Why Does a Jar Lid Pop When You Open It?

What Crafty Clover says in this video

Intro

Hi there, curious minds! I'm Crafty Clover! Let's discover something amazing. Why does a jar lid pop when you open it?

The Big Idea

A jar lid pops because air rushes in when the seal breaks! Inside a sealed jar, the air pressure is lower than outside. The outside air pushes the lid down tight until you open it.

Sealed at the Factory

Step one: sealed tight. When a jar is sealed at the factory, the air inside ends up at a lower pressure than the air outside. That is because the food is packed warm, and as it cools, the air inside takes up less space.

Outside Pushes

Step two: the outside pushes. The air outside pushes the lid down tightly. That is why a new jar can be hard to open.

The Pop

Step three: the pop. When you break the seal, outside air rushes in. The quick jump in air pressure is the popping sound.

A Closer Look

Let's take a closer look! The jar is sealed tight. Many have a button that is pushed down. When the seal breaks, the button pops up. That is when air rushes in and pops.

Quick Facts

Quick facts! The button on top pops up when the seal breaks. If the button is already popped up, the jar may not be safe, so tell a grown-up. The pop happens just once, because the air pressure is then equal. Ask a grown-up to open jars, so no one gets hurt.

Think Like a Scientist

Now, take the mission! Look at a new jar with a safety button. Press the dome and listen for the click. Ask a grown-up to open a new jar and listen for the pop. Why does the pop happen only once?

Outro

A jar lid pops when outside air rushes in. Science is amazing! Crafty Clover can be found on Amazon Books, Google Bookstore, and Apple Books. Available for purchase or download! Bye for now!