Learning objectives: 

·        What is filtration
·        How does filtration work
·        What are the best filtration technique
·        What impact on the environment does filtration have
·        Analytic reasoning
·        Sustainability-oriented thinking

Advisable age of students:        10-19
Attention to diversity and inclusion aspects to have in account

Materials:
4 glass jars, a funnel, gravel, sand, 3/4 coffee filters, two types of polluted water (you can put small particles of plastic in one of the polluted waters and muddy in the other one), sieve.
Phase 1      Visualisation   10/20 min

The work of Hong Yi-chen, Guo Yi-hui and Zeng Yu-di called “Pollution” represents the dirty waters of Taiwan. Shown in the form of a popsicle they turn the normal view of something pleasant into something unattractive. Thanks to the unusual form of representing pollution, it brings students to reflect about the importance of environmental awareness. The students should be asked about their general knowledge referring to the topic. The teacher should initiate a conversation about how we can solve and prevent the pollution of waters. Whilst engaging students to talk about the problem the teacher can visualise the ways of dealing with pollution on a whiteboard.

Phase 2.1       Experimentation   Duration 30/40

Build filtration system:
*Prepare the water with mud and add plastic to one of them
*Stack the coffee filters (3-4) on top of the funnel
*Next place a layer of sand and then gravel on the filter
*Place the funnel in one of the empty jars
*In the other one place the sieve
*Pour the muddy water through the funnel and the water with plastic through sieve
*Leave some of the dirty water into the jars to compare the before and after

The difference in the filtration system should be visible. The method of sand and gravel is more effective. Because the sieve stops only the bigger particles of dirt and plastic. This process should help the students understand how mechanical filtrating works. Mechanical filtering is the first step making the water drinkable. The students should differentiate the methods of water filtration. The goal is to be able to explain why one of the methods works better. The teacher should explain that filtering water has a meaning in a bigger scale – the possibility to drink tap water.

Phase 2.2       Experimentation   Duration 20

In the class of minimum 15 students divide the class into four group that will represent the filters, mud, and plastic.

Group 1 – mud (ex. 5 students)
Group 2 – plastic (ex. 5 students)
Group 3 – sand and gravel filters (ex. 1/2 students)
Group 4 – sieves (ex 3/4 students)

The children that represent the two kinds of filters should stand in one line. The objective of the students that represent the mud and plastic is to escape through the children that are the filters. Group 3 can catch both represented pollutions. Group 4 can only catch Group 2. The goal of group 3 is to catch as much of the pollution as possible. The game ends when group 4 catches all of the students who represent plastic or when group 3 catches more than 5 students.  

Phase 3:    Reflexions and debate   Duration 10 min

Ask the students to reflect about the importance of clearing the polluted waters. They should grasp the concept of filtering water on a big scale.
Furthermore, did they apply a logical and analytical reasoning, or did they just follow the rules?
What kind of difficulties did they encountered? How did they manage them? Did this exercise wake up a more sustainability-oriented thinking on some level?

References and links:
“Pollution” byHong Yi-chen, Guo Yi-hui and Zeng Yu-dihttps://edition.cnn.com/style/article/sewage-popsicles-taiwan/index.html