This subunit introduces the idea of “holes” in materials which we can see and use on a daily basis. These holes are used in sieves, as a means of separation e.g. large stones from sand, coffee filters, muslin in cheese production etc. The idea that there is a lack of holes in some materials should also be discussed as well as their uses.
The learning outcome of this sub unit is that students recognise that holes exist in many materials, and can be used to separate substances. However, the separation depends on both the size of the holes and the sizes of the substances to be separated.
This subunit can also be used to introduce the concept of osmosis and diffusion.