Shrinking Bag Experiment

WHAT ARE THE POLYMERS?

Bag of chips is made out of polymers, long chains of molecules.

The word polymer comes from the Greek poly which means many and mer which means parts - so as the name says they are large molecules (macromolecules) composed of smaller units.

Polymers can be both natural, for example DNA and proteins as well as synthetic, most common plastic.

Polyethylene terephthalate (PET) is used for packaging because of its properties: it is lightweight, chemically unreactive, strong and easy to mold into any shape.

The natural state of the polymers is to be bunched up close together. However, when manufacturing bag of chips, to get its expected shape, polymers are stretched out.

SCIENCE BEHIND SHRINKING BAG EXPERIMENT

As we said, the process of manufacturing bag makes polymers stretched out and locks them in that position. But if the material is heated, as we are doing when putting it in the microwave, it releases polymers from their stretched state. They are trying to return to their normal state, close together, so the bag is shrinking.

The bag maintains its shape because polymers are still bound to each other and surrounded by the layer of other materials such as aluminum and paint.

MATERIALS NEEDED FOR SHRINKING BAG EXPERIMENT:

Empty bag of chips
Microwave oven
Tongs

INSTRUCTIONS FOR SHRINKING BAG EXPERIMENT:

Watch the video at the beginning of the article for step by step instructions or continue reading...

Empty the bag of chips and flatten it as much as you can. If it’s too big, cut the top part of it so it fits the microwave oven.
Put it in the microwave oven, and heat it on maximum temperature for 5s. You will notice cracking noise and sparkles coming out of the bag and poof, the bag will shrink.
Carefully, take it out with the help of the tongs - it’s hot!
That’s it - you have a miniature bag of chips! Talk with your child what could be the cause of this “magical” transformation and explore chemical properties of the polymers together.