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InkFlaskCambridge IGCSE

Separate · Biology · Chemistry

Filter funnel and paper

Filter funnel and paper, with labels: filter paper, folded into a cone, filter funnel, stem, the filtrate drips out here.

What it is for

Separates an insoluble solid (residue) from a liquid (filtrate).

Mistake to avoid Filling above the top of the filter paper, so liquid and solid run down between the paper and the funnel into the filtrate.

How it is asked

  • Name the method, filtration, and label a diagram: filter funnel, filter paper, residue and filtrate.
  • Choose filtration to separate an insoluble solid from a liquid, such as sand from salt solution or excess solid from a salt solution.
  • Explain why the residue is washed with a little distilled water and then dried.

Exam-style question

A student has a mixture of sand and salt and wants a sample of dry, clean sand.

  1. Describe how the student separates the sand.
  2. Name the filtrate.
  3. Why is the liquid kept below the top of the filter paper?
Show what a good answer says
  1. Add water and stir, so the salt dissolves; filter; the sand stays on the paper as the residue; wash it with a little distilled water, then dry it.
  2. Salt (sodium chloride) solution: the dissolved salt passes through the paper with the water.
  3. Above it, the mixture runs down between the paper and the funnel, so sand gets into the filtrate.

Teaching points for checking your own answer, not official Cambridge marks.

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