Shrinking Air: Hot vs. Cold

Contributor: Kaitlyn Aston. Lesson ID: 12813

Did you know that hot and cold air are always in a constant battle? No matter what, they are always bumping into each other. Did you know that you could use air to shrink objects? Try it out yourself!


Physics, Physics

learning style
personality style
Golden Retriever
Grade Level
Primary (K-2), Intermediate (3-5)
Lesson Type
Quick Query

Lesson Plan - Get It!


Chloe LOVES ballet. She plans to spend all day practicing for her upcoming performance.

When Chloe gets to the studio, she is hit by a wall of cold air as she walks in the door. After an hour of practicing, Chloe is so cold that she wants to go home. She feels too cold to move!

Have you ever been so cold, like Chloe, that you've been too cold to even move? Have you ever played outside on a cold, snowy day, for so long that all you wanted to do was curl up just to stay warm? If so, then you and molecules have a lot in common!

Just like Chloe, air molecules can become cold, too!

They may not shiver or say they are cold, but you can see it by how the react when they are cooled.

  • What do you think will happen to air molecules when they are cooled?
  • Do they speed up and move around faster, or do they slow down and move around at a slower pace?

In the previous lesson, you saw that warm air was able to take a dent right out of a ping-pong ball, so what do you suppose might happen when something comes in contact with cold air?

Before moving on, if you missed or would like to review the first lessons in our Air series, find them in the Related Lessons in the right-hand sidebar.

Let’s tune in to Flo to see just how it works!


  • Did you see how the sides of the bottle bent in?

This happened because the air molecules, when cooled, pulled in closer together, and therefore took up less space inside the bottle. As this happened, the bottle pulled in as well because the air pressure of the warmer air on the outside of the bottle was greater than the pressure of the cold air inside the bottle.

Once that all makes sense, move on to the Got It? section for a quick quiz!

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