Sub Unit 1: Visible Holes

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.

Sub Unit 2: Invisible Holes

This sub unit develops on what the student has learned from Visible Holes and focuses on Invisible Holes. To understand the existence of invisible holes and processes of substances being able to pass these holes, students have to enter the world of particles. To introduce them to this “new world”, surprising and fascinating phenomena are used, such as the “sieving of different dyes”. Following this, the students are invited to develop a series of experiments to investigate properties of sieves, particles and diffusion processes.

This can be followed by questions whether all membranes (plastics) are the same (Activity 2.1). Different polymer films can be investigated and polymer films can be made with different levels of plasticizer and retested (Activity 2.5). Do they all have the same structure? Additionally, different compounds can be used on the same films to determine the pore size (Activity 2.2).

As an application, the leaching of plasticisers from packaging will be explored and can link to food packaging and possible hazards (Activity 2.5). Leading questions throughout the unit allow the students to progress from activity to activity as well as develop activities of their own.

Students can examine the uses of holes in dialysis membranes, in polymers used for absorbance, and in other polymer packaging materials.

Sub Unit 3: Interesting Holes

This unit deals with the idea of Interesting Holes which can be used in many medical and environmental technologies. Students can investigate different functional polymers such as superabsorbers and cyclodextrines to find out and explain why these polymers absorb solutions, such as water, or smells. The properties of hydrogels, as drug delivery systems, are investigated.

Nanotechnology can be applied to both medicine and environmental science using silver nanoparticles as an example. These can be incorporated into polymeric membranes which can then be used to treat wounds, burns and infections as the silver ions migrate from the membrane and attack any bacterial or fungal cells. They can also be used to coat different materials to enhance sterility.