Science is Magic

59

SCIENCE

PART...

THE

3

Keep adding more

pencils. The bag

will never leak!

The bag doesn’t leak because

plastic is stretchy. Let’s compare

pencils going through a sheet

of paper and a plastic bag...

PAPER

PLASTIC

When you poke

a pencil through

paper, it rips, and

gaps form around

the pencil. If this

was a paper bag full

of water, the water

would leak out

through these gaps.

Instead of ripping,

plastic stretches and

moves to make room

for the pencil. This

creates a tight seal

so the water can’t

leak out.

When you stretch an

elastic band, it tightens

against what’s underneath

it. This is what the plastic

does around the pencil.

Plastic is stretchy like an elastic

band—when it wraps around

something, it squishes it.

US_058-059_Magic_no_leak_bag.indd 59 12/09/2018 15:50