Air in Balloon in Air, Winds And Cyclones – Class 7 Science Experiment

Chapter Name: Air, Winds And Cyclones

Activity Name: Air in Balloon in Air, Winds And Cyclones

Activity Description:

In this experiment, we will observe the behavior of air inside a balloon when it is heated slowly. Additionally, we will investigate what happens when the tied end of the balloon is opened after it has been heated.

Required Items:

  1. Balloon
  2. Heat source (e.g., a candle or hot water)

Step by Step Procedure:

  1. Take a balloon and tie one end securely to prevent the air from escaping.
  2. Fill the balloon with air by blowing into it or using a pump.
  3. Hold the balloon above a heat source (e.g., a candle flame or immerse it in hot water) and heat it slowly.
  4. Observe what happens to the balloon as it is heated.

Experiment Observations:

As the balloon is heated, it expands and becomes larger in size. This expansion occurs because the air molecules inside the balloon gain energy and move more vigorously, exerting increased pressure on the walls of the balloon. Consequently, the balloon stretches to accommodate the increased volume of air.

• If the tied end is opened now, what would happen? When the tied end of the balloon is opened, the air inside the balloon would start to escape gradually.

• Why does that happen? This happens because the air inside the balloon is at a higher pressure than the surrounding air. When the tied end is opened, the pressurized air inside the balloon rushes out to equalize the pressure with the surrounding air. As a result, the balloon deflates.


  1. Be cautious while heating the balloon to avoid burns or accidents.
  2. Ensure that the balloon is not over-inflated, as it may burst when heated.

Lesson Learnt from Experiment:

The experiment demonstrates the properties of gases, where heating air causes it to expand due to increased molecular movement and pressure. When the tied end of the balloon is opened, the air escapes, seeking equilibrium with the surrounding air.

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