Approximate Time to Complete: 10-15 Minutes + Questions & Journal Time

About this activity

In this experiment, you will use a balloon that can expand or contract depending on what is inside of it. You will expose that balloon to hot and cold temperatures to see what happens to the balloon and to the air inside.

What you’ll learn

  • Hot air expands, cold air contracts.
  • Empty bottle
  • Balloon
  • 2 bowls
  • Hot water
  • Cold water
  1. Do you remember from the First Great Lesson what happens to particles when they get hot?
  2. Do you remember from the First Great Lesson what happens to particles when they get cold?

Re-watch the First Great Lesson if you need a refresher!

  1. Put the balloon over the bottle opening.
  2. Fill one bowl with hot water.
  3. Fill the other bowl with cold water.
  4. Put the bottom of the bottle into the hot water. Observe what happens to the balloon.
  5. Put the bottom of the bottle into the cold water. Observe what happens to the balloon.

Use these questions as a guide to write a journal entry, make a poster, give a presentation, or write a research report about your experiment or a related topic.

  1. What happened to the balloon when you put the bottle in hot water?
  2. What happened to the balloon when you put the bottle in cold water?
  3. Can you explain what happened to the air inside of the bottle when you put the bottle in hot water, and when you put the bottle in cold water?
  1. What happened to the balloon when you put the bottle in hot water?
    • The balloon should have inflated a little bit. If it didn’t, you may need to use a larger bottle or a smaller balloon.
  1. What happened to the balloon when you put the bottle in cold water?
    • The balloon should have deflated.
  1. Can you explain what happened to the air inside of the bottle when you put the bottle in hot water, and when you put the bottle in cold water?

When you put the bottle into hot water, it heats the air inside of the bottle. When air particles heat up, they spread apart from each other. They want to take up more space. Since the balloon is made of elastic material, it changes shape to allow the air to take up more space.

When you put the bottle into cold water, it cools the air inside of the bottle. When air particles cool, they huddle closer together. They take up less space. They contract. Since the balloon is made of elastic material, it goes back to its original shape.

This experiment explores how temperature affects air. Want to learn more about the properties and movement of air? Take a look at these topics that come with a Learn Libre membership!

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