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Weather Academy: Balloon Air Pressure Experiment

Published: Jan. 10, 2022 at 6:33 AM CST
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MONROE, La. (KNOE) - Today we’re gonna be doing an experiment that’s going to help demonstrate the power of pressure. This will be a refresher before we dive into next week’s topic of bomb cyclogenesis.

What you’ll need:

  • 1 one large glass jar
  • One balloon
  • Water
  • Funnel
  • A bit of paper
  • Matcher or a lighter

Steps:

  1. Fill the balloon with water until it’s a little too big to fit through the mouth of the jar.
  2. Place the balloon on top of the jar to show that it won’t fit into the jar, push down slightly to show that it won’t fit.
  3. Remove the balloon from the jar.
  4. Light a bit of paper on fire and drop it into the jar
  5. Quickly place the balloon on top of the jar
  6. Step back and observe

Why does this happen?

This experiment shows the power of air pressure. When we first place the balloon on top of the jar, the air pressure inside the jar prevents the balloon from being pushed inside. The air inside of the mason jar has nowhere to go because the balloon is covering the opening. The air pressure inside the jar is equal to the air pressure outside the jar.

When we add the lit piece of paper into the jar, it creates hot air. The warm air is expanding and creating an area of low pressure. The air will begin to rise and escape around the sides of the balloon. You will start to see the balloon shake as the air escapes around it.

The balloon acts as a one-way valve, allowing the warm air inside the jar to escape but preventing any new air from entering the jar. With less air in the jar, the air pressure drops and becomes lower than the air outside the jar. This causes the balloon to get sucked in.

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