'P' is for Plastic

'P' is for Plastic

When Pam the great magician
Was eating lunch one day,
Some magic fans came over
And would not go away.

The people wanted magic
But what was Pam to do?
She had her plastic lunch bag
And knew some science, too.

With a pencil from her purse
And her bag of plastic,
Take a look at what Pam did —
Totally fantastic!

Why does Pam's plastic bag not spring a leak?

Plastic sandwich bags are flexible and stretching. When a sharp object, like a pencil point, is poked through the bag, the plastic squeezes around the pencil, making a tight, leak-proof seal. It's similar to the way that some tires on cars work. A gummy layer on the inside of the tire seals around any nails or sharp objects poking into the tire.