Monday, June 22, 2020

Sustainable Stories: Which Plastic?

This blog post is brought to you by Jane Winter, one of our advisory teachers who works in Lincolnshire and Yorkshire.

Although the materials for this investigation are free and readily available, they can be a little tricky to source.  However, it is well worth taking the trouble to do this as, once you have, everything else is very straightforward.  When I have done this activity I have found that there is a real buzz in the classroom.  Moreover, you could easily provide enough equipment for a whole classroom full of socially distanced youngsters to do the activity at the same time.

The tricky bit

You will need samples of some different types of plastic. 
Sample 1: The thin clear plastic that often comes around packs of Christmas cards and in some other packaging
 Sample 2: Foam plastic (expanded polystyrene, PS) used as for takeway foods such as burgers and chips
Sample 3: Polystyrene, as used for the lids of takeaway coffee cups. The name of this plastic surprises the children, as ‘expanded’ polystyrene is commonly referred to as polystyrene, but for scientists, there are two types, and this one is un-expanded!
Sample 4: The plastic used for milk bottles (polythene, HDPE)

Each child will need a strip of each plastic cut to approximately 8 x 1 cm.  They will also need a bowl, jug or tub of water large enough to put their hand into and some table salt.

Top Tip 
This is one activity that you really must try out for yourself before letting your class lose with it.  Manufacturers sometimes change the formulation of their plastics and so they don’t always behave as you expect them to!

The fun bit
Children test each sample to see if it floats in water or in salt solution (brine) and how it reacts to being folded.  The results of their tests will let them identify what each sample of plastic is made of.  For example, PVC and polystyrene will both sink in plain water; but if salt is added the polystyrene will begin to float.
This is an important thing to be able to do as different plastics are recycled in different ways so we need to be able to identify them.  At this stage I have found that providing children with a simple table helps them to organise their data as they carry out the tests.  

Full instructions, including safety notes, for how to do the activity are provided in this free to download resource.

This activity builds on the work that children have done on materials in KS1. It helps them to develop their skills of working scientifically by sorting in a more sophisticated way.  There is a simple sorting key on activity sheet 5 of the resource which will support children develop their understanding of how keys work, as they use it to classify their plastic samples.

As children start to think about the reasons that we might need to be able to classify materials more precisely they can begin to consider why and how this science might be used in industry.  A class discussion will help them to understand that being able to use post-consumer waste makes processes more economically viable as well as more environmentally friendly.  These sorts of links help to raise children’s science capital as they see how the science that they do in school has real life applications and is relevant to their lives both now and in the future.

To coincide with InternationalWomen in Engineering day we have published a new IndusTRY AT HOME activity for you share with families.  Why don’t you put a link on your school website?

For a broader set of activities linked to this topic, please go to which expands the topic to look at the heat insulation and shock absorption properties of plastics – and children design and test packaging to protect parcels of fragile crisps, which they post back to themselves in school – the ultimate test of their designs!

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