1. 1
   A student is given a sample of muddy river water and asked to separate the insoluble mud particles from the water. The student pours the mixture through filter paper held in a funnel over a beaker.

   (a)

   What is this technique called?

   [1 mark]

   • AFiltration
   • BDistillation
   • CCrystallisation
   • DChromatography

   (b)

   After filtering the muddy water, what is the correct name for the liquid that has passed through the filter paper?

   [1 mark]

   • AThe residue
   • BThe precipitate
   • CThe filtrate
   • DThe distillate

   (c)

   Define the term mixture, and explain why filtration is a suitable technique for separating the mud from the water in this example.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A chemist wants to obtain solid, pure copper sulfate crystals from a copper sulfate solution. The chemist gently heats the solution to evaporate some of the water, then leaves the remaining solution to cool slowly, allowing crystals to form.

   (a)

   What is this technique called?

   [1 mark]

   • AFiltration
   • BCrystallisation
   • CChromatography
   • DFractional distillation

   (b)

   Why does the chemist evaporate only some of the water, rather than evaporating all of it to dryness, before leaving the solution to cool and crystallise?

   [1 mark]

   • AEvaporating all the water would produce larger, more regular crystals
   • BIt makes no difference how much water is evaporated
   • CEvaporating all the water is required to obtain any crystals at all
   • DEvaporating too much water can decompose the compound or produce small, poorly formed crystals rather than a good, well-formed crystal yield

   (c)

   Describe the steps the chemist should follow to obtain good-quality copper sulfate crystals from the solution, and explain why the solution should be allowed to cool slowly.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A laboratory technician receives a mixture of ethanol and water and needs to separate the ethanol, which has a lower boiling point than water, so it can be recovered as a pure liquid.

   (a)

   Describe the technique the technician should use, and explain how it works.

   [3 marks]

   (b)

   Explain why distillation would not be an appropriate technique if the technician instead needed to separate insoluble sand from a mixture of sand and water, and suggest an appropriate alternative technique with a brief explanation.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A research student is given a complex mixture containing insoluble sand, dissolved copper sulfate, and a small amount of ethanol dissolved in the water. The student is asked to fully separate all three components: the sand, the copper sulfate crystals, and the ethanol.

   (a)

   Describe, in full, a suitable sequence of separation techniques the student could use, explaining the purpose of each step.

   [6 marks]

   (b)

   Evaluate why the order of these separation steps matters, and discuss what problems might arise if the student attempted the steps in a different order, such as trying crystallisation before filtration.

   [6 marks]

   Total for question 4: 12 marks

End of questions