Learning Aims:
This sub-unit will illustrate how different materials can be used as sieves. Separation depends on the hole size in the ‘sieve’ as well as the particle size of the compounds/materials to be separated. Hence this subunit focuses on the microscopic properties and structures.

  • to recognize the need for holes to separate materials
  • to recognize the need for particular size of holes matching the size of the materials to be separated
  • to construct a model and debate with peers
Mixture of different sized seeds (or the like), filter paper, scissors, containers, “distractors”, such as magnet, glue…
Suggestions for use:

Present students with the challenge to separate the seeds without touching the seeds using some of the materials provided. We expect at least some students to come up with the idea of sieves. Of course they can also discuss other methods of separation. If the idea of preparing a sieve from the paper does not arise, discussion can be directed towards the use of sieves in everyday applications.

Possible questions:
  • Why did you create your technique as you did?
  • What are the advantages and disadvantages of your technique compared to others?
  • What do you already know about separation procedures in every-day life?