Stick to the Point!

In this demo experiment from our school workshop series, you will find out about the physics of how plastics or polymers stretch and bend.

What you need

Sharp pencils, zip-lock bag, water, basin or better to do it outside

Watch the video and try this at home!

(Video made by Cillian Fahy)

Here’s the science…

The plastic in a zip-lock bag is made of polymers which are long chains of molecules. When you poke the sharp pencil into the bag, the polymers move apart but then the flexibility of the polymers push back toward the pencil and form a temporary seal, so the water inside does not pour out when the bag is pierced. When you remove the pencil, you expose the hole in the bag and the water pours out.

Can you think of other times when you have seen how polymers stretch? What other types of stretchy polymers might you use on a daily basis?

Uses of Stretchy Polymers

We’ve probably all used cling-film at home to wrap up food. Cling-film is also a stretchy polymer which let’s you stretch it to cover an item well so that no air can get in and preserve it better.