper 3 Foundation, Q11(b) (1 mark): Suggest one thing the student could do to improve the experiment. [1]
June 2018, Chemistry Paper 3 Foundation, Q17 (6 marks): 17* A student wants to find out which pigments are in a plant. She does a chromatography experiment on a sample from the plant. Look at her results. 10 9 Solven
June 2018, Chemistry Paper 9 Higher, Q7 (1 mark): Which statement best describes the stationary phase in thin layer chromatography (TLC)? A A glass plate with chromatography paper B Alumina powder in ethanol C

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