Warm Air Rises to the Top

Contributor: Nichole Brooker. Lesson ID: 11843

Have you ever watched flames and smoke? What direction do they go? Why do you think that is? It's because warm air rises! Put on your scientist hat and try a fun (and safe) experiment with balloons!


Physical Science

learning style
personality style
Grade Level
Primary (K-2)
Lesson Type
Quick Query

Lesson Plan - Get It!


Have you ever gone up to the second floor of a house or apartment building and felt that it was warmer there than downstairs? How do you explain that?

Have you ever wondered why it was warmer on an upper floor of a house or apartment building?

Have you ever sat in a basement or ground floor room and were cold, but after going upstairs, you were warm? This is what happens to warm air! It rises, or goes up.

Now, you may wonder why warm air goes up. You may think it has something to do with getting closer to the sun, but that isn't really the case.

The reason warm air rises is the same reason oil sits on top of water when you pour them together. Oil is lighter than water, so it sits on top of the water when the two are put in the same container. (NOTE: To learn more about this effect, visit the Elephango lesson found under Additional Resources in the right-hand sidebar.)

Similarly, when air, or any other gas, is heated, it expands. When air expands, the molecules spread apart and become less dense, or lighter than the air around them, so the air floats upwards.

A really good example of hot air rising is a hot air balloon. Have you ever seen a hot air balloon in person?

A hot air balloon is made of a basket to carry the people, ropes to connect the basket to the balloon, and fire! When the fire heats the air inside the balloon, it makes it float into the sky!

  1. Watch How Do Hot Air Balloons Work? (below) to learn all about hot air balloons.
  2. Print four copies of Draw and Describe How Hot Air Rises found in Downloadable Resources in the right-hand sidebar.
  3. After you watch the video, draw a series of four pictures to explain how hot air balloons work.
  4. Label the parts of your pictures and share your pictures with your teacher or parent.
  5. You will use these pictures in the next section as well.


WOW! Isn't it fascinating that the air that we are breathing right now can also make a hot air balloon float? Science is so cool!

Since warm air takes up more space than cold air, later in this lesson, you will get to experience how that happens. First, though, you need to review what you've learned.

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